Si4468/7 H I G H - P ERFORMANCE , L O W -C U R R E N T T RANSCEIVER Features XIN XOUT 20 19 18 17 16 RXp 2 Applications 1 15 nSEL RXn 3 Smart metering (802.15.4g and WMBus) 802.15.4 mesh networking Home security and alarm Telemetry Garage and gate openers Star and point-to-point networks Home automation Ultra narrowband, long range applications Industrial control Sensor networks Health monitors Electronic shelf labels Low power wireless sensor nodes Description 14 SDI GND PAD TX 4 13 SDO NC 5 12 SCLK 6 7 8 9 10 GPIO1 SDN GND Pin Assignments GPIO0 GPIO2 VDD GPIO3 Fast wake and hop times Power supply = 1.8 to 3.8 V Excellent selectivity performance 69 dB adjacent channel 79 dB blocking at 1 MHz Antenna diversity and T/R switch control Highly configurable packet handler TX and RX 64 byte FIFOs 129 bytes dedicated Tx or Rx FIFO Auto frequency control (AFC) Automatic gain control (AGC) Low BOM Low battery detector Temperature sensor 20-Pin QFN package Sub-GHz 802.15.4 mesh network ready IEEE 802.15.4g, and WMBus compliant Suitable for FCC Part 90 Mask D, FCC part 15.247, 15,231, 15,249, ARIB T-108, T-96, T-67, RCR STD-30, China regulatory ETSI Category I Operation EN 300 220 TXRamp Frequency range = 142-1050 MHz Receive sensitivity = -133 dBm @ 100 bps plus fast-scanning AFC for standard TCXO applications Modulation (G)FSK, 4(G)FSK, (G)MSK OOK Max output power +20 dBm (Si4468) +13 dBm (Si4467) PA support for +27 or +30 dBm Low active power consumption 10/13 mA RX 18 mA TX at +10 dBm (Si4467) Ultra low current powerdown modes 30 nA shutdown, 40 nA standby Preamble sense mode 6 mA average RX current at 1.2 kbps 10 A average RX current at 50 kbps and 1 sec sleep interval Fast preamble detection 1 byte preamble detection Data rate = 100 bps to 1 Mbps VDD 11 nIRQ Patents pending Silicon Laboratories' Si446x devices are high-performance, low-current transceivers covering the sub-GHz frequency bands from 142 to 1050 MHz. The radios are part of the EZRadioPRO(R) family, which includes a complete line of transmitters, receivers, and transceivers covering a wide range of applications. A high level of integration including support for IEEE 802.15.4 features enables standards based sub GHz networking solutions. All parts offer outstanding sensitivity of -133 dBm while achieving extremely low active and standby current consumption. The Si4468/7 offers frequency coverage in all major bands. The Si446x includes optimal phase noise, blocking, and selectivity performance for narrow band and licensed band applications, such as FCC Part90 and 169 MHz wireless MBus. The 69 dB adjacent channel selectivity with 12.5 kHz channel spacing ensures robust receive operation in harsh RF conditions, which is particularly important for narrow band operation. The Si4468 offers exceptional output power of up to +20 dBm with outstanding TX efficiency. The high output power and sensitivity results in an industry-leading link budget of 155 dB allowing extended ranges and highly robust communication links. The Si4467 active mode TX current consumption of 18 mA at +10 dBm and RX current of 10 mA coupled with extremely low standby current and fast wake times ensure extended battery life in the most demanding applications. The Si4468 can achieve up to +27 dBm output power with built-in ramping control of a low-cost external FET. The devices can meet worldwide regulatory standards: FCC, ETSI, and ARIB. All devices are designed to be compliant with 802.15.4g and WMBus smart metering standards. The devices are highly flexible and can be configured via the Wireless Development Suite (WDS) available at www.silabs.com. Rev 1.0 10/14 Copyright (c) 2014 by Silicon Laboratories Si4468/7 Si4468/7 Functional Block Diagram GPIO3 GPIO2 XIN XOUT Loop Filter PFD / CP VCO FBDIV TX DIV SDN RXN TX LO Gen Bootup OSC IF PKDET RF PKDET LNA PGA PA ADC MODEM FIFO Packet Handler nSEL SDI SDO SCLK nIRQ LDOs PowerRamp Cntl POR LBD 32K LP OSC PA LDO TXRAMP 2 30 MHz XO SPI Interface Controller RXP Frac-N Div VDD Digital Logic GPIO0 GPIO1 Product Freq. Range Max Output Power Ultra Narrow Band Support IEEE 802.15.4 / 4g Ready Si4468 Major bands 142-1050 MHz +20 dBm Si4467 Major bands 142-1050 MHz +13 dBm Rev 1.0 Si4468/7 TABLE O F C ONTENTS Section Page 1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 2.1. Boot Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 3. Controller Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 3.1. Serial Peripheral Interface (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 3.2. Fast Response Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 3.3. Operating Modes and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 3.4. Application Programming Interface (API) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 3.5. Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 3.6. GPIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 4. Modulation and Hardware Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 4.1. Modulation Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 4.2. Hardware Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 4.3. Preamble Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 5. Internal Functional Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 5.1. RX Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 5.2. RX Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 5.3. Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 5.4. Transmitter (TX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 5.5. Crystal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 6. Data Handling and Packet Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 6.1. RX and TX FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 6.2. Packet Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 7. RX Modem Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 8. Auxiliary Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 8.1. Wake-up Timer and 32 kHz Clock Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 8.2. Low Duty Cycle Mode (Auto RX Wake-Up) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 8.3. Temperature, Battery Voltage, and Auxiliary ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 8.4. Low Battery Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 8.5. Antenna Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 8.6. Preamble Sense Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 9. Standards Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 9.1. Wireless MBus Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 9.2. ETSI EN300 220 Category 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 9.3. IEEE 802.15.4 Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 10. Packet Trace Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 11. Pin Descriptions: Si4468/7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 12. Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 13. Package Outline: Si4468/7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 14. PCB Land Pattern: Si4468/7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53 15. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 15.1. Si4468/7 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 15.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 Rev 1.0 3 Si4468/7 1. Electrical Specifications Table 1. DC Characteristics1 Parameter Supply Voltage Range Symbol Min Typ Max Unit 1.8 3.3 3.8 V RC Oscillator, Main Digital Regulator, and Low Power Digital Regulator OFF -- 30 1300 nA IStandby Register values maintained and RC oscillator/WUT OFF -- 40 2900 nA ISleepRC RC Oscillator/WUT ON and all register values maintained, and all other blocks OFF -- 740 3800 nA ISleepXO Sleep current using an external 32 kHz crystal -- 1.7 -- A ISensor Low battery detector ON, register values maintained, and all other blocks OFF -- 1 -- A IReady Crystal Oscillator and Main Digital Regulator ON, all other blocks OFF -- 1.8 -- mA Ipsm Duty cycling during preamble search, 1.2 kbps, 4 byte preamble (no sensitivity degradation) -- 6 -- mA Ipsm Fixed 1 s wakeup interval, 50 kbps, 5 byte preamble -- 10 -- A ITune_RX RX Tune, High Performance Mode -- 7.6 -- mA ITune_TX TX Tune, High Performance Mode -- 7.8 -- mA IRXH High Performance Mode Measured at 915 MHz and 40 kbps data rate. -- 13.7 22 mA IRXL Low Power Mode Measured at 315 MHz and 40 kbps data -- 10.9 -- mA ITX_+20 +20 dBm output power, Class-E match, 915 MHz, 3.3 V -- 88 108 mA +20 dBm output power, square-wave match, 169 MHz, 3.3 V -- 68.5 80 mA +13 dBm output power, Class-E match, 915 MHz, 3.3 V -- 44.5 60 mA ITX_+10 +10 dBm output power, Class-E match, 915/868 MHz, 3.3 V2 -- 19.7 -- mA ITX_+10 +10 dBm output power, Class-E match, 169 MHz, 3.3 V2 -- 18 -- mA ITX_+13 +13 dBm output power, Class-E match, 915/868 MHz, 3.3 V -- 24 -- mA VDD Power Saving Modes IShutdown -LBD Preamble Sense Mode Current TUNE Mode Current RX Mode Current TX Mode Current (Si4468) TX Mode Current (Si4467) Test Condition Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. 2. Measured on direct tie RF evaluation board. 4 Rev 1.0 Si4468/7 Table 2. Synthesizer AC Electrical Characteristics Parameter Synthesizer Frequency Range Synthesizer Frequency Resolution Symbol Test Condition FSYN Min Typ Max Unit 850 -- 1050 MHz 350 -- 525 MHz 284 -- 350 MHz 142 -- 175 MHz FRES-960 850-1050 MHz -- 28.6 -- Hz FRES-525 420-525 MHz -- 14.3 -- Hz FRES-420 350-420 MHz -- 11.4 -- Hz FRES-350 283-350 MHz -- 9.5 -- Hz FRES-175 142-175 MHz -- 4.7 -- Hz Synthesizer Settling Time tLOCK Measured from exiting Ready mode with XOSC running to any frequency. Including VCO Calibration. -- 50 -- s Phase Noise L(fM) F = 10 kHz, 169 MHz, High Perf Mode -- -117 -108 dBc/Hz F = 100 kHz, 169 MHz, High Perf Mode -- -120 -115 dBc/Hz F = 1 MHz, 169 MHz, High Perf Mode -- -138 -135 dBc/Hz F = 10 MHz, 169 MHz, High Perf Mode -- -148 -143 dBc/Hz F = 10 kHz, 915 MHz, High Perf Mode -- -102 -94 dBc/Hz F = 100 kHz, 915 MHz, High Perf Mode -- -105 -97 dBc/Hz F = 1 MHz, 915 MHz, High Perf Mode -- -125 -122 dBc/Hz F = 10 MHz, 915 MHz, High Perf Mode -- -138 -135 dBc/Hz Note: All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. Rev 1.0 5 Si4468/7 Table 3. Receiver AC Electrical Characteristics1,2 Parameter RX Frequency Range RX Sensitivity 169 MHz3 Symbol Test Condition FRX Min Typ Max Unit 850 -- 1050 MHz 350 -- 525 MHz 284 -- 350 MHz 142 -- 175 MHz PRX_0.1 (BER < 0.1%) (100 bps, GFSK, BT = 0.5, f = 100 Hz) -- -133 -- dBm PRX_40 (BER < 0.1%) (40 kbps, GFSK, BT = 0.5, f = 20 kHz) -- -110 -108 dBm PRX_100 (BER < 0.1%) (100 kbps, GFSK, BT = 0.5, f = 50 kHz) -- -106 -104 dBm PRX_500 (BER < 0.1%) (500 kbps, GFSK, BT = 0.5, f = 250 kHz) -- -98 -96 dBm PRX_9.6 (PER 1%) (9.6 kbps, 4GFSK, BT = 0.5, f = 2.4 kHz) -- -110 -- dBm PRX_1M (PER 1%) (1 Mbps, 4GFSK, BT = 0.5, inner deviation = 83.3 kHz) -- -89 -- dBm PRX_OOK (BER < 0.1%, 4.8 kbps, 350 kHz BW, OOK, PN15 data) -- -110 -107 dBm (BER < 0.1%, 40 kbps, 350 kHz BW, OOK, PN15 data) -- -103 -100 dBm (BER < 0.1%, 120 kbps, 350 kHz BW, OOK, PN15 data) -- -97 -93 dBm Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. 2. For PER tests, 48 preamble symbols, 4 byte sync word, 10 byte payload and CRC-32 was used. 3. Measured over 50000 bits using PN9 data sequence and data and clock on GPIOs. Sensitivity is expected to be better if reading data from packet handler FIFO especially at higher data rates. 4. Conducted emissions measured on RF evaluation boards. 6 Rev 1.0 Si4468/7 Table 3. Receiver AC Electrical Characteristics1,2 (Continued) Parameter RX Sensitivity 915/868 MHz3 RX Channel Bandwidth RSSI Resolution Symbol Test Condition Min Typ Max Unit PRX_0.1 (BER < 0.1%) (100 bps, GFSK, BT = 0.5, f = 100 Hz) -- -132 -- dBm PRX_40 (BER < 0.1%) (40 kbps, GFSK, BT = 0.5, f = 20 kHz) -- -109 -107 dBm PRX_100 (BER < 0.1%) (100 kbps, GFSK, BT = 0.5, f = 50 kHz) -- -104 -102 dBm PRX_500 (BER < 0.1%) (500 kbps, GFSK, BT = 0.5, f = 250 kHz) -- -97 -92 dBm PRX_9.6 (PER 1%) (9.6 kbps, 4GFSK, BT = 0.5, f = kHz) -- -109 -- dBm PRX_1M (PER 1%) (1 Mbps, 4GFSK, BT = 0.5, inner deviation = 83.3 kHz) -- -88 -- dBm PRX_OOK (BER < 0.1%, 4.8 kbps, 350 kHz BW, OOK, PN15 data) -- -108 -104 dBm (BER < 0.1%, 40 kbps, 350 kHz BW, OOK, PN15 data) -- -101 -97 dBm (BER < 0.1%, 120 kbps, 350 kHz BW, OOK, PN15 data) -- -96 -91 dBm 0.2 -- 850 kHz -- 0.5 -- dB BW RESRSSI Valid from -110 dBm to -90 dBm 1-Ch Offset Selectivity, 169 MHz3 C/I1-CH -69 -59 dB 1-Ch Offset Selectivity, 450 MHz3 C/I1-CH -60 -50 dB 1-Ch Offset Selectivity, 868 / 915 MHz3 C/I1-CH Desired Ref Signal 3 dB above sensitivity, BER < 0.1%. Interferer is CW, and desired is modulated with 2.4 kbps F = 1.2 kHz GFSK with BT = 0.5, RX channel BW = 4.8 kHz, channel spacing = 12.5 kHz -55 -45 dB Desired Ref Signal 3 dB above sensitivity, BER = 0.1%. Interferer is CW, and desired is modulated with 2.4 kbps, F = 1.2 kHz GFSK with BT = 0.5, RX channel BW = 4.8 kHz -79 -68 dB -86 -75 dB Blocking 1 MHz Offset 1MBLOCK Blocking 8 MHz Offset 8MBLOCK Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. 2. For PER tests, 48 preamble symbols, 4 byte sync word, 10 byte payload and CRC-32 was used. 3. Measured over 50000 bits using PN9 data sequence and data and clock on GPIOs. Sensitivity is expected to be better if reading data from packet handler FIFO especially at higher data rates. 4. Conducted emissions measured on RF evaluation boards. Rev 1.0 7 Si4468/7 Table 3. Receiver AC Electrical Characteristics1,2 (Continued) Parameter Image Rejection (IF = 468.75 kHz) Symbol Test Condition Min Typ Max Unit ImREJ No image rejection calibration. Rejection at the image frequency. RF = 460 MHz 30 40 -- dB With image rejection calibration in Si446x. Rejection at the image frequency. RF = 460 MHz 40 55 -- dB No image rejection calibration. Rejection at the image frequency. RF = 915 MHz 30 45 -- dB With image rejection calibration in Si446x. Rejection at the image frequency. RF = 915 MHz 40 52 -- dB No image rejection calibration. Rejection at the image frequency. RF = 169 MHz 35 45 -- dB With image rejection calibration in Si446x. Rejection at the image frequency. RF = 169 MHz 45 60 -- dB Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. 2. For PER tests, 48 preamble symbols, 4 byte sync word, 10 byte payload and CRC-32 was used. 3. Measured over 50000 bits using PN9 data sequence and data and clock on GPIOs. Sensitivity is expected to be better if reading data from packet handler FIFO especially at higher data rates. 4. Conducted emissions measured on RF evaluation boards. 8 Rev 1.0 Si4468/7 Table 4. Transmitter AC Electrical Characteristics Parameter TX Frequency Range Symbol Test Condition FTX Min Typ Max Unit 850 -- 1050 MHz 350 -- 525 MHz 284 -- 350 MHz 142 -- 175 MHz (G)FSK Data Rate DRFSK 0.1 -- 500 kbps 4(G)FSK Data Rate DR4FSK 0.2 -- 1000 kbps OOK Data Rate DROOK 0.1 -- 120 kbps Modulation Deviation Range f960 850-1050 MHz -- 1.5 -- MHz f525 420-525 MHz -- 750 -- kHz f420 350-420 MHz -- 600 -- kHz f350 283-350 MHz -- 500 -- kHz f175 142-175 MHz -- 250 -- kHz FRES-960 850-1050 MHz -- 28.6 -- Hz FRES-525 420-525 MHz -- 14.3 -- Hz FRES-420 350-420 MHz -- 11.4 -- Hz FRES-350 283-350 MHz -- 9.5 -- Hz FRES-175 142-175 MHz -- 4.7 -- Hz Output Power Range (Si4468) PTX68 Typical range at 3.3 V -20 -- +20 dBm Output Power Range (Si4467) PTX67 Typical range at 3.3 V with Class E match optimized for best PA efficiency -20 -- +12.5 dBm Output Power Variation (Si4468) At 20 dBm PA power setting, 915 MHz, Class E match, 3.3 V, 25 C 19 20 21 dBm Output Power Variation (Si4467) At 10 dBm PA power setting, 915 MHz, Class E match, 3.3 V, 25 C 9 10 11 dBm Modulation Deviation Resolution Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. 2. The maximum data rate is dependent on the XTAL frequency and is calculated as per the formula: Maximum Symbol Rate = Fxtal/60, where Fxtal is the XTAL frequency (typically 30 MHz). 3. Default API setting for modulation deviation resolution is double the typical value specified. 4. Output power is dependent on matching components and board layout. Rev 1.0 9 Si4468/7 Table 4. Transmitter AC Electrical Characteristics (Continued) Parameter Test Condition Min Typ Max Unit Output Power Variation (Si4468) At 20 dBm PA power setting, 169 MHz, Square Wave match, 3.3 V, 25 C 18.5 20 21 dBm Output Power Variation (Si4467) At 10 dBm PA power setting, 169 MHz, Class E match, 3.3 V, 25 C 9.5 10 10.5 dBm PRF_OUT Using switched current match within 6 dB of max power using CLE match within 6 dB of max power -- 0.25 0.4 dB TX RF Output Level Variation vs. Temperature PRF_TEMP -40 to +85 C -- 2.3 3 dB TX RF Output Level Variation vs. Frequency PRF_FREQ Measured across 902-928 MHz -- 0.6 1.7 dB BT Gaussian Filtering Bandwith Time Product -- 0.5 -- TX RF Output Steps Transmit Modulation Filtering Symbol Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. 2. The maximum data rate is dependent on the XTAL frequency and is calculated as per the formula: Maximum Symbol Rate = Fxtal/60, where Fxtal is the XTAL frequency (typically 30 MHz). 3. Default API setting for modulation deviation resolution is double the typical value specified. 4. Output power is dependent on matching components and board layout. 10 Rev 1.0 Si4468/7 Table 5. Auxiliary Block Specifications1 Parameter Symbol Test Condition Min Typ Max Unit Temperature Sensor Sensitivity TSS -- 4.5 -- ADC Codes/ C Low Battery Detector Resolution LBDRES -- 50 -- mV Microcontroller Clock Output Frequency Range2 Temperature Sensor Conversion XTAL Range3 30 MHz XTAL Start-Up Time 30 MHz XTAL Cap Resolution 32 kHz XTAL Start-Up Time 32 kHz Accuracy using Internal RC Oscillator POR Reset Time FMC Configurable to Fxtal or Fxtal divided by 2, 3, 7.5, 10, 15, or 30 where Fxtal is the reference XTAL frequency. In addition, 32.768 kHz is also supported. 32.768K -- Fxtal Hz TEMPCT Programmable setting -- 3 -- ms 25 -- 32 MHz -- 300 -- s 30MRES -- 70 -- fF t32k -- 2 -- sec 32KRCRES -- 2500 -- ppm tPOR -- -- 6 ms XTALRange t30M Start-up time will vary with XTAL type and board layout. Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -45 to +85 C unless otherwise stated. All typical values apply at Vdd=3.3V and 25C unless otherwise stated. 2. Microcontroller clock frequency tested in production at 1 MHz, 30 MHz, 32 MHz, and 32.768 kHz. Other frequencies tested by bench characterization. 3. XTAL Range tested in production using an external clock source (similar to using a TCXO). Rev 1.0 11 Si4468/7 Table 6. Digital IO Specifications (GPIO_x, SCLK, SDO, SDI, nSEL, nIRQ, SDN)1 Parameter Rise Time 2,3 Fall Time3,4 Symbol Test Condition Min Typ Max Unit TRISE 0.1 x VDD to 0.9 x VDD, CL = 10 pF, DRV<1:0> = LL -- 2.3 -- ns TFALL 0.9 x VDD to 0.1 x VDD, CL = 10 pF, DRV<1:0> = LL -- 2 -- ns Input Capacitance CIN -- 2 -- pF Logic High Level Input Voltage VIH VDD x 0.7 -- -- V Logic Low Level Input Voltage VIL -- -- VDD x 0.3 V Input Current IIN 0<VIN< VDD -1 -- 1 A Input Current If Pullup is Activated IINP VIL = 0 V 1 -- 4 A LL3 -- 6.66 -- mA DRV[1:0] = LH 3 -- 5.03 -- mA IOmaxHL DRV[1:0] = HL 3 -- 3.16 -- mA IOmaxHH DRV[1:0] = HH3 -- 1.13 -- mA IOmaxLL 3 -- 5.75 -- mA 3 -- 4.37 -- mA IOmaxHL DRV[1:0] = HL3 -- 2.73 -- mA IOmaxHH DRV[1:0] = HH3 -- 0.96 -- mA IOmaxLL 3 -- 2.53 -- mA LH3 -- 2.21 -- mA IOmaxHL DRV[1:0] = HL 3 -- 1.70 -- mA IOmaxHH DRV[1:0] = HH3 -- 0.80 -- mA Logic High Level Output Voltage VOH DRV[1:0] = HL VDD x 0.8 -- -- V Logic Low Level Output Voltage VOL DRV[1:0] = HL -- -- VDD x 0.2 V Drive Strength for Output Low Level Drive Strength for Output High Level Drive Strength for Output High Level for GPIO0 IOmaxLL IOmaxLH IOmaxLH IOmaxLH DRV[1:0] = DRV[1:0] = LL DRV[1:0] = LH DRV[1:0] = LL DRV[1:0] = Notes: 1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and from -40 to +85 C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 C unless otherwise stated. 2. 6.7 ns is typical for GPIO0 rise time. 3. Assuming VDD = 3.3 V, drive strength is specified at Voh (min) = 2.64 V and Vol(max) = 0.66 V at room temperature. 4. 2.4 ns is typical for GPIO0 fall time. 12 Rev 1.0 Si4468/7 Table 7. Thermal Characteristics Parameter Symbol Value Unit Operating Ambient Temperature Range TA -40 to +125 C Thermal Impedance Junction to Ambient* JA 25 C/w Tj +137 C TSTG -55 to +150 C Value Unit VDD to GND -0.3, +3.8 V Instantaneous VRF-peak to GND on TX Output Pin -0.3, +8.0 V Sustained VRF-peak to GND on TX Output Pin -0.3, +6.5 V -0.7, VDD + 0.3 V +10 dBm Junction Temperature Maximum Value* Storage Temperature Range *Note: JA and Tj are based on RF evaluation board measurements. Table 8. Absolute Maximum Ratings Parameter Voltage on Analog Inputs RX Input Power Note: Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only and functional operation of the device at or beyond these ratings in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Power Amplifier may be damaged if switched on without proper load or termination connected. TX matching network design will influence TX VRF-peak on TX output pin. Caution: ESD sensitive device. Rev 1.0 13 Si4468/7 2. Functional Description The Si446x devices are high-performance, low-current, wireless ISM transceivers that cover the sub-GHz bands. A key feature of the Si4468/7 is the support for IEEE 802.15.4g PHY and some features of 802.15.4 above the physical layer, which enables low-power, long-range networking solutions including mesh networking. In conjunction with Silicon Labs industry-leading ZigBee SoCs and EFM32 energy-friendly 32-bit ARM based microcontrollers, the Si4468/7 enables low-power solutions from sub GHz to 2.4 GHz for various "Internet of Things" applications. The wide operating voltage range of 1.8-3.8 V and low current consumption make the Si446x an ideal solution for battery powered applications. The Si446x operates as a time division duplexing (TDD) transceiver where the device alternately transmits and receives data packets. The device uses a single-conversion mixer to downconvert the 2/4-level FSK/GFSK or OOK modulated receive signal to a low IF frequency. Following a programmable gain amplifier (PGA) the signal is converted to the digital domain by a high performance ADC allowing filtering, demodulation, slicing, and packet handling to be performed in the built-in DSP increasing the receiver's performance and flexibility versus analog based architectures. The demodulated signal is output to the system MCU through a programmable GPIO or via the standard SPI bus by reading the 64-byte RX FIFO. A single high precision local oscillator (LO) is used for both transmit and receive modes since the transmitter and receiver do not operate at the same time. The LO is generated by an integrated VCO and Fractional-N PLL synthesizer. The synthesizer is designed to support configurable data rates from 100 bps to 1 Mbps. The Si4468/7 operate in the frequency bands of 142-175, 283-350, 350-525, and 850-1050 MHz with a maximum frequency accuracy step size of 28.6 Hz. The transmit FSK data is modulated directly into the data stream and can be shaped by a Gaussian low-pass filter to reduce unwanted spectral content. The Si4468 contains a power amplifier (PA) that supports output power up to +20 dBm with very high efficiency, consuming only 70 mA at 169 MHz and 85 mA at 915 MHz. The integrated +20 dBm power amplifier can also be used to compensate for the reduced performance of a lower cost, lower performance antenna or antenna with size constraints due to a small form-factor. Competing solutions require large and expensive external PAs to achieve comparable performance. The Si4467 is designed to support single coin cell operation with current consumption below 18 mA for +10 dBm output power. Two match topologies are available for the Si4467: Class-E and switched-current. Class-E matching provides optimal current consumption, while switched-current matching demonstrates the best performance over varying battery voltage and temperature with slightly higher current consumption. The PA is single-ended to allow for easy antenna matching and low BOM cost. The PA incorporates automatic ramp-up and ramp-down control to reduce unwanted spectral spreading. The Si446x family supports frequency hopping, TX/RX switch control, and antenna diversity switch control to extend the link range and improve performance. Built-in antenna diversity and support for frequency hopping can be used to further extend range and enhance performance. Antenna diversity is completely integrated into the Si446x and can improve the system link budget by 8-10 dB, resulting in substantial range increases under adverse environmental conditions. A highly configurable packet handler allows for autonomous encoding/decoding of nearly any packet structure. Additional system features, such as an automatic wake-up timer, low battery detector, 64 byte TX/RX FIFOs, and preamble detection, reduce overall current consumption and allows for the use of lower-cost system MCUs. An integrated temperature sensor, power-on-reset (POR), and GPIOs further reduce overall system cost and size. The Si446x is designed to work with an MCU, crystal, and a few passive components to create a very low-cost system. 2.1. Boot Modes The Si4468/7 has two boot modes. One boot mode supports 802.15.4 functionality to enable standards-based, sub-GHz mesh networking with support for 802.15.4 MR-FSK PHY (15.4g) and key MAC (15.4) features. The second boot mode supports legacy Si4463/1/0 compatibility and is intended to support proprietary solutions that require additional flexibility in configuring the device. The legacy boot mode is called EZRadioPRO boot mode. This mode is software- and hardware-compatible with Si4463/1/0 and also supports 802.15.4g PHY and WMBus operation. The boot mode selection is done using the POWER_UP command and is described in the API documentation. The application shown in Figure 1 is designed for a system with a TX/RX direct-tie configuration without the use of a TX/RX switch. Figure 2 demonstrates an application for +20 dBm using an external T/R-switch. 14 Rev 1.0 Si4468/7 TX L2 C4 C3 XOUT XIN GND 2 14 Si4467 3 5 L1 nSEL 13 12 4 NC C2 17 6 7 11 10 9 8 SDI GP1 GP2 SDO GP3 SCLK GP4 nIRQ GP5 GPIO1 L3 18 GPIO0 L4 RXn C1 16 15 VDD C5 RXp L5 19 VDD C7 20 1 Microcontroller SDN GPIO2 C8 TXRAMP C6 GPIO3 30 MHz VDD Figure 1. Si4467 Direct-Tie Application Example C4 TX NC C1 C3 C2 L1 XIN GND XOUT 16 15 2 14 Si4468 3 13 12 4 5 6 7 8 9 11 10 nSEL SDI GP1 GP2 SDO GP3 SCLK GP4 nIRQ GP5 Microcontroller C5 L2 17 GPIO1 L3 RXn 18 GPIO0 L4 L5 19 VDD C6 RXp 20 1 TXRAMP SDN VDD C7 GPIO2 GPIO3 30 MHz VDD Figure 2. Si4468 Single Antenna with RF Switch Example Rev 1.0 15 Si4468/7 3. Controller Interface 3.1. Serial Peripheral Interface (SPI) The Si446x communicates with the host MCU over a standard 4-wire serial peripheral interface (SPI): SCLK, SDI, SDO, and nSEL. The SPI interface is designed to operate at a maximum of 10 MHz. The SPI timing parameters are demonstrated in Table 9. The host MCU writes data over the SDI pin and can read data from the device on the SDO output pin. Figure 3 demonstrates an SPI write command. The nSEL pin should go low to initiate the SPI command. The first byte of SDI data will be one of the firmware commands followed by n bytes of parameter data which will be variable depending on the specific command. The rising edges of SCLK should be aligned with the center of the SDI data. Table 9. Serial Interface Timing Parameters Symbol Parameter Min (ns) Max (ns) tCH Clock high time 40 tCL Clock low time 40 tDS Data setup time 20 tDH Data hold time 20 tDD Output data delay time 43 tDE Output disable time 45 tSS Select setup time 20 tSH Select hold time 50 tSW Select high period 80 Diagram SCLK tSS tCL tCH tDS tDH tDD tSH tDE SDI SDO tSW nSEL *Note: CL = 10 pF; VDD = 1.8 V; SDO Drive strength setting = 10. nSEL SDO SDI FW Command Param Byte 0 Param Byte n SCLK Figure 3. SPI Write Command The Si446x contains an internal MCU which controls all the internal functions of the radio. For SPI read commands a typical MCU flow of checking clear-to-send (CTS) is used to make sure the internal MCU has executed the command and prepared the data to be output over the SDO pin. Figure 4 demonstrates the general flow of an SPI read command. Once the CTS value reads FFh then the read data is ready to be clocked out to the host MCU. The typical time for a valid FFh CTS reading is 20 s. Figure 5 demonstrates the remaining read cycle after CTS is set to FFh. The internal MCU will clock out the SDO data on the negative edge so the host MCU should process the SDO data on the rising edge of SCLK. 16 Rev 1.0 Si4468/7 Firmware Flow 0xFF Send Command Read CTS CTS Value Retrieve Response 0x00 NSEL CTS SDO SDI ReadCmdBuff SCK Figure 4. SPI Read Command--Check CTS Value NSEL SDO Response Byte 0 Response Byte n SDI SCK Figure 5. SPI Read Command--Clock Out Read Data Rev 1.0 17 Si4468/7 3.2. Fast Response Registers The fast response registers are registers that can be read immediately without the requirement to monitor and check CTS. There are four fast response registers that can be programmed for a specific function. The fast response registers can be read through API commands, 0x50 for Fast Response A, 0x51 for Fast Response B, 0x53 for Fast Response C, and 0x57 for Fast Response D. The fast response registers can be configured by the "FRR_CTL_X_MODE" properties. The fast response registers may be read in a burst fashion. After the initial 16 clock cycles, each additional eight clock cycles will clock out the contents of the next fast response register in a circular fashion. The value of the FRRs will not be updated unless NSEL is toggled. 3.3. Operating Modes and Timing The primary states of the Si446x are shown in Figure 6. The shutdown state completely shuts down the radio to minimize current consumption. Standby/Sleep, SPI Active, Ready, TX Tune, and RX tune are available to optimize the current consumption and response time to RX/TX for a given application. API commands START_RX, START_TX, and CHANGE_STATE control the operating state with the exception of shutdown which is controlled by SDN, pin 1. Table 10 shows each of the operating modes with the time required to reach either RX or TX mode as well as the current consumption of each mode. The times in Table 9 are measured from the rising edge of nSEL until the chip is in the desired state. Note that these times are indicative of state transition timing but are not guaranteed and should only be used as a reference data point. An automatic sequencer will put the chip into RX or TX from any state. It is not necessary to manually step through the states. To simplify the diagram it is not shown but any of the lower power states can be returned to automatically after RX or TX. Figure 6. State Machine Diagram 18 Rev 1.0 Si4468/7 Table 10. Operating State Response Time and Current Consumption Response Time to TX RX Current in State /Mode Shutdown State 15 ms 15 ms 30 nA Standby State Sleep State SPI Active State Ready State TX Tune State RX Tune State 440 s 440 s 340 s 100 s 58 s -- 440 s 440 s 340 s 100 s -- 60 s 40 nA 740 nA 1.35 mA 1.8 mA 7.8 mA 7.6 mA TX State -- 100 s 18 mA @ +10 dBm RX State 100 s 75 s 10.9 or 13.7 mA State/Mode Note: TXRX and RXTX state transition timing can be reduced to 70 s if using Zero-IF mode. Figure 7 shows the POR timing and voltage requirements. The power consumption (battery life) depends on the duty cycle of the application or how often the part is in either Rx or Tx state. In most applications the utilization of the standby state will be most advantageous for battery life but for very low duty cycle applications shutdown will have an advantage. For the fastest timing the next state can be selected in the START_RX or START_TX API commands to minimize SPI transactions and internal MCU processing. 3.3.1. Power on Reset (POR) A Power On Reset (POR) sequence is used to boot the device up from a fully off or shutdown state. To execute this process, VDD must ramp within 1ms and must remain applied to the device for at least 10 ms. If VDD is removed, then it must stay below 0.15 V for at least 10 ms before being applied again. See Figure 7 and Table 11 for details. VDD VR RH VR RL Time tSR tPORH Figure 7. POR Timing Diagram Rev 1.0 19 Si4468/7 Table 11. POR Timing Variable tPORH Description High time for VDD to fully settle POR circuit tPORL Low time for VDD to enable POR VRRH Voltage for successful POR VRRL Starting Voltage for successful POR tSR Min Typ Max Units 10 ms 10 ms 90% x Vdd V 0 Slew rate of VDD for successful POR 150 mV 1 ms 3.3.2. Shutdown State The shutdown state is the lowest current consumption state of the device with nominally less than 30 nA of current consumption. The shutdown state may be entered by driving the SDN pin (Pin 1) high. The SDN pin should be held low in all states except the shutdown state. In the shutdown state, the contents of the registers are lost and there is no SPI access. When coming out of the shutdown state a power on reset (POR) will be initiated along with the internal calibrations. After the POR the POWER_UP command is required to initialize the radio. The SDN pin needs to be held high for at least 10us before driving low again so that internal capacitors can discharge. Not holding the SDN high for this period of time may cause the POR to be missed and the device to boot up incorrectly. If POR timing and voltage requirements cannot be met, it is highly recommended that SDN be controlled using the host processor rather than tying it to GND on the board. 3.3.3. Standby State Standby state has the lowest current consumption with the exception of shutdown but has much faster response time to RX or TX mode. In most cases standby should be used as the low power state. In this state the register values are maintained with all other blocks disabled. The SPI is accessible during this mode but any SPI event, including FIFO R/W, will enable an internal boot oscillator and automatically move the part to SPI active state. After an SPI event the host will need to re-command the device back to standby through the "Change State" API command to achieve the 40 nA current consumption. If an interrupt has occurred (i.e., the nIRQ pin = 0) the interrupt registers must be read to achieve the minimum current consumption of this mode. 3.3.4. Sleep State Sleep state is the same as standby state but the wake-up-timer and a 32 kHz clock source are enabled. The source of the 32 kHz clock can either be an internal 32 kHz RC oscillator which is periodically calibrated or a 32 kHz oscillator using an external XTAL.The SPI is accessible during this mode but an SPI event will enable an internal boot oscillator and automatically move the part to SPI active mode. After an SPI event the host will need to re-command the device back to sleep. If an interrupt has occurred (i.e., the nIRQ pin = 0) the interrupt registers must be read to achieve the minimum current consumption of this mode. 3.3.5. SPI Active State In SPI active state the SPI and a boot up oscillator are enabled. After SPI transactions during either standby or sleep the device will not automatically return to these states. A "Change State" API command will be required to return to either the standby or sleep modes. 3.3.6. Ready State Ready state is designed to give a fast transition time to TX or RX state with reasonable current consumption. In this mode the Crystal oscillator remains enabled reducing the time required to switch to TX or RX mode by eliminating the crystal start-up time. 3.3.7. TX State The TX state may be entered from any of the state with the "Start TX" or "Change State" API commands. A built-in sequencer takes care of all the actions required to transition between states from enabling the crystal oscillator to ramping up the PA. The following sequence of events will occur automatically when going from standby to TX state. 1. Enable internal LDOs. 2. Start up crystal oscillator and wait until ready (controlled by an internal timer). 20 Rev 1.0 Si4468/7 3. Enable PLL. 4. Calibrate VCO/PLL. 5. Wait until PLL settles to required transmit frequency (controlled by an internal timer). 6. Activate power amplifier and wait until power ramping is completed (controlled by an internal timer). 7. Transmit packet. Steps in this sequence may be eliminated depending on which state the chip is configured to prior to commanding to TX. By default, the VCO and PLL are calibrated every time the PLL is enabled. When the START_TX API command is utilized the next state may be defined to ensure optimal timing and turnaround. Figure 8 shows an example of the commands and timing for the START_TX command. CTS will go high as soon as the sequencer puts the part into TX state. As the sequencer is stepping through the events listed above, CTS will be low and no new commands or property changes are allowed. If the Fast Response (FRR) or nIRQ is used to monitor the current state there will be slight delay caused by the internal hardware from when the event actually occurs to when the transition occurs on the FRR or nIRQ. The time from entering TX state to when the FRR will update is 5 s and the time to when the nIRQ will transition is 13 s. If a GPIO is programmed for TX state or used as control for a transmit/receive switch (TR switch) there is no delay. CTS NSEL SDI START_TX Current State FRR YYY State Tx State YYY State TXCOMPLETE_STATE Tx State TXCOMPLETE_STATE nIRQ GPIOx - TX state Figure 8. Start_TX Commands and Timing 3.3.8. RX State The RX state may be entered from any of the other states by using the "Start RX" or "Change State" API command. A built-in sequencer takes care of all the actions required to transition between states. The following sequence of events will occur automatically to get the chip into RX mode when going from standby to RX state: 1. Enable the digital LDO and the analog LDOs. 2. Start up crystal oscillator and wait until ready (controlled by an internal timer). 3. Enable PLL. 4. Calibrate VCO 5. Wait until PLL settles to required receive frequency (controlled by an internal timer). 6. Enable receiver circuits: LNA, mixers, and ADC. 7. Enable receive mode in the digital modem. Depending on the configuration of the radio, all or some of the following functions will be performed automatically by the digital modem: AGC, AFC (optional), update status registers, bit synchronization, packet handling (optional) including sync word, header check, and CRC. Similar to the TX state, the next state after RX may be defined in the "Start RX" API command. The START_RX commands and timing will be equivalent to the timing shown in Figure 8. Rev 1.0 21 Si4468/7 3.4. Application Programming Interface (API) An application programming interface (API), which the host MCU will communicate with, is embedded inside the device. The API is divided into two sections, commands and properties. The commands are used to control the chip and retrieve its status. The properties are general configurations which will change infrequently. The API descriptions can be found at www.silabs.com. 3.5. Interrupts The Si446x is capable of generating an interrupt signal when certain events occur. The chip notifies the microcontroller that an interrupt event has occurred by setting the nIRQ output pin LOW = 0. This interrupt signal will be generated when any one (or more) of the interrupt events (corresponding to the Interrupt Status bits) occur. The nIRQ pin will remain low until the host clears all interrupts. The nIRQ output signal will then be reset until the next change in status is detected. The interrupts sources are grouped into three groups: packet handler, chip status, and modem. The individual interrupts in these groups can be enabled/disabled in the interrupt property registers. An interrupt must be enabled for it to trigger an event on the nIRQ pin. The interrupt group must be enabled as well as the individual interrupts in API properties described in the API documentation. Once an interrupt event occurs and the nIRQ pin is low there are two ways to read and clear the interrupts. All of the interrupts may be read and cleared in the "GET_INT_STATUS" API command. By default all interrupts will be cleared once read. If only specific interrupts want to be read in the fastest possible method the individual interrupt groups (Packet Handler, Chip Status, Modem) may be read and cleared by the "GET_MODEM_STATUS", "GET_PH_STATUS" (packet handler), and "GET_CHIP_STATUS" API commands. The instantaneous status of a specific function maybe read if the specific interrupt is enabled or disabled. The status results are provided after the interrupts and can be read with the same commands as the interrupts. The status bits will give the current state of the function whether the interrupt is enabled or not. The fast response registers can also give information about the interrupt groups but reading the fast response registers will not clear the interrupt and reset the nIRQ pin. 22 Rev 1.0 Si4468/7 3.6. GPIO Four general purpose IO pins are available to utilize in the application. The GPIO are configured by the GPIO_PIN_CFG command in address 13h. For a complete list of the GPIO options please see the API guide. GPIO pins 0 and 1 should be used for active signals such as data or clock. GPIO pins 2 and 3 have more susceptibility to generating spurious in the synthesizer than pins 0 and 1. The drive strength of the GPIOs can be adjusted with the GEN_CONFIG parameter in the GPIO_PIN_CFG command. By default the drive strength is set to minimum. The default configuration for the GPIOs and the state during SDN is shown below in Table 12.The state of the IO during shutdown is also shown inTable 12. As indicated previously in Table 6, GPIO 0 has lower drive strength than the other GPIOs. Table 12. GPIOs Pin SDN State POR Default GPIO0 0 POR GPIO1 0 CTS GPIO2 0 POR GPIO3 0 POR nIRQ resistive VDD pull-up nIRQ SDO resistive VDD pull-up SDO SDI High Z SDI SCLK High Z SCLK NSEL High Z NSEL Rev 1.0 23 Si4468/7 4. Modulation and Hardware Configuration Options The Si446x supports different modulation options and can be used in various configurations to tailor the device to any specific application or legacy system for drop in replacement. The modulation and configuration options are set in API property, MODEM_MOD_TYPE. Refer to the API documentation for details on modem related properties. 4.1. Modulation Types The Si446x supports five different modulation options: Gaussian frequency shift keying (GFSK), frequency-shift keying (FSK), four-level GFSK (4GFSK), four-level FSK (4FSK), and on-off keying (OOK). Minimum shift keying (MSK) can also be created by using GFSK with the appropriate modulation index (h = 0.5). GFSK is the recommended modulation type as it provides the best performance and cleanest modulation spectrum. The modulation type is set by the "MOD_TYPE[2:0]" field in the "MODEM_MOD_TYPE" API property. A continuous-wave (CW) carrier may also be selected for RF evaluation purposes. The modulation source may also be selected to be a pseudo-random source for evaluation purposes. 4.2. Hardware Configuration Options There are different receive demodulator options to optimize the performance and mutually-exclusive options for how the RX/TX data is transferred from the host MCU to the RF device. 4.2.1. Receive Demodulator Options There are multiple demodulators integrated into the device to optimize the performance for different applications, modulation formats, and packet structures. The calculator built into WDS will choose the optimal demodulator based on the input criteria. 4.2.1.1. Synchronous Demodulator The synchronous demodulator's internal frequency error estimator acquires the frequency error based on a 101010 preamble structure. The bit clock recovery circuit locks to the incoming data stream within four transactions of a "10" or "01" bit stream. The synchronous demodulator gives optimal performance for 2- or 4-level (G)FSK modulation that has a modulation index less than 2. 4.2.1.2. Asynchronous Demodulator The asynchronous demodulator should be used for OOK modulation and for (G)FSK modulation under one or more of the following conditions: Modulation index > 2 preamble (not 1010101... pattern) When the modulation index exceeds 2, the asynchronous demodulator has better sensitivity compared to the synchronous demodulator. An internal deglitch circuit provides a glitch-free data output and a data clock signal to simplify the interface to the host. There is no requirement to perform deglitching in the host MCU. The asynchronous demodulator will typically be utilized for legacy systems and will have many performance benefits over devices used in legacy designs. Unlike the Si4432/31 solution for non-standard packet structures, there is no requirement to perform deglitching on the data in the host MCU. Glitch-free data is output from Si446x devices, and a sample clock for the asynchronous data can also be supplied to the host MCU; so, oversampling or bit clock recovery is not required by the host MCU. There are multiple detector options in the asynchronous demodulator block, which will be selected based upon the options entered into the WDS calculator. The asynchronous demodulator's internal frequency error estimator is able to acquire the frequency error based on any preamble structure. Non-standard 4.2.2. RX/TX Data Interface With MCU There are two different options for transferring the data from the RF device to the host MCU. FIFO mode uses the SPI interface to transfer the data, while direct mode transfers the data in real time over a GPIO pin. 4.2.2.1. FIFO Mode In FIFO mode, the transmit and receive data is stored in integrated FIFO register memory. The TX FIFO is accessed by writing command 66h followed directly by the data/clk that the host wants to write into the TX FIFO. The RX FIFO is accessed by writing command 77h followed by the number of clock cycles of data the host would like to read out of the RX FIFO. The RX data will be clocked out onto the SDO pin. 24 Rev 1.0 Si4468/7 In TX FIFO mode, the data bytes stored in FIFO memory are "packaged" together with other fields and bytes of information to construct the final transmit packet structure. These other potential fields include the Preamble, Sync word, and CRC checksum. In TX mode, the packet structure may be highly customized by enabling or disabling individual fields; for example, it is possible to disable both the Preamble and Sync Word fields and to load the entire packet structure into FIFO memory. For further information on the configuration of the FIFOs for a specific application or packet size, see "6. Data Handling and Packet Handler" on page 38. In RX mode, the Packet Handler must be enabled to allow storage of received data bytes into RX FIFO memory. The Packet Handler is required to detect the Sync Word, and proper detection of the Sync Word is required to determine the start of the Payload. All bytes after the Sync Word are stored in RX FIFO memory except the CRC checksum and (optionally) the variable packet length byte(s). When the FIFO is being used in RX mode, all of the received data may still be observed directly (in realtime) by properly programming a GPIO pin as the RXDATA output pin; this can be quite useful during application development. When in FIFO mode, the chip will automatically exit the TX or RX State when either the PACKET_SENT or PACKET_RX interrupt occurs. The chip will return to the state programmed in the argument of the "START TX" or "START RX" API command, TXCOMPLETE_STATE[3:0] or RXVALID_STATE[3:0]. For example, the chip may be placed into READY mode after a TX packet by sending the "START TX" command and by writing 30h to the TXCOMPLETE_STATE[3:0] argument. The chip will transmit all of the contents of the FIFO, and the PACKET_SENT interrupt will occur. When this event occurs, the chip will return to the READY state as defined by TXCOMPLETE_STATE[3:0] = 30h. 4.2.2.2. FIFO Direct Mode (Infinite Receive) In some applications, there is a need to receive extremely long packets (greater than 40 kB) while relying on preamble and sync word detection from the on-chip packet handler. In these cases, the packet length is unknown, and the device will load the bits after the sync word into the RX FIFO forever. Other features, such as Data Whitening, CRC, Manchester, etc., are supported in this mode, but CRC calculation is not because the end of packet is unknown to the device. The RX data and clock are also available on GPIO pins. The host MCU will need to reset the packet handler by issuing a START_RX to begin searching for a new packet. 4.2.2.3. Automatic TX Packet Repeat In TX mode, there is an option to send the FIFO contents repeatedly with a user-defined number of times to repeat. This is limited to the FIFO size, and the entire contents of the packet including preamble and sync word need to be loaded into the TX FIFO. This is selectable via the START_TX API, and packets will be sent without any gaps between them. 4.2.2.4. Direct Mode For legacy systems that perform packet handling within the host MCU or other baseband chip, it may not be desirable to use the FIFO. For this scenario, a Direct mode is provided, which bypasses the FIFOs entirely. In TX Direct mode, the TX modulation data is applied to an input pin of the chip and processed in "real time" (i.e., not stored in a register for transmission at a later time). Any of the GPIOs may be configured for use as the TX Data input function. Furthermore, an additional pin may be required for a TX Clock output function if GFSK modulation is desired (only the TX Data input pin is required for FSK or OOK). To achieve direct mode, the desired GPIO pin must be configured as a digital input by setting the GPIO_PIN_CFG API command = enumeration 0x04 in addition to setting the MODEM_MOD_TYPE API property to source the TXDATA stream from that same GPIO pin. For GFSK, "TX_DIRECT_MODE_TYPE" must be set to synchronous. For 2FSK or OOK, the type can be set to asynchronous or synchronous. The MOD_SOURCE[1:0] field within the MODEM_MOD_TYPE property should be set = 0x01h for all Direct mode configurations. In RX Direct mode, the RX Data and RX Clock can be programmed for direct (real-time) output to GPIO pins. The microcontroller may then process the RX data without using the FIFO or packet handler functions of the RFIC. Rev 1.0 25 Si4468/7 4.3. Preamble Length 4.3.1. Digital Signal Arrival Detector (DSA) Traditional preamble detection requires 20 preamble bits to detect a preamble. This device introduces a new approach to signal detection that can detect a preamble pattern in as little as one byte. If AFC is enabled, a preamble length of two bytes is sufficient to reliably detect signal arrival and settle a one-shot AFC. The impact of this is significant for low-power solutions as it reduces the amount of time the receiver has to stay active to detect the preamble. This feature is used with Preamble Sense Mode (see "8.6. Preamble Sense Mode" on page 42) and the latest WMBus N modes as well as with features, such as frequency hopping, which may use the DSA as a condition to hop. The traditional preamble detector is also available to maintain backward compatibility. Note that the DSA is using the RSSI jump detector. When used for collision detection, the RSSI jump detector may need to be reconfigured after preamble detection. Refer to the API documentation for details on how to configure the device to use the signal arrival detector. 4.3.2. Traditional Preamble Detection Optimal performance of the chip is obtained by qualifying reception of a valid Preamble pattern prior to continuing with reception of the remainder of the packet (e.g., Sync Word and Payload). Reception of the Preamble is considered valid when a minimum number of consecutive bits of 101010... pattern have been received; the required threshold for preamble detection is specified by the RX_THRESH[6:0] field in the PREAMBLE_CONFIG_STD_1 property. The appropriate value of the detection threshold depends upon the system application and typically trades off speed of acquisition against the probability of false detection. If the detection threshold is set too low, the chip may readily detect the short pattern within noise; the chip then proceeds to attempt to detect the remainder of the non-existent packet, with the result that the arrival of an actual valid packet may be missed. If the detection threshold is set too high, the required number of transmitted Preamble bits must be increased accordingly, leading to longer packet lengths and shorter battery life. A preamble detection threshold value of 20 bits is suitable for most applications. The total length of the transmitted Preamble field must be at least equal to the receive preamble detection threshold, plus an additional number of bits to allow for acquisition of bit timing and settling of the AFC algorithm. The recommended preamble detection thresholds and preamble lengths for a variety of operational modes are listed in Table 13. Configuration of the preamble detection threshold in the RX_THRESH[6:0] field is only required for reception of a standard Preamble pattern (i.e., 101010... pattern). Reception of a repetitive but non-standard Preamble pattern is also supported in the chip but is configured through the PREAMBLE_CONFIG_NSTD and PREAMBLE_PATTERN properties. 26 Rev 1.0 Si4468/7 Table 13. Recommended Preamble Length Mode AFC Antenna Diversity Preamble Type Recommended Preamble Length Recommended Preamble Detection Threshold (G)FSK Disabled Disabled Standard 4 Bytes 20 bits (G)FSK Enabled Disabled Standard 5 Bytes 20 bits (G)FSK Disabled Disabled Non-standard 2 Bytes 0 bits (G)FSK Enabled (G)FSK Disabled Enabled Standard 7 Bytes 24 bits (G)FSK Enabled Enabled Standard 8 Bytes 24 bits 4(G)FSK Disabled Disabled Standard 40 symbols 16 symbols 4(G)FSK Enabled Disabled Standard 48 symbols 16 symbols Non-standard 4(G)FSK Not Supported Non-standard Not Supported OOK Disabled Disabled Standard 4 Bytes 20 bits OOK Disabled Disabled Non-standard 2 Bytes 0 bits OOK Enabled Not Supported Notes: 1. The recommended preamble length and preamble detection thresholds listed above are to achieve 0% PER. They may be shortened when occasional packet errors are tolerable. 2. All recommended preamble lengths and detection thresholds include AGC and BCR settling times. 3. "Standard" preamble type should be set for an alternating data sequence at the max data rate (...10101010...) 4. "Non-standard" preamble type can be set for any preamble type including ...10101010... 5. When preamble detection threshold = 0, sync word needs to be 3 Bytes to avoid false syncs. When only a 2 Byte sync word is available the sync word detection can be extended by including the last preamble Byte into the RX sync word setting. Rev 1.0 27 Si4468/7 5. Internal Functional Blocks The following sections provide an overview to the key internal blocks and features. 5.1. RX Chain The internal low-noise amplifier (LNA) is designed to be a wide-band LNA that can be matched with three or four external discrete components to cover any common range of frequencies in the sub-GHz band. The LNA has extremely low noise to suppress the noise of the following stages and achieve optimal sensitivity; so, no external gain or front-end modules are necessary. The LNA has gain control, which is controlled by the internal automatic gain control (AGC) algorithm. The LNA is followed by an I-Q mixer, filter, programmable gain amplifier (PGA), and ADC. The I-Q mixers downconvert the signal to an intermediate frequency. The PGA then boosts the gain to be within dynamic range of the ADC. The ADC rejects out-of-band blockers and converts the signal to the digital domain where filtering, demodulation, and processing is performed. Peak detectors are integrated at the output of the LNA and PGA for use in the AGC algorithm. The RX and TX pins may be directly tied externally for output powers less than +17 dBm in the higher-frequency bands and can support +20 dBm in the lower bands, such as 169MHz. This reduces BOM cost by saving the expense of a switch for single antenna solutions. See the direct-tie reference designs on the Silicon Labs web site for more details. 5.1.1. RX Chain Architecture It is possible to operate the RX chain in different architecture configurations: fixed-IF, zero-IF, and scaled-IF. There are trade-offs between the architectures in terms of sensitivity, selectivity, and image rejection. Fixed-IF is the default configuration and is recommended for most applications. With 35 dB native image rejection and autonomous image calibration to achieve 55 dB, the fixed-IF solution gives the best performance for most applications. Fixed-IF obtains the best sensitivity, but it has the effect of degraded selectivity at the image frequency. An autonomous image rejection calibration is included in Si446x devices and described in more detail in "5.2.4. Image Rejection and Calibration" on page 30. For scaled-IF and zero-IF, the sensitivity is degraded for data rates less than 100 kbps or bandwidths less than 200 kHz. The reduction in sensitivity is caused by increased flicker noise as dc is approached. The benefit of zero-IF is that there is no image frequency; so, there is no degradation in the selectivity curve, but it has the worst sensitivity. Scaled-IF is a trade-off between fixed-IF and zero-IF. In the scaled-IF architecture, the image frequency is placed or hidden in the adjacent channel where it only slightly degrades the typical adjacent channel selectivity. The scaled-IF approach has better sensitivity than zero-IF but still some degradation in selectivity due to the image. In scaled-IF mode, the image frequency is directly proportional to the channel bandwidth selected. Figure 9 demonstrates the trade-off in sensitivity between the different architecture options. 1% PER sensitivity vs. data rate (h=1) -95 Sensitivity (dBm) -100 -105 Fixed IF Scaled IF -110 Zero IF -115 -120 1 10 100 Data rate (kbps) Figure 9. RX Architecture vs. Data Rate 28 Rev 1.0 Si4468/7 5.2. RX Modem Using high-performance ADCs allows channel filtering, image rejection, and demodulation to be performed in the digital domain, which allows for flexibility in optimizing the device for particular applications. The digital modem performs the following functions: Channel selection filter TX modulation RX demodulation Automatic Gain Control (AGC) Preamble detection Invalid preamble detection Radio signal strength indicator (RSSI) Automatic frequency compensation (AFC) Image Rejection Calibration Packet handling Cyclic redundancy check (CRC) Phase samples output The digital channel filter and demodulator are optimized for ultra-low-power consumption and are highly configurable. Supported modulation types are GFSK, FSK, 4GFSK, 4FSK, GMSK, and OOK. The channel filter can be configured to support bandwidths ranging from 850 kHz down to 200 Hz. A large variety of data rates are supported ranging from 100 bps up to 1 Mbps. The configurable preamble detector is used with the synchronous demodulator to improve the reliability of the sync-word detection. Preamble detection can be skipped using only sync detection, which is a valuable feature in some applications. The received signal strength indicator (RSSI) provides a measure of the signal strength received on the tuned channel. The resolution of the RSSI is 0.5 dB. This high-resolution RSSI enables accurate channel power measurements for clear channel assessment (CCA), carrier sense (CS), and listen before talk (LBT) functionality. A comprehensive programmable packet handler is integrated to create a variety of communication topologies ranging from peer-to-peer networks to mesh networks. The extensive programmability of the packet header allows for advanced packet filtering, which, in turn enables a mix of broadcast, group, and point-to-point communication. A wireless communication channel can be corrupted by noise and interference, so it is important to know if the received data is free of errors. A cyclic redundancy check (CRC) is used to detect the presence of erroneous bits in each packet. A CRC is computed and appended at the end of each transmitted packet and verified by the receiver to confirm that no errors have occurred. The packet handler and CRC can significantly reduce the load on the system microcontroller allowing for a simpler and cheaper microcontroller. The digital modem includes the TX modulator, which converts the TX data bits into the corresponding stream of digital modulation values to be summed with the fractional input to the sigma-delta modulator. This modulation approach results in highly accurate resolution of the frequency deviation. A Gaussian filter is implemented to support GFSK and 4GFSK, considerably reducing the energy in adjacent channels. The default bandwidth-time product (BT) is 0.5 for all programmed data rates, but it may be adjusted to other values. 5.2.1. Ultra Narrow Band (Long Range) Support The device is capable of supporting ultra-narrow bandwidths down to 200 Hz in all supported frequency bands. This is implemented by narrowing down the receive channel filter bandwidth in the device and can significantly improve link budget with a sensitivity of -133 dBm at 100 bps using 2GFSK modulation. These ultra-narrow bandwidths are useful for applications that need to transmit very small amounts of data, such as status information, over a very long range. Combined with standby current of 40 nA and transmit current of 18 mA at 10 dBm, a long-range, low-power solution can be achieved using the widely deployed and field-proven 2GFSK modulation. The range can be extended further by deploying the 20 dBm PA where the link budget would total 155 dB. A fast-scanning AFC is supported by using the frequency hop search feature, which alleviates the tolerance requirements of the crystal or TCXO. 5.2.2. Automatic Gain Control (AGC) The AGC algorithm is implemented digitally using an advanced control loop optimized for fast response time. The AGC occurs within a single bit or in less than 2 s. Peak detectors at the output of the LNA and PGA allow for optimal adjustment of the LNA gain and PGA gain to optimize IM3, selectivity, and sensitivity performance. Rev 1.0 29 Si4468/7 5.2.3. Auto Frequency Correction (AFC) Frequency mistuning caused by crystal inaccuracies can be compensated for by enabling the digital automatic frequency control (AFC) in receive mode. There are two types of integrated frequency compensation: modem frequency compensation and AFC by adjusting the PLL frequency. With AFC disabled, the modem compensation can correct for frequency offsets up to 0.25 times the IF bandwidth. When the AFC is enabled, the received signal is centered in the passband of the IF filter, providing optimal sensitivity and selectivity over a wider range of frequency offsets up to 0.35 times the IF bandwidth. When AFC is enabled, the preamble length needs to be long enough to settle the AFC. As shown in Table 13 on page 27, an additional byte of preamble is typically required to settle the AFC. 5.2.4. Image Rejection and Calibration Since the receiver utilizes a low-IF architecture, the selectivity will be affected by the image frequency. The IF frequency is 468.75 kHz (Fxtal/64), and the image frequency will be at 937.5 kHz (2 x Fxtal/64) below the RF frequency. The native image rejection of the Si446x family is 35 dB. Image rejection calibration is available in the Si446x to improve the image rejection to more than 55 dB. The calibration is initiated with the IRCAL API command. The calibration uses an internal signal source, so no external signal generator is required. The initial calibration takes 250 ms, and periodic re-calibration takes 100 ms. Recalibration should be initiated when the temperature has changed more than 30 C. 5.2.5. Received Signal Strength Indicator The received signal strength indicator (RSSI) is an estimate of the signal strength in the channel to which the receiver is tuned. The RSSI measurement is done after the channel filter, so it is only a measurement of the in-band signal power (desired or undesired). There are two methods for reading the RSSI value and several different options for configuring the returned RSSI value. The fastest method for reading the RSSI is to configure one of the four fast response registers (FRR) to return a latched RSSI value. The latched RSSI value is measured once per packet and is latched at a configurable amount of time after RX mode is entered. The fast response registers can be read in 16 SPI clock cycles with no requirement to wait for CTS. The RSSI value may also be read out of the GET_MODEM_STATUS command. In this command, both the current RSSI and the latched RSSI are available. The current RSSI value represents the signal strength at the instant in time the GET_MODEM_STATUS command is processed and may be read multiple times per packet. Reading the RSSI in the GET_MODEM_STATUS command takes longer than reading the RSSI out of the fast response register. After the initial command, it takes 33 s for CTS to be set and then the four or five bytes of SPI clock cycles to read out the respective current or latched RSSI values. The RSSI configuration options are set in the MODEM_RSSI_CONTROL API property. The latched RSSI value may be latched and stored based on the following events: preamble detection, sync detection, or a configurable number of bit times measured after the start of RX mode (minimum of 4 bit times). The requirement for a minimum of four bit times is determined by the processing delay and settling through the modem and digital channel filter. In MODEM_RSSI_CONTROL, the RSSI may be defined to update every bit period or to be averaged and updated every four bit periods. If RSSI averaging over four bits is enabled, the latched RSSI value will be delayed to a minimum of seven bits after the start of RX mode to allow for the averaging. The latched RSSI values are cleared when entering RX mode so they may be read after the packet is received or after dropping back to standby mode. If the RSSI value has been cleared by the start of RX but not yet latched, a value of 0 will be returned if it is attempted to be read. The RSSI value read by the API may be translated into dBm by the following linear equation: RF_Input_Level_dBm = (RSSI_value / 2) - MODEM_RSSI_COMP - 70 The MODEM_RSSI_COMP property provides for fine adjustment of the relationship between the actual RF input level (in dBm) and the returned RSSI value. That is, adjustment of this property allows the user to shift the RSSI vs RF Input Power curve up and down. This may be desirable to compensate for differences in front-end insertion loss between multiple designs (e.g., due to the presence of a SAW preselection filter, or an RF switch). A value of MODEM_RSSI_COMP = 0x40 = 64d is appropriate for most applications. Clear channel assessment (CCA) or RSSI threshold detection is also available. An RSSI threshold may be set in the MODEM_RSSI_THRESH API property. If the Current RSSI value is above this threshold, an interrupt or GPIO may notify the host. Both the latched version and asynchronous version of this threshold are available on any of the GPIOs. Automatic fast hopping based on RSSI is available. See "5.3.1.2. Automatic RX Hopping and Hop Table". 30 Rev 1.0 Si4468/7 5.2.6. RSSI Jump Indicator (Collision Detection) The chip is capable of detecting a jump in RSSI in either direction (i.e., either a signal increase or a signal decrease). Both polarities of jump detection may be enabled simultaneously, resulting in detection of a Jump-Up or Jump-Down event. This may be used to detect whether a secondary interfering signal (desired or undesired) has "collided" with reception of the current packet. An interrupt flag or GPIO pin may be configured to notify the host MCU of the Jump event. The change in RSSI level required to trigger the Jump event is programmable through the MODEM_RSSI_JUMP_THRESH API property. The chip may be configured to reset the RX state machine upon detection of an RSSI Jump, and thus to automatically begin reacquisition of the packet. The chip may also be configured to generate an interrupt. This functionality is intended to detect an abrupt change in RSSI level and to not respond to a slow, gradual change in RSSI level. This is accomplished by comparing the difference in RSSI level over a programmable time period. In this fashion, the chip effectively evaluates the slope of the change in RSSI level. The arrival of a desired packet (i.e., the transition from receiving noise to receiving a valid signal) will likely be detected as an RSSI Jump event. For this reason, it is recommended to enable this feature in mid-packet (i.e., after signal qualification, such as PREAMBLE_VALID.) Refer to the API documentation for configuration options. 5.2.7. Phase Samples Output To support proprietary demodulation schemes that require phase information, the device can provide phase samples in the form of a signed 8-bit value over the SPI interface. The radio generates a FIFO almost-full interrupt based on a user-defined FIFO threshold setting to indicate that phase samples are available. The effective data rate supported is limited by the SPI interface and the internal sample clock rate. The packet handler cannot be used simultaneously with this feature as the phase information is loaded into the RX FIFO. A majority of these applications are expected to use extremely low data rates. The host would need to further process the phase samples. 5.3. Synthesizer An integrated Sigma Delta () Fractional-N PLL synthesizer capable of operating over the bands from 142-175, 283-350, 350-525, and 850-1050 MHz. Using a synthesizer has many advantages; it provides flexibility in choosing data rate, deviation, channel frequency, and channel spacing. The transmit modulation is applied directly to the loop in the digital domain through the fractional divider, which results in very precise accuracy and control over the transmit deviation. The frequency resolution in the 850-1050 MHz band is 28.6 Hz with finer resolution in the other bands. The nominal reference frequency to the PLL is 30 MHz, but any XTAL frequency from 25 to 32 MHz may be used. The modem configuration calculator in WDS will automatically account for the XTAL frequency being used. The PLL utilizes a differential LC VCO with integrated on-chip inductors. The output of the VCO is followed by a configurable divider, which will divide the signal down to the desired output frequency band. 5.3.1. Synthesizer Frequency Control The frequency is set by changing the integer and fractional settings to the synthesizer. The WDS calculator will automatically provide these settings, but the synthesizer equation is shown below for convenience. The APIs for setting the frequency are FREQ_CONTROL_INTE, FREQ_CONTROL_FRAC2, FREQ_CONTROL_FRAC1, and FREQ_CONTROL_FRAC0. freq_xo fc_frac- 2 RF_channel = fc_inte + ---------------- ----------------------------- Hz 19 outdiv 2 Note: The fc_frac/219 value in the above formula has to be a number between 1 and 2. Rev 1.0 31 Si4468/7 Table 14. Output Divider (Outdiv) Values for the Si4468/7 Outdiv Lower (MHz) Upper (MHz) 24 142 175 12 284 350 10 350 420 8 420 525 4 850 1050 5.3.1.1. EZ Frequency Programming In applications that utilize multiple frequencies or channels, it may not be desirable to write four API registers each time a frequency change is required. EZ frequency programming is provided so that only a single register write (channel number) is required to change frequency. A base frequency is first set by first programming the integer and fractional components of the synthesizer. This base frequency will correspond to channel 0. Next, a channel step size is programmed into the FREQ_CONTROL_CHANNEL_STEP_SIZE_1 and FREQ_CONTROL_CHANNEL_STEP_SIZE_0 API registers. The resulting frequency will be: RF Frequency = Base Frequency + Channel Stepsi ze The second argument of the START_RX or START_TX is CHANNEL, which sets the channel number for EZ frequency programming. For example, if the channel step size is set to 1 MHz, the base frequency is set to 900 MHz with the FREQ_CONTROL_INTE and FREQ_CONTROL_FRAC API properties, and a CHANNEL number of 5 is programmed during the START_TX command, the resulting frequency will be 905 MHz. If no CHANNEL argument is written as part of the START_RX/TX command, it will default to the previously-programmed value. The initial value of CHANNEL is 0; so, if no CHANNEL value is written, it will result in the programmed base frequency. 5.3.1.2. Automatic RX Hopping and Hop Table The transceiver supports an automatic RX hopping feature that can be fully configured through the API. This functionality is useful in applications where it is desired to look for packets but to hop to the next channel if a packet is not found. The sequence of channel numbers that are visited are specified by entries in a hop table. If this feature is enabled, the device will automatically start hopping through the channels listed in the hop table as soon as the chip enters RX mode. The hop table can hold up to 64 entries and is maintained in firmware inside the RFIC. Each entry is a channel number, allowing construction of a frequency plan of up to 64 channels. The number of entries in the table is set by RX HOP TABLE_SIZE API. The specified channels correspond to the EZ frequency programming method for programming the frequency. The receiver starts at the base channel and hops in sequence from the top of the hop table to the bottom. The table will wrap around to the base channel once it reaches the end of the table. An entry of 0xFF in the table indicates that the entry should be skipped. The device will hop to the next entry in the table that contains a non-0xFF value. There are three conditions that can be used to determine whether to continue hopping or to stay on a particular channel. These conditions are as follows: RSSI threshold timeout (invalid preamble pattern) Sync word timeout (invalid or no sync word detected after preamble) These conditions can be used individually, or they can be enabled all together by configuring the RX_HOP_CONTROL API. However, the firmware will make a decision on whether or not to hop based on the first condition that is met. Preamble The RSSI that is monitored is the current RSSI value. This is compared to the threshold value set in the MODEM_RSSI_THRESH API property, and, if it is above the threshold value, it will stay on the channel. If the RSSI is below the threshold, it will continue hopping. There is no averaging of RSSI done during the automatic hopping from channel to channel. Since the preamble timeout and the sync word timeout are features that require 32 Rev 1.0 Si4468/7 packet handling, the RSSI threshold is the only condition that can be used if the user is in "direct" or "RAW" mode where packet handling features are not used. The RSSI threshold value may be converted to an approximate equivalent RF input power level through the equation shown in "5.2.5. Received Signal Strength Indicator" on page 30. However, performance should be verified on the bench to optimize the threshold setting for a given application. The time spent in receive mode will be determined by the configuration of the hop conditions. Manual RX hopping will have the fastest turn-around time but will require more overhead and management by the host MCU. The following are example steps for using Auto Hop: 1. Set the base frequency (inte + frac) and channel step size. 2. Define the number of entries in the hop table (RX_HOP_TABLE_SIZE). 3. Write the channels to the hop table (RX_HOP_TABLE_ENTRY_n) 4. Configure the hop condition and enable auto hopping- RSSI, preamble, or sync (RX_HOP_CONTROL). 5. Set preamble and sync parameters if enabled. 6. Program the RSSI threshold property in the modem using "MODEM_RSSI_THRESH". 7. Set the preamble threshold using "PREAMBLE_CONFIG_STD_1". 8. Program the preamble timeout property using "PREAMBLE_CONFIG_STD_2". 9. Set the sync detection parameters if enabled. 10. If needed, use "GPIO_PIN_CFG" to configure a GPIO to toggle on hop and hop table wrap. 11. Use the "START_RX" API with channel number set to the first valid entry in the hop table (i.e., the first non 0xFF entry). 12. Device should now be in auto hop mode. 5.3.1.3. Manual RX Hopping The RX_HOP command provides the fastest method for hopping from RX to RX but it requires more overhead and management by the host MCU. The timing is faster with this method than Start_RX or RX hopping because one of the calculations required for the synthesizer calibrations is offloaded to the host and must be calculated/stored by the host, VCO_CNT0. For VCO_CNT values, download the Si446x RX_HOP PLL calculator spreadsheet from the Si446x product website. 5.4. Transmitter (TX) The Si4468 contains an integrated +20 dBm transmitter or power amplifier that is capable of transmitting from -20 to +20 dBm. The resolution of the programmable steps in output power is less than 0.25 dB when operated within 6 dB of the maximum power setting; the resolution of the steps in output power becomes coarser and more non-linear as the output power is reduced towards the minimum end of its control range. The Si4468 PA is designed to provide the highest efficiency and lowest current consumption possible. The Si4467 is designed to supply +10 dBm output power for less than 20 mA for applications that require operation from a single coin cell battery. The Si4467 can operate with Class-E matching and output up to +13 dBm Tx power at a supply voltage of VDD = 3.3 V. All PA options are single-ended to allow for easy antenna matching and low BOM cost. Automatic ramp-up and ramp-down is automatically performed to reduce unwanted spectral spreading. Refer to "AN627: Si4460/61 Low-Power PA Matching" and "AN648: PA Matching" for details on TX matching options. The chip's TXRAMP pin is disabled by default to save current in cases where the on-chip PA provides sufficient output power to drive the antenna. In cases where on-chip PA will drive the external PA, and the external PA needs a ramping signal, TXRAMP is the signal to use. To enable TXRAMP, set the API Property PA_MODE[7] = 1. TXRAMP will start to ramp up, and ramp down at the SAME time as the internal on-chip PA ramps up/down. However, the time constant of the TXRAMP signal for the external PA is programmed independently of the ramp time constant for the on-chip PA. The ramp time constant for TXRAMP is programmed by the TC[3:0] field in the PA_RAMP_EX API property and provides the following approximate ramp times as a function of TC[3:0] value. Rev 1.0 33 Si4468/7 Table 15. Ramp Times as a Function of TC[3:0] Value TC Ramp Time (s) 0 1.25 1 1.33 2 1.43 3 1.54 4 1.67 5 1.82 6 2.00 7 2.22 8 2.50 9 2.86 10 3.33 11 4.00 12 5.00 13 6.67 14 10.00 15 20.00 The ramping profile is close to a linear ramping profile with smoothed out corner when approaching Vhi and Vlo. The TXRAMP pin can source up to 1 mA without voltage drooping. The TXRAMP pin's sinking capability is equivalent to a 10 k pull-down resistor. Vhi = 3 V when Vdd > 3.3 V. When Vdd < 3.3 V, the Vhi will be closely following the Vdd, and ramping time will be smaller also. Vlo = 0 V when NO current needed to be sunk into TXRAMP pin. If 10uA need to be sunk into the chip, Vlo will be 10 A x 10k = 100 mV. 34 Number Command Summary 0x2200 PA_MODE 0x2201 PA_PWR_LVL 0x2202 PA_BIAS_CLKDUTY Adjust TX power in coarse steps and optimizes for different match configurations. 0x2203 PA_TC Changes the ramp up/down time of the PA. Sets PA type. Adjust TX power in fine steps. Rev 1.0 Si4468/7 5.4.1. Si4468: +20 dBm PA The +20 dBm configuration utilizes a class-E matching configuration for all frequency bands except 169 MHz where it uses a Square Wave match..Typical performance for the 915 MHz band for output power steps, voltage, and temperature are shown in Figures 10-12. The output power is changed in 128 steps through PA_PWR_LVL API. For detailed matching values, BOM, and performance at other frequencies, refer to "AN648: PA Matching". TXPowervs.PA_PWR_LVL 25 20 15 10 5 5 10 15 20 25 30 35 40 0 20 40 60 80 100 120 PA_PWR_LVL Figure 10. +20 dBm TX Power vs. PA_PWR_LVL TX Power vs. VDD 22 TX Power (dBm) TXPower(dBm) 0 20 18 16 14 12 10 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 Supply Voltage (VDD) Figure 11. +20 dBm TX Power vs. VDD Rev 1.0 35 Si4468/7 TX Power vs Temp TX Power (dBm) 20.5 20 19.5 19 18.5 18 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 Temperature (C) Figure 12. +20 dBm TX Power vs. Temp 5.5. Crystal Oscillator The Si446x includes an integrated crystal oscillator with a fast start-up time of less than 250 s. The design is differential with the required crystal load capacitance integrated on-chip to minimize the number of external components. By default, all that is required off-chip is the crystal. The default crystal is 30 MHz, but the circuit is designed to handle any XTAL from 25 to 32 MHz. If a crystal different than 30 MHz is used, the POWER_UP API boot command must be modified. The WDS calculator crystal frequency field must also be changed to reflect the frequency being used. The crystal load capacitance can be digitally programmed to accommodate crystals with various load capacitance requirements and to adjust the frequency of the crystal oscillator. The tuning of the crystal load capacitance is programmed through the GLOBAL_XO_TUNE API property. The total internal capacitance is 11 pF and is adjustable in 127 steps (70 fF/step). The crystal frequency adjustment can be used to compensate for crystal production tolerances. The frequency offset characteristics of the capacitor bank are demonstrated in Figure 13. Figure 13. Capacitor Bank Frequency Offset Characteristics 36 Rev 1.0 Si4468/7 Utilizing the on-chip temperature sensor and suitable control software, the temperature dependency of the crystal can be canceled. A TCXO or external signal source can easily be used in place of a conventional XTAL and should be connected to the XIN pin. The incoming clock signal is recommended to have a peak-to-peak swing in the range of 600 mV to 1.4 V and ac-coupled to the XIN pin. If the peak-to-peak swing of the TCXO exceeds 1.4 V peak-to-peak, then dc coupling to the XIN pin should be used. The maximum allowed swing on XIN is 1.8 V peak-to-peak. The XO capacitor bank should be set to 0 whenever an external drive is used on the XIN pin. In addition, the POWER_UP command should be invoked with the TCXO option whenever external drive is used. Rev 1.0 37 Si4468/7 6. Data Handling and Packet Handler 6.1. RX and TX FIFOs Two 64-byte FIFOs are integrated into the chip, one for RX and one for TX, as shown in Figure 14. For dedicated TX or RX, the FIFO size is up to 129 bytes. Writing to command Register 66h loads data into the TX FIFO, and reading from command Register 77h reads data from the RX FIFO. The TX FIFO has a threshold for when the FIFO is almost empty, which is set by the "TX_FIFO_EMPTY" property. An interrupt event occurs when the data in the TX FIFO reaches the almost empty threshold. If more data is not loaded into the FIFO, the chip automatically exits the TX state after the PACKET_SENT interrupt occurs. The RX FIFO has one programmable threshold, which is programmed by setting the "RX_FIFO_FULL" property. When the incoming RX data crosses the Almost Full Threshold, an interrupt will be generated to the microcontroller via the nIRQ pin. The microcontroller will then need to read the data from the RX FIFO. The RX Almost Full Threshold indication implies that the host can read at least the threshold number of bytes from the RX FIFO at that time. Both the TX and RX FIFOs may be cleared or reset with the "FIFO_RESET" command. RX FIFO TX FIFO RX FIFO Almost Full Threshold TX FIFO Almost Empty Threshold Figure 14. TX and RX FIFOs 6.2. Packet Handler Config 0, 2, o r 4 Bytes Con fig 0, 2, o r 4 Bytes Rev 1.0 0, 2, o r 4 B ytes C RC Field 5 (op t) Field 5 (opt) Data C RC Field 4 (op t) Con fig Figure 15. Packet Handler Structure 38 Field 4 (opt) Data C RC Field 3 (op t) Field 3 (opt) Data Con fig C RC Field 2 (op t) 1-4 Bytes F ield 2 (o pt) Pkt Len gth or Data Field 1 Header or Data 1-255 Bytes C RC Field 1 (op t) Preamble Sync Word When using the FIFOs, automatic packet handling may be enabled for TX mode, RX mode, or both. The usual fields for network communication, such as preamble, synchronization word, headers, packet length, and CRC, can be configured to be automatically added to the data payload. The fields needed for packet generation normally change infrequently and can therefore be stored in registers. Automatically adding these fields to the data payload in TX mode and automatically checking them in RX mode greatly reduces the amount of communication between the microcontroller and Si446x. It also greatly reduces the required computational power of the microcontroller. The general packet structure is shown in Figure 15. Any or all of the fields can be enabled and checked by the internal packet handler. Con fig 0, 2, or 4 Bytes 0, 2, or 4 Bytes Si4468/7 The fields are highly programmable and can be used to check any kind of pattern in a packet structure. The general functions of the packet handler include the following: Detection/validation of Preamble quality in RX mode (PREAMBLE_VALID signal) of Sync word in RX mode (SYNC_OK signal) Detection of valid packets in RX mode (PKT_VALID signal) Detection of CRC errors in RX mode (CRC_ERR signal) Data de-whitening and/or Manchester decoding (if enabled) in RX mode Match/Header checking in RX mode Storage of Data Field bytes into FIFO memory in RX mode Construction of Preamble field in TX mode Construction of Sync field in TX mode Construction of Data Field from FIFO memory in TX mode Construction of CRC field (if enabled) in TX mode Data whitening and/or Manchester encoding (if enabled) in TX mode For details on how to configure the packet handler, see "AN626: Packet Handler Operation for Si446x RFICs". Detection Rev 1.0 39 Si4468/7 7. RX Modem Configuration The Si446x can easily be configured for different data rate, deviation, frequency, etc. by using the Radio Configuration Application (RCA) GUI which is part of the Wireless Development Suite (WDS) program. 8. Auxiliary Blocks 8.1. Wake-up Timer and 32 kHz Clock Source The chip contains an integrated wake-up timer that can be used to periodically wake the chip from sleep mode. The wake-up timer runs from either the internal 32 kHz RC Oscillator, or from an external 32 kHz XTAL. The wake-up timer can be configured to run when in sleep mode. If WUT_EN = 1 in the GLOBAL_WUT_CONFIG property, prior to entering sleep mode, the wake-up timer will count for a time specified defined by the GLOBAL_WUT_R and GLOBAL_WUT_M properties. At the expiration of this period, an interrupt will be generated on the nIRQ pin if this interrupt is enabled in the INT_CTL_CHIP_ENABLE property. The microcontroller will then need to verify the interrupt by reading the chip interrupt status either via GET_INT_STATUS or a fast response register. The formula for calculating the Wake-Up Period is as follows: WUT_R 42 WUT = WUT_M ----------------------------- ms 32.768 The RC oscillator frequency will change with temperature; so, a periodic recalibration is required. The RC oscillator is automatically calibrated during the POWER_UP command and exits from the Shutdown state. To enable the recalibration feature, CAL_EN must be set in the GLOBAL_WUT_CONFIG property, and the desired calibration period should be selected via WUT_CAL_PERIOD[2:0] in the same API property. During the calibration, the 32 kHz RC oscillator frequency is compared to the 30 MHz XTAL and then adjusted accordingly. The calibration needs to start the 30 MHz XTAL, which increases the average current consumption; so, a longer CAL_PERIOD results in a lower average current consumption. The 32 kHz XTAL accuracy is comprised of both the XTAL parameters and the internal circuit. The XTAL accuracy can be defined as the XTAL initial error + XTAL aging + XTAL temperature drift + detuning from the internal oscillator circuit. The error caused by the internal circuit is typically less than 10 ppm. Refer to API documentation for details on WUT related commands and properties. 8.2. Low Duty Cycle Mode (Auto RX Wake-Up) The low duty cycle (LDC) mode is implemented to automatically wake-up the receiver to check if a valid signal is available or to enable the transmitter to send a packet. It allows low average current polling operation by the Si446x for which the wake-up timer (WUT) is used. RX and TX LDC operation must be set via the GLOBAL_WUT_CONFIG property when setting up the WUT. The LDC wake-up period is determined by the following formula: WUT_R 42 LDC = WUT_LDC ----------------------------- ms 32.768 where the WUT_LDC parameter can be set by the GLOBAL_WUT_LDC property. The WUT period must be set in conjunction with the LDC mode duration; for the relevant API properties, see the wake-up timer (WUT) section. 40 Rev 1.0 Si4468/7 Figure 16. RX and TX LDC Sequences The basic operation of RX LDC mode is shown in Figure 17. The receiver periodically wakes itself up to work on RX_STATE during LDC mode duration. If a valid preamble is not detected, a receive error is detected, or an entire packet is not received, the receiver returns to the WUT state (i.e., ready or sleep) at the end of LDC mode duration and remains in that mode until the beginning of the next wake-up period. If a valid preamble or sync word is detected, the receiver delays the LDC mode duration to receive the entire packet. If a packet is not received during two LDC mode durations, the receiver returns to the WUT state at the last LDC mode duration until the beginning of the next wake-up period. Figure 17. Low Duty Cycle Mode for RX In TX LDC mode, the transmitter periodically wakes itself up to transmit a packet that is in the data buffer. If a packet has been transmitted, nIRQ goes low if the option is set in the INT_CTL_ENABLE property. After transmitting, the transmitter immediately returns to the WUT state and stays there until the next wake-up time expires. Rev 1.0 41 Si4468/7 8.3. Temperature, Battery Voltage, and Auxiliary ADC The Si446x family contains an integrated auxiliary ADC for measuring internal battery voltage, an internal temperature sensor, or an external component over a GPIO. The ADC utilizes a SAR architecture and achieves 11-bit resolution. The Effective Number of Bits (ENOB) is 9 bits. When measuring external components, the input voltage range is 1 V, and the conversion rate is between 300 Hz to 2.44 kHz. The ADC value is read by first sending the GET_ADC_READING command and enabling the inputs that are desired to be read: GPIO, battery, or temp. The temperature sensor accuracy at 25 C is typically 2 C. Refer to API documentation for details on the command and reply stream. 8.4. Low Battery Detector The low battery detector (LBD) is enabled and utilized as part of the wake-up-timer (WUT). The LBD function is not available unless the WUT is enabled, but the host MCU can manually check the battery voltage anytime with the auxiliary ADC. The LBD function is enabled in the GLOBAL_WUT_CONFIG API property. The battery voltage will be compared against the threshold each time the WUT expires. The threshold for the LBD function is set in GLOBAL_LOW_BATT_THRESH. The threshold steps are in increments of 50 mV, ranging from a minimum of 1.5 V up to 3.05 V. The accuracy of the LBD is 3%. The LBD notification can be configured as an interrupt on the nIRQ pin or enabled as a direct function on one of the GPIOs. 8.5. Antenna Diversity To mitigate the problem of frequency-selective fading due to multipath propagation, some transceiver systems use a scheme known as antenna diversity. In this scheme, two antennas are used. Each time the transceiver enters RX mode the receive signal strength from each antenna is evaluated. This evaluation process takes place during the preamble portion of the packet. The antenna with the strongest received signal is then used for the remainder of that RX packet. The same antenna will also be used for the next corresponding TX packet. This chip fully supports antenna diversity with an integrated antenna diversity control algorithm. The required signals needed to control an external SPDT RF switch (such as a PIN diode or GaAs switch) are available on the GPIOx pins. The operation of these GPIO signals is programmable to allow for different antenna diversity architectures and configurations. The antdiv[2:0] bits are found in the MODEM_ANT_DIV_CONTROL API property descriptions and enable the antenna diversity mode. The GPIO pins are capable of sourcing up to 5 mA of current; so, it may be used directly to forward-bias a PIN diode if desired. The antenna diversity algorithm will automatically toggle back and forth between the antennas until the packet starts to arrive. The recommended preamble length for optimal antenna selection is 8 bytes. 8.6. Preamble Sense Mode This mode of operation is suitable for extremely low power applications where power consumption is important. The preamble sense mode (PSM) takes advantage of the Digital Signal Arrival detector (DSA), which can detect a preamble within eight bit times with no sensitivity degradation. This fast detection of an incoming signal can be combined with duty cycling of the receiver during the time the device is searching or sniffing for packets over the air. The average receive current is lowered significantly when using this mode. In applications where the timing of the incoming signal is unknown, the amount of power savings is primarily dependent on the data rate and preamble length as the RX inactive time is determined by these factors. In applications where the sleep time is fixed and the timing of the incoming signal is known, the average current also depends on the sleep time. The PSM mode is similar to the low duty cycle mode but has the benefit of faster signal detection and autonomous duty cycling of the receiver to achieve even lower average receive currents. This mode can be used with the low power mode (LP) which has an active RX current of 10 mA or with the high-performance (HP) mode which has an active RX current of 13 mA. 42 Rev 1.0 Si4468/7 Figure 18. Preamble Sense Mode Table 16. Data Rates Data Rate 1.2 kbps 9.6 kbps 50 kbps 100 kbps PM length = 4 bytes 6.48 6.84 8.44 10.43 mA PM length = 8 bytes 3.83 3.96 4.57 5.33 mA Note: Typical values. Active RX current is 13 mA. Rev 1.0 43 Si4468/7 9. Standards Support 9.1. Wireless MBus Support Wireless MBus is a widely accepted standard for smart meter communication in Europe. The radio supports all WMBus modes per the latest draft specification of the EN13757-4 standard. This includes a much wider deviation error tolerance of 30% and frequency error tolerance of 4 kHz, short preamble support (16-bit preamble for 2 and 4 level FSK modes), 3-of-6 encoding and decoding and 169 MHz N modes including N2g. In addition, Silicon Labs has a production-ready wireless MBus stack available at no additional cost that supports S, T, C, and N modes and runs on the EFM32 (32-bit ARM) family of energy friendly microcontrollers. This stack and complete documentation including PHY configuration and test results are available for download from the EZRadioPRO page at www.silabs.com. 9.2. ETSI EN300 220 Category 1 The radio is capable of supporting ETSI Category 1 applications (social alarms, healthcare applications, etc.) in the 169 MHz and 868 MHz bands under certain modem conditions. Blocking performance is improved at the 2 MHz and 10 MHz offsets allowing for additional margin from the regulatory limits. The radio complies with ACS limits at the 25 kHz offset in both, 169 MHz and 868 MHz bands. In the 169 MHz band, there is no need for an external SAW filter for 2 MHz and 10 MHz blocking resulting in a lower system cost. In the 868 MHz band, an external SAW filter is still required to meet the Cat 1 blocking limits. An RF Pico board is available for evaluation specifically for ETSI Cat 1 applications. Test conditions for ETSI Cat 1 specifications are different from the typical conditions and are stated below. Data Rate: 3 kbps Deviation: 2 kHz Modulation: 2 GFSK IF mode: Fixed and/or Scaled IF RX bandwidth: 13 kHz BER target: 0.1% Blocker signal: CW ETSI Cat 1 limits 169 MHz band (no SAW) 868 MHz band (no SAW) 25 kHz ACS 54 dB 62 dB 58 dB 2 MHz blocking 84 dB 88 dB 76 dB 10 MHz blocking 84 dB 90 dB 82 dB RX sensitivity -107 dBm -108 dBm -108 dBm Spurious response 35 dB 40 dB 40 dB For further details on configuring the radio for ETSI Cat 1 applications, refer to the application notes available on the Silicon Labs website. 44 Rev 1.0 Si4468/7 9.3. IEEE 802.15.4 Support Si4468/7 supports the mandatory features of MR-FSK PHY specified in IEEE 802.15.4g as well as some key features from IEEE 802.15.4. The high level of integration makes it easy to use and offloads the host microcontroller from these tasks. To support the 802.15.4 MAC, the device has a specific 802.15.4 boot mode. In this mode, the device only processes 802.15.4 / 4g packets and no customization is possible at the packet level. This mode is supported by an 802.15.4 stack running on a Silicon Labs MCU or SoC. In this mode, the device only supports the packet format defined in the 802.15.4 standard. There is no flexibility to support non-802.15.4 packet formats in this boot mode. Custom packets, including those based on the 802.15.4g PHY standard, are fully supported in the EZRadioPRO boot mode. 802.15.4g PHY modes including CRC handling and dual sync word are supported in the PRO boot mode as well. The key features are described below. 9.3.1. CCA Functionality Basic clear channel assessment (CCA) functionality is supported in any boot mode and relies on RSSI being above or below a user defined threshold. In addition, the chip supports CSMA / CA and Energy Detection (ED) as defined in IEEE 802.15.4. 9.3.2. CSMA/CA The carrier sense feature is fully supported in the 802.15.4 boot mode of the device and is specific to the 802.15.4 packet format. Support for CSMA/CA in the EZRadioPRO boot mode requires host microcontroller support to implement the back-off timer. The device can send an IEEE 802.15.4 packet with a CSMA/CA algorithm before the packet and reception of an ACK packet afterwards without host interaction. The host loads the IEEE 802.15.4 packet into the TX FIFO via the WRITE_TX_FIFO command. The CSMA/CA algorithm must pass before sending the packet configured, the transceiver will listen for an ACK after successful transmission of the packet The CSMA/CA algorithm listens on the transmit channel to see if the channel is clear before transmitting the packet. The period in which the transceiver listens is defined in units of symbols. If the RSSI measured is greater than a user-defined threshold, the transceiver deems that the channel is busy and does a backoff for a random amount of time up to five backoff periods. The units of the backoff are defined in symbol times. If the channel is clear during the listening period, then the transceiver will proceed to transmit the IEEE 802.15.4 packet. If the transceiver exhausts all of the backoff periods, the transceiver will post a TX_ERROR interrupt with a TX_ERROR_STATUS of CCA_FAIL. If Below is an example of a transmit operation where the first CSMA check fails and the second one passes. Rev 1.0 45 Si4468/7 Figure 19. Transmit Operation where first CSMA Check Fails and Second Passes The device also supports Listen Before Talk (LBT) as defined by the ETSI EN 300 220-1 specification, which adds a minimum (fixed) 5 ms delay in addition to a random backoff before transmission. 9.3.3. Auto-ACK After the packet is transmitted, the transceiver has the ability to automatically receive an ACK if configured to do so. The transceiver will listen for a properly formatted acknowledgement frame with a set timeout period. If the ACK is received in time, the transceiver will post an interrupt depending on if the frame pending bit is set in the ACK. If the ACK is not received in the timeout window, the transceiver will post a TX_ERROR interrupt. 9.3.4. 802.15.4 Packet Format The device supports the frame format defined in IEEE 802.15.4 and is able to parse the field information autonomously without host interaction. All the host needs to do is boot up in the 802.15.4 boot mode and load the packet into the TX FIFO for transmission. For details on the 802.15.4 packet formats, please refer to the standard's documentation. 9.3.5. 802.15.4g CRC The device natively supports both 2 byte and 4 byte FCS as defined in IEEE 802.15.4g in both boot modes. 9.3.6. Simultaneous Dual Sync Word The device is capable of simultaneously searching for two sync words with each sync word being user defined and up to 4 bytes each. One application of this is to detect packets that use forward error correction (FEC) as defined in IEEE 802.15.4g. FEC is an optional feature in the standard is indicated in the sync word. The transceiver does not natively support FEC. It can pass on the information on whether FEC is used or not to the host microcontroller for further processing. 9.3.7. Address Filtering The device supports 8 byte (EUI-64) address filtering per IEEE 802.15.4. This is a unique identifier that is used for each node in a network. The device also supports the short address filtering defined in the 802.15.4 standard. 46 Rev 1.0 Si4468/7 10. Packet Trace Port The device integrates a true PHY-level Packet Trace Interface (PTI) for effective network-level debugging. PTI monitors all the PHY Tx and Rx packets without affecting their normal operation. This asynchronous interface provides a trace of all over-the-air packet data as well as packet status via a single user-selectable GPIO. PTI can be disabled in software and cannot be used to inject packets into the modem interface. The default baud rate of the PTI interface is 500 kbaud, which is optimal to support a 250 kbps data rate. PTI is supported on Si4468/7 in the 15.4 boot mode only and is supported by Silicon Labs Development tools. Rev 1.0 47 Si4468/7 GND XIN XOUT 1 GPIO2 SDN GPIO3 11. Pin Descriptions: Si4468/7 20 19 18 17 16 RXp 2 15 nSEL RXn 3 14 SDI GND PAD TX 4 13 SDO Pin Pin Name 6 7 8 9 10 TXRamp VDD GPIO0 GPIO1 12 SCLK VDD NC 5 11 nIRQ I/0 Description 1 SDN I Shutdown Input Pin. 0-VDD V digital input. SDN should be = 0 in all modes except Shutdown mode. When SDN = 1, the chip will be completely shut down, and the contents of the registers will be lost. 2 RXp I Differential RF Input Pins of the LNA. 3 RXn I See application schematic for example matching network. 4 TX O 5 NC 6 VDD VDD 7 TXRAMP O 8 VDD VDD 9 GPIO0 I/O General Purpose Digital I/O. I/O May be configured through the registers to perform various functions including: Microcontroller Clock Output, FIFO status, POR, Wake-Up timer, Low Battery Detect, TRSW, AntDiversity control, etc. Transmit Output Pin. 10 GPIO1 The PA output is an open-drain connection, so the L-C match must supply VDD (+3.3 VDC nominal) to this pin. It is recommended to connect to GND per the reference design schematic. Not connected internally to any circuitry. +1.8 to +3.8 V Supply Voltage Input to Internal Regulators. The recommended VDD supply voltage is +3.3 V. Programmable Bias Output with Ramp Capability for External FET PA. See "5.4. Transmitter (TX)" on page 33. +1.8 to +3.8 V Supply Voltage Input to Internal Regulators. The recommended VDD supply voltage is +3.3 V. General Microcontroller Interrupt Status Output. 11 48 nIRQ O When the Si446X exhibits any one of the interrupt events, the nIRQ pin will be set low = 0. The Microcontroller can then determine the state of the interrupt by reading the interrupt status. No external resistor pull-up is required, but it may be desirable if multiple interrupt lines are connected. Rev 1.0 Si4468/7 Pin Pin Name I/0 Description Serial Clock Input. 12 SCLK I 13 SDO O 0-VDD V digital input. This pin provides the serial data clock function for the 4-line serial data bus. Data is clocked into the Si446x on positive edge transitions. 0-VDD V Digital Output. Provides a serial readback function of the internal control registers. Serial Data Input. 14 SDI I 0-VDD V digital input. This pin provides the serial data stream for the 4-line serial data bus. Serial Interface Select Input. 15 nSEL I 0-VDD V digital input. This pin provides the Select/Enable function for the 4-line serial data bus. Crystal Oscillator Output. 16 XOUT O 17 XIN I Connect to an external 25 to 32 MHz crystal, or leave floating when driving with an external source on XIN. Crystal Oscillator Input. Connect to an external 25 to 32 MHz crystal, or connect to an external source. When using an XTAL, leave floating per the reference design schematic. When using a TCXO, connect to TCXO GND, which should be separate from the board's reference ground plane. 18 GND GND 19 GPIO2 I/O General Purpose Digital I/O. 20 GPIO3 I/O May be configured through the registers to perform various functions, including Microcontroller Clock Output, FIFO status, POR, Wake-Up timer, Low Battery Detect, TRSW, AntDiversity control, etc. GND The exposed metal paddle on the bottom of the Si446x supplies the RF and circuit ground(s) for the entire chip. It is very important that a good solder connection is made between this exposed metal paddle and the ground plane of the PCB underlying the Si446x. PKG PADDLE_GND Rev 1.0 49 Si4468/7 12. Ordering Information Part Number Description Package Type Operating Temperature Si4468-A2A-IM ISM EZRadioPRO Transceiver QFNPb-free -40 to 125 C Si4467-A2A-IM ISM EZRadioPRO Transceiver QFNPb-free -40 to 125 C Note: Add an "(R)" at the end of the device part number to denote tape and reel option. 50 Rev 1.0 Si4468/7 13. Package Outline: Si4468/7 Figure 20 illustrates the package details for the Si446x. Table 17 lists the values for the dimensions shown in the illustration. 2X bbb C B A D D2 Pin 1 (Laser) e 20 20x L 1 E E2 2X aaa C A1 20x b ccc C ddd C A B eee C A SEATING PLANE A3 C Figure 20. 20-Pin Quad Flat No-Lead (QFN) Rev 1.0 51 Si4468/7 Table 17. Package Dimensions Dimension Min Nom Max A 0.80 0.85 0.90 A1 0.00 0.02 0.05 A3 b 0.20 REF 0.18 0.25 D D2 0.30 4.00 BSC 2.45 2.60 e 0.50 BSC E 4.00 BSC 2.75 E2 2.45 2.60 2.75 L 0.30 0.40 0.50 aaa 0.15 bbb 0.15 ccc 0.10 ddd 0.10 eee 0.08 Notes: 1. All dimensions are shown in millimeters (mm) unless otherwise noted. 2. Dimensioning and tolerancing per ANSI Y14.5M-1994. 3. This drawing conforms to the JEDEC Solid State Outline MO-220, Variation VGGD-8. 4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. 52 Rev 1.0 Si4468/7 14. PCB Land Pattern: Si4468/7 Figure 21 illustrates the PCB land pattern details for the Si446x. Table 18 lists the values for the dimensions shown in the illustration. Figure 21. PCB Land Pattern Rev 1.0 53 Si4468/7 Table 18. PCB Land Pattern Dimensions Symbol Millimeters Min Max C1 3.90 4.00 C2 3.90 4.00 E 0.50 REF X1 0.20 0.30 X2 2.55 2.65 Y1 0.65 0.75 Y2 2.55 2.65 Notes: General 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. This land pattern design is based on IPC-7351 guidelines. Solder Mask Design 3. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60 m minimum, all the way around the pad. Stencil Design 4. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 5. The stencil thickness should be 0.125 mm (5 mils). 6. The ratio of stencil aperture to land pad size should be 1:1 for the perimeter pads. 7. A 2x2 array of 1.10 x 1.10 mm openings on 1.30 mm pitch should be used for the center ground pad. Card Assembly 8. A No-Clean, Type-3 solder paste is recommended. 9. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for small body components. 54 Rev 1.0 Si4468/7 15. Top Marking 15.1. Si4468/7 Top Marking 15.2. Top Marking Explanation Mark Method YAG Laser Line 1 Marking Part Number 44682A = Si4468 Rev A21 44672A = Si4467 Rev A21 Line 2 Marking TTTTTT = Internal Code Internal tracking code.2 Line 3 Marking YY = Year WW = Workweek Assigned by the Assembly House. Corresponds to the last significant digit of the year and workweek of the mold date. Notes: 1. The first letter after the part number is part of the ROM revision. The last letter indicates the firmware revision. 2. The first letter of this line is part of the ROM revision. Rev 1.0 55 Si4468/7 DOCUMENT CHANGE LIST Revision 0.1 to Revision 1.0 Updated parameters and notes in "1. Electrical Specifications". Updated Table 15. Updated "11. Pin Descriptions: Si4468/7". Minor updates to text descriptions. 56 Rev 1.0 Simplicity Studio One-click access to MCU tools, documentation, software, source code libraries & more. Available for Windows, Mac and Linux! www.silabs.com/simplicity MCU Portfolio www.silabs.com/mcu SW/HW www.silabs.com/simplicity Quality www.silabs.com/quality Support and Community community.silabs.com Disclaimer Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific written consent of Silicon Laboratories. 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