ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 Two 1-Bit, 10MHz, 2nd-Order Delta-Sigma Modulators Check for Samples: ADS1209 FEATURES DESCRIPTION * * * * * * * * * * The ADS1209 is a two-channel, high-performance, delta-sigma () modulator with an 86dB dynamic range, operating from a single +5V supply. The differential inputs are ideal for direct connection to signal sources in an industrial environment. With the appropriate digital filter and modulator rate, the device can be used to achieve 16-bit analog-to-digital (A/D) conversion with no missing codes. Effective accuracy of 14 bits can be obtained with a digital filter bandwidth of 20kHz at a modulator rate of 10MHz. The ADS1209 is designed for use in high-resolution measurement applications including current measurements, industrial process control, and resolvers. It is available in a TSSOP-24 package and is specified for operation over the ambient temperature range of -40C to +105C. 1 2 * 16-Bit Resolution 13-Bit Linearity 2.3V Specified Input Voltage Range Internal Reference Voltage: 2% Gain Error: 0.5% Two Independent Delta-Sigma Modulators Two Input Reference Buffers On-Chip Oscillator Selectable Internal or External Clock Specified Temperature Range: -40C to +105C TSSOP-24 Package APPLICATIONS * * * * * Motor Control Current Measurement Resolver Industrial Process Control Instrumentation AVDD CHA+ CHA- 2nd-Order DS Modulator BVDD OUTA Output Interface Circuit CLKOUT REFINA CHB+ CHB- OUTB 2nd-Order DS Modulator Divider REFINB Clock Select Out REFOUT CLKIN CLKSEL EN Reference Voltage 2.5V RC Oscillator 20MHz AGND BGND 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2010, Texas Instruments Incorporated ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. ORDERING INFORMATION (1) (1) PRODUCT PACKAGE-LEAD PACKAGE DESIGNATOR ADS1209 TSSOP-24 PW SPECIFIED TEMPERATURE RANGE -40C to +105C TRANSPORT MEDIA, QUANTITY ORDERING NUMBER ADS1209SPW Tube, 60 ADS1209SPWR Tape and Reel, 2000 For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI web site at www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) Over operating ambient temperature range, unless otherwise noted. ADS1209 UNIT -0.3 to 6 V Supply voltage, AVDD to AGND Supply voltage, BVDD to BGND -0.3 to 6 V Analog input voltage AGND - 0.3 to AVDD + 0.3 V Reference input voltage AGND - 0.3 to AVDD + 0.3 V Digital input voltage BGND - 0.3 to BVDD + 0.3 V Ground voltage difference, AGND to BGND 0.3 V Input current to any pin except supply 10 mA Operating virtual junction temperature range, TJ -40 to +150 C Operating ambient temperature range, TOA ESD ratings, all pins (1) -40 to +125 C Human body model (HBM) JEDEC standard 22, test method A114-C.01 +2000 V Charged device model (CDM) JEDEC standard 22, test method C101 +500 V 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 these or any other conditions beyond those indicated under Recommended Operating Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. DISSIPATION RATINGS (1) PACKAGE TA +25C POWER RATING DERATING FACTOR ABOVE TA = +25C (1) TA = +70C POWER RATING TA = +85C POWER RATING TA = +105C POWER RATING TSSOP-24 1420mW 11.3mW/C 909mW 738mW 511mW This is the inverse of the traditional junction-to-ambient thermal resistance (RqJA). Thermal resistances are not production tested and are for informational purposes only. THERMAL CHARACTERISTICS: TSSOP-24 Over the operating ambient temperature range of -40C to +105C, unless otherwise noted. PARAMETER RqJA Junction-to-air thermal resistance RqJC Junction-to-case thermal resistance PD Device power dissipation (1) 2 TEST CONDITIONS High-K thermal resistance (1) CLKSEL = 0, 5V supply MIN TYP MAX UNIT 88 C/W 26 C/W 100 mW Modeled in accordance with the High-K thermal definitions of EIA/JESD51-3. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 RECOMMENDED OPERATING CONDITIONS PARAMETER MIN NOM MAX UNIT 4.5 5 5.5 V Low-voltage levels 2.7 3.0 3.6 V 5V logic levels 4.5 5 5.5 V 0.5 2.5 2.6 V 0 AVDD V -0.92 x VREF +0.92 x VREF V 24 MHz Supply voltage, AVDD to AGND Supply voltage, BVDD to BGND Reference input voltage, VREF Operating common-mode signal Analog inputs External clock +IN - (-IN) (1) 16 20 Operating ambient temperature range, TOA -40 +125 C Specified ambient temperature range, TA -40 +105 C (1) With reduced accuracy, clock can go from 1MHz up to 33MHz; see Typical Characteristic curves. ELECTRICAL CHARACTERISTICS Over operating ambient temperature range of -40C to +105C, AVDD = 5V, BVDD = 3V, CHx+ = 0.2V to 4.8V, CHx- = 2.5V, VREFIN = VREFOUT = 2.5V (internal), CLKIN = 20MHz, and 16-bit Sinc3 filter with OSR = 256, unless otherwise noted. ADS1209 PARAMETER TEST CONDITIONS RESOLUTION MIN TYP (1) MAX UNIT 16 Bits DC ACCURACY Integral linearity error (2) INL VIN = 2.3VPP -8 3.8 +8 LSB VIN = 2.0VPP -4 1.8 +4 LSB 1 4 LSB Integral linearity match DNL Differential nonlinearity -1 VOS Input offset error -3 +1 LSB 1.5 +3 mV 0.2 2 mV -8 1 +8 mV/C -0.5 0.02 +0.5 % FSR 0.1 0.5 Input offset error match TCVOS Input offset error thermal drift GERR Gain error Referenced to VREFIN Gain error match TCGERR Gain error thermal drift PSRR Power-supply rejection ratio 1.3 4.5V < AVDD < 5.5V % FSR ppm/C 82 dB ANALOG INPUTS FSR Full-scale differential input voltage range (CHx+) - (CHx-); CHx- = 2.5V Specified differential input voltage range (CHx+) - (CHx-); CHx- = 2.5V Absolute operating input voltage range Input capacitance CHx to AGND IIL Input leakage current Clock turned off RID Differential input resistance CID Differential input capacitance Common-mode rejection ratio BW Bandwidth (1) (2) +VREFIN -0.92 x VREF V +0.92 x VREF 0 CI CMRR -VREFIN V AVDD V 1 A 3 -1 pF 100 k 2.5 pF At dc 108 dB VIN = 1.25VPP at 40kHz 117 dB 50 MHz Full-scale sine wave, -3dB All typical values are at TA = +25C. Integral nonlinearity is defined as the maximum deviation of the line through the end points of the specified input range, expressed either as the number of LSBs or as a percent of specified input range (4.6V). Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 3 ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com ELECTRICAL CHARACTERISTICS (continued) Over operating ambient temperature range of -40C to +105C, AVDD = 5V, BVDD = 3V, CHx+ = 0.2V to 4.8V, CHx- = 2.5V, VREFIN = VREFOUT = 2.5V (internal), CLKIN = 20MHz, and 16-bit Sinc3 filter with OSR = 256, unless otherwise noted. ADS1209 PARAMETER TEST CONDITIONS MIN TYP (1) MAX UNIT 8 10 12 MHz 7.8 10 12 MHz 1 20 24 MHz -85 -80 dB SAMPLING DYNAMICS CLKSEL = 1, -40C TA +85C fCLK Internal clock frequency CLKSEL = 1, -40C TA +105C fCLKIN External clock frequency CLKSEL = 0 AC ACCURACY THD Total harmonic distortion VIN = 2.3VPP at 5kHz SFDR Spurious-free dynamic range VIN = 2.3VPP at 5kHz 82 86 dB VIN = 2.3VPP at 5kHz 86 90 dB VIN = 2.0VPP at 5kHz 85 89 dB 80 84 dB 100 dB SNR Signal-to-noise ratio SINAD Signal-to-noise + distortion VIN = 2.3VPP at 5kHz Channel-to-channel isolation VIN = 2.3VPP at 5kHz REFERENCE VOLTAGE OUTPUT VREFOUT Reference output voltage TCVREFOUT Reference output voltage drift Output voltage noise 2.450 2.5 2.550 V 20 ppm/C f = 0.1Hz to 10Hz, CL = 10mF 10 mVRMS f = 10Hz to 10kHz, CL = 10mF 12 mVRMS IREFOUT Output current 10 mA IREFSC Short-circuit current 0.5 mA 100 ms Turn-on settling time To accuracy level of 0.1%, no load REFERENCE VOLTAGE INPUT VREFIN Input voltage RREFIN Input resistance CREFIN Input capacitance IREFIN Input current 0.5 2.5 2.6 V 100 M 5 pF 1 mA V DIGITAL INPUTS Logic family CMOS with Schmitt Trigger VIH High-level input voltage 0.7 x BVDD BVDD + 0.3 VIL Low-level input voltage -0.3 0.3 x BVDD V IIN Input current 50 nA CI Input capacitance VIN = BVDD or BGND 5 pF DIGITAL OUTPUTS Logic family CMOS VOH High-level output voltage BVDD = 4.5V, IOH = -100mA VOL Low-level output voltage BVDD = 4.5V, IOL = +100mA CO Output capacitance CL Load capacitance V 0.5 5 V pF 30 Data format 4 4.44 pF Bit stream Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 ELECTRICAL CHARACTERISTICS (continued) Over operating ambient temperature range of -40C to +105C, AVDD = 5V, BVDD = 3V, CHx+ = 0.2V to 4.8V, CHx- = 2.5V, VREFIN = VREFOUT = 2.5V (internal), CLKIN = 20MHz, and 16-bit Sinc3 filter with OSR = 256, unless otherwise noted. ADS1209 PARAMETER TEST CONDITIONS MIN TYP (1) MAX UNIT DIGITAL INPUTS Logic family LVCMOS VIH High-level input voltage BVDD = 3.6V 2 BVDD + 0.3 V VIL Low-level input voltage BVDD = 2.7V -0.3 0.8 V IIN Input current VIN = BVDD or BGND 50 nA CI Input capacitance 5 pF DIGITAL OUTPUTS Logic family LVCMOS VOH High-level output voltage BVDD = 2.7V, IOH = -100mA VOL Low-level output voltage BVDD = 2.7V, IOL = +100mA CO Output capacitance CL Load capacitance BVDD - 0.2 V 0.2 5 Data format V pF 30 pF Bit stream POWER SUPPLY AVDD Analog supply voltage BVDD Buffer I/O supply voltage AIDD Analog operating supply current BIDD PD Buffer I/O operating supply current Power dissipation 4.5 5.0 5.5 V Low-voltage levels 2.7 3.0 3.6 V 5V logic levels 4.5 5.0 5.5 V CLKSEL = 1 12.2 17 mA CLKSEL = 0 11.8 16 mA 0.9 2 mA BVDD = 3V, CLKOUT = 10MHz BVDD = 5V, CLKOUT = 10MHz 1.3 3 mA CLKSEL = 1, 5V supply 67.5 100.0 mW CLKSEL = 0, 5V supply 65.5 95 mW BLANKSPACE EQUIVALENT INPUT CIRCUITS BVDD AVDD RON 650W C(SAMPLE) 1pF AIN DIN Diode Turn-On Voltage: 0.35V AGND BGND Equivalent Analog Input Circuit Equivalent Digital Input Circuit Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 5 ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com PIN CONFIGURATION PW PACKAGE TSSOP-24 (TOP VIEW) AVDD 1 24 AVDD AGND 2 23 REFOUT REFINA 3 22 AGND NC 4 21 OUTA CHA+ 5 20 OUTB CHA- 6 19 CLKOUT ADS1209 CHB- 7 18 BGND CHB+ 8 17 BVDD NC 9 16 CLKIN REFINB 10 15 CLKSEL AGND 11 14 AGND AVDD 12 13 AVDD PIN DESCRIPTIONS PIN NO. I/O (1) AVDD 1 P Analog power supply; nominal 5V. Decouple to AGND with a 0.1F ceramic capacitor. AGND 2 P Analog ground. Connect to analog ground plane. REFINA 3 AI Reference voltage input for channel A NC 4 NC This pin is not internally connected CHA+ 5 AI Fully differential noninverting analog input channel A CHA- 6 AI Fully differential inverting analog input channel A CHB- 7 AI Fully differential inverting analog input channel B CHB+ 8 AI Fully differential noninverting analog input channel B NC 9 NC This pin is not internally connected REFINB 10 AI Reference voltage input for channel B AGND 11 P Analog ground. Connect to analog ground plane. AVDD 12 P Analog power supply; nominal 5V. Decouple to AGND with a 0.1F ceramic capacitor. AVDD 13 P Analog power supply; nominal 5V. Decouple to AGND with a 0.1F ceramic capacitor. AGND 14 P Analog ground. Connect to analog ground plane. CLKSEL 15 DI Clock select input. When this pin is low, an external clock source at CLKIN is used. When high, the internal RC oscillator is used as clock source. CLKIN 16 DI External clock input. Must be tied to BVDD or BGND, if not used. BVDD 17 P I/O buffer power supply, nominal: 3V. Decouple to BGND with a 0.1F ceramic capacitor BGND 18 P I/O buffer ground. Connect to digital ground plane CLKOUT 19 DO Bit stream clock output OUTB 20 DO Bit stream data output of channel B modulator OUTA 21 DO Bit stream data output of channel A modulator AGND 22 P REFOUT 23 AO AVDD 24 P NAME (1) 6 DESCRIPTION Analog ground. Connect to analog ground plane. Internal reference voltage output, nominal: 2.5V. Decouple to AGND with a 0.1F ceramic capacitor. Analog power supply, nominal: 5V. Decouple to AGND with a 0.1F ceramic capacitor. AI = analog input; AO = analog output; DI = digital input; DO = digital output; P = power supply; NC = not connected. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 PARAMETER MEASUREMENT INFORMATION t2 t1 CLKIN tD1 t3 tD2 t4 CLKOUT tD3 tH1 OUTx Figure 1. ADS1209 Timing Diagram TIMING CHARACTERISTICS (1) Over the recommended operating ambient temperature range of -40C to +105C, AVDD = 5V, and BVDD = 2.7V to 5V, unless otherwise noted. MIN MAX UNIT t1 CLKIN period PARAMETER CLKSEL = 0 TEST CONDITIONS 41.6 1000 ns t2 CLKIN high time CLKSEL = 0 10 t1 - 10 ns CLKSEL = 0 2 x t1 t3 CLKOUT period t4 CLKOUT high time tD1 CLKIN rising edge to CLKOUT falling edge delay CLKSEL = 0 tD2 CLKIN rising edge to CLKOUT rising edge delay CLKSEL = 0 CLKSEL = 1 tD3 CLKOUT rising edge to new data valid delay tH1 Data valid hold time referred to rising CLKOUT edge (1) ns 83 125 ns (t3/2) - 5 (t3/2) + 5 ns 10 ns 10 ns CLKSEL = 0 t2 + 7 ns CLKSEL = 1 (t3/4) + 8 ns CLKSEL = 0 t2 - 3 ns CLKSEL = 1 (t3/4) - 8 ns All input signals are specified with tR = tF = 1.5ns (10% to 90% of BVDD) and timed from a voltage level of (VIL + VIH)/2. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 7 ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com TYPICAL CHARACTERISTICS At AVDD = 5V, BVDD = 3V, CHx+ = +0.2V to +4.8V, CHx- = +2.5V, VREFIN = VREFOUT = 2.5V (internal), CLKSEL = 1, and 16-bit Sinc3 filter, with OSR = 256, unless otherwise noted. INTEGRAL NONLINEARITY MATCH vs INPUT SIGNAL 8 4 6 3 4 2 INL Match (LSB) INL (LSB) INTEGRAL NONLINEARITY vs INPUT SIGNAL VOLTAGE 2 0 -2 -40C +25C +85C +105C -4 -6 -8 -2.5 -2.0 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 Differential Input Voltage (V) 2.0 -1 -40C +25C +85C +105C -3 -4 -2.5 -2.0 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 Differential Input Voltage (V) 2.5 Figure 2. Figure 3. INTEGRAL NONLINEARITY vs TEMPERATURE OFFSET ERROR vs ANALOG SUPPLY VOLTAGE 2.5 2.5 2.0 1.5 Offset Error (mV) 4 2 0 -2 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 -4 -6 -2.5 -3.0 -8 -40 -25 -10 5 20 35 50 65 Temperature (C) 80 95 4.5 110 125 4.6 4.7 4.8 4.9 5.0 5.1 AVDD (V) 5.2 Figure 4. Figure 5. OFFSET ERROR AND MATCH vs TEMPERATURE GAIN ERROR AND MATCH vs TEMPERATURE 0.5 2.5 0.4 Gain Error and Match (%FSR) 3.0 2.0 1.5 1.0 Offset Match 0.5 0 -0.5 -1.0 Offset -1.5 -2.0 5.3 5.4 5.5 0.3 0.2 Gain Match 0.1 0 Gain -0.1 -0.2 -0.3 -0.4 -2.5 -3.0 -0.5 -40 -25 -10 5 20 35 50 65 Temperature (C) 80 95 110 125 -40 -25 -10 Figure 6. 8 2.0 3.0 6 INL (LSB) 0 -2 8 Offset Error and Match (mV) 1 5 20 35 50 65 Temperature (C) 80 95 110 125 Figure 7. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 TYPICAL CHARACTERISTICS (continued) At AVDD = 5V, BVDD = 3V, CHx+ = +0.2V to +4.8V, CHx- = +2.5V, VREFIN = VREFOUT = 2.5V (internal), CLKSEL = 1, and 16-bit Sinc3 filter, with OSR = 256, unless otherwise noted. POWER-SUPPLY REJECTION RATIO vs RIPPLE FREQUENCY COMMON-MODE REJECTION RATIO vs INPUT SIGNAL FREQUENCY 90 120 CMRR (dB) 130 PSRR (dB) 100 80 70 110 100 60 90 100 1k 100 10k 1k 10k Figure 8. Figure 9. INTERNAL CLOCK FREQUENCY ANALOG SUPPLY VOLTAGE INTERNAL CLOCK FREQUENCY vs TEMPERATURE 12.0 12.0 11.5 11.5 11.0 11.0 10.5 10.5 10.0 1M 9.5 10.0 9.5 9.0 9.0 8.5 8.5 8.0 8.0 4.6 4.6 4.7 4.8 4.9 5.0 5.1 AVDD (V) 5.2 5.3 5.4 -40 -25 -10 5.5 5 20 35 50 65 Temperature (C) 80 95 110 125 Figure 10. Figure 11. TOTAL HARMONIC DISTORTION AND SPURIOUS-FREE DYNAMIC RANGE vs INPUT FREQUENCY TOTAL HARMONIC DISTORTION AND SPURIOUS-FREE DYNAMIC RANGE vs TEMPERATURE 96 -80 96 -82 94 -82 94 92 -84 -88 -90 88 THD 86 -92 -94 100 1k 10k 92 THD -86 90 -88 88 -90 84 -92 82 -94 -40 -25 -10 fIN (Hz) Figure 12. SFDR (dB) 90 SFDR (dB) -86 SFDR THD (dB) -80 -84 THD (dB) 100k fIN (Hz) fCLK (MHz) fCLK (MHz) fRIPPLE (Hz) 86 SFDR 84 82 5 20 35 50 65 Temperature (C) 80 95 110 125 Figure 13. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 9 ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com TYPICAL CHARACTERISTICS (continued) At AVDD = 5V, BVDD = 3V, CHx+ = +0.2V to +4.8V, CHx- = +2.5V, VREFIN = VREFOUT = 2.5V (internal), CLKSEL = 1, and 16-bit Sinc3 filter, with OSR = 256, unless otherwise noted. SIGNAL-TO-NOISE RATIO AND SIGNAL-TO-NOISE + DISTORTION vs TEMPERATURE 96 96 94 94 SNR 92 SNR and SINAD (dB) SNR and SINAD (dB) SIGNAL-TO-NOISE RATIO AND SIGNAL-TO-NOISE + DISTORTION vs INPUT FREQUENCY 90 88 86 SINAD 84 82 92 SNR 90 88 86 SINAD 84 82 80 100 80 1k 10k -40 -25 -10 5 20 35 50 65 Temperature (C) FREQUENCY SPECTRUM (4096 Point FFT, fIN = 1kHz, 4.6VPP) FREQUENCY SPECTRUM (4096 Point FFT, fIN = 5kHz, 4.6VPP) 0 0 -20 -20 -40 -40 -60 -80 110 125 -60 -80 -100 -100 -120 -120 -140 0 2 4 6 8 10 12 14 16 18 20 0 2 4 6 Frequency (kHz) 8 10 12 14 16 18 20 Frequency (kHz) Figure 16. Figure 17. INTERNAL REFERENCE VOLTAGE vs TEMPERATURE SUPPLY CURRENT vs TEMPERATURE 2.55 18 2.54 16 2.53 14 2.52 IAVDD, Internal CLK 12 2.51 IDD (mA) VREFOUT (V) 95 Figure 15. -140 2.50 2.49 IAVDD, External CLK 10 8 6 2.48 2.47 4 2.46 2 2.45 0 -40 -25 -10 5 20 35 50 65 Temperature (C) 80 95 110 125 IBVDD -40 -25 -10 Figure 18. 10 80 Figure 14. Magnitude (dB) Magnitude (dB) fIN (Hz) 5 20 35 50 65 Temperature (C) 80 95 110 125 Figure 19. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 GENERAL DESCRIPTION The ADS1209 is a two-channel, second-order, CMOS device with two delta-sigma () modulators, designed for medium- to high-resolution A/D signal conversions from dc to 40kHz (filter response -3dB) if an oversampling ratio (OSR) of 64 is chosen. The output of the converter (OUTx) provides a stream of digital ones and zeros. The time average of this serial output is proportional to the analog input voltage. The modulator shifts the quantization noise to high frequencies. A low-pass digital filter should be used at the output of the modulator. The filter serves two functions. First, it filters out high-frequency noise. Second, the filter converts the 1-bit data stream at a high sampling rate into a higher-bit data word at a lower rate (decimation). An application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA) can be used to implement the digital filter. Alternatively, TI's AMC1210 offers four programmable digital filters that can be used. Figure 20 and Figure 21 show typical application circuits with the ADS1209 connected to an FPGA or ASIC. The overall performance (that is, speed and accuracy) depends on the selection of an appropriate OSR and filter type. A higher OSR produces greater output accuracy while operating at a lower data rate. Alternatively, a lower OSR produces lower output accuracy, but operates at a higher data rate. This system allows flexibility with the digital filter design and is capable of A/D conversion results that have a dynamic range exceeding 86dB with an OSR = 256. 2kW 5kW 5V BVDD AVDD +5V 27W 0.1mF CHA+ OPA2350 0.1nF 5kW CHA- OUTA 2nd-Order DS Modulator OUTB Output Interface Circuit 2kW FPGA or ASIC REFINA CLKOUT 5kW 2kW CHB+ +5V CHB- 5V BVDD 0.1mF REFINB OPA2350 Divider 0.1nF 5kW +3V BGND 27W 0.1mF 2nd-Order DS Modulator 2kW +3V Clock Select CLKIN CLKSEL +5V AVDD +5V Out EN RC Oscillator 20MHz REFOUT Reference Voltage 2.5V 0.1mF AVDD +5V AVDD +5V 0.1mF 0.1mF AVDD AGND AGND AGND AGND 0.1mF 0.1mF +5V OPA336 0.1mF Figure 20. Single-Ended Connection Diagram for the ADS1209 Modulator Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 11 ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com AVDD +5V BVDD 27W R1 CH A+ OPA4354 IN+ CH A- 0.1nF 2nd-Order DS Modulator R2 OUT A Output Interface Circuit OUT B FPGA or ASIC REFIN A CLKOUT +5V CH B+ 27W R1 OPA4354 CH B- 2nd-Order DS Modulator +3V BVDD 0.1mF BGND INREFIN B R2 Divider +5V +3V 27W R1 Clock Select OPA4354 IN+ CLKIN CLKSEL 0.1nF +5V R2 AVDD +5V Out EN +5V RC Oscillator 20MHz 27W R1 OPA4354 IN- REFOUT R2 Reference Voltage 2.5V 0.1mF AVDD +5V AVDD +5V 0.1mF 0.1mF AVDD AGND AGND AGND AGND 0.1mF 0.1mF +5V OPA336 0.1mF Figure 21. Differential Connection Diagram for the ADS1209 Modulator 12 Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 THEORY OF OPERATION The differential analog input of the ADS1209 is implemented with a switched-capacitor circuit. This circuit implements a second-order modulator stage, which digitizes the analog input signal into a 1-bit output stream. The clock source can be internal as well as external. Every analog input signal is continuously sampled by the modulator and compared to a reference voltage that is applied to the REFINx pin. A digital stream that represents the analog input voltage over time appears at the output of the corresponding converter. ANALOG INPUT STAGE Analog Input The topology of the analog inputs of ADS1209 is based on fully differential switched-capacitor architecture. This input stage provides the mechanism to achieve low system noise, high common-mode rejection, and excellent power-supply rejection. BLANKSPACE The input impedance of the analog input depends on the modulator clock frequency (fMOD). Figure 22 shows the basic input structure of one channel of the ADS1209. The relationship between the input impedance of the ADS1209 and the modulator clock frequency is: 100kW ZIN = fMOD/10MHz (1) The input impedance becomes a consideration in designs where the source impedance of the input signal is high. This high impedance may cause degradation in gain, linearity, and THD. The importance of this effect depends on the desired system performance. There are two restrictions on the analog input signals, CHx+ and CHx-. If the input voltage exceeds the range (AGND - 0.3V) to (AVDD + 0.3V), the input current must be limited to 10mA because the input protection diodes on the front end of the converter begin to turn on. In addition, the linearity and noise performance of the device meet the stored specifications only when the differential analog voltage resides within 2.3V (with VREFIN as a midpoint); however, the FSR input voltage is 2.5V. 650W AIN+ 1.2pF 0.4pF High Impedance > 1GW VCM Switching Frequency = CLK 0.4pF 650W 1.2pF AIN- High Impedance > 1GW Figure 22. Input Impedance of the ADS1209 Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 13 ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com Modulator The ADS1209 can be operated in two modes. When CKLSEL = 1, the two modulators operate using the internal clock, which is fixed at 20MHz. When CKLSEL = 0, the modulators operate using an external clock. In both modes, the clock is internally divided by two and functions as the modulator clock. The frequency of the external clock can vary from 1MHz to 24MHz to adjust for the clock requirements of the application. The modulator topology is a second-order, switched-capacitor, modulator, such as the one conceptualized in Figure 23. The analog input voltage and the output of the 1-bit digital-to-analog converter (DAC) are differentiated, providing analog voltages at X2 and X3. The voltages at X2 and X3 are presented to the respective individual integrators. The output of these integrators progresses in a negative or positive direction. When the value of the signal at X4 equals the comparator reference voltage, the output of the comparator switches from low to high, or vice versa, depending on its original state. When the output value of the comparator switches direction, the 1-bit DAC responds on the next clock pulse by changing its analog output voltage at X6, causing the integrators to progress in the opposite direction. The feedback of the modulator to the front end of the integrators forces the value of the integrator output to track the average of the input. DIGITAL OUTPUT A differential input signal of 0V ideally produces a stream of ones and zeros that are high 50% of the time and low 50% of the time. A differential input of +2.3V produces a stream of ones and zeros that are high 92% of the time. A differential input of -2.3V produces a stream of ones and zeros that are high 8% of the time. The input voltage versus the output modulator signal is shown in Figure 24. fCLK X(t) X2 X3 Integrator 1 Integrator 2 X4 DATA fS VREF Comparator X6 DAC Figure 23. Block Diagram of the Second-Order Modulator Modulator Output +FS (Analog Input) -FS (Analog Input) Analog Input Figure 24. Analog Input vs Modulator Output of the ADS1209 14 Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 DIGITAL INTERFACE INTRODUCTION The analog signal connected to the input of the modulator is converted using the clock signal applied to the modulator. The result of the conversion (or modulation) is available on one of the OUTx pins, depending on the modulator. In addition, a common clock output signal (CLKOUT) for both simultaneously-sampling modulators is provided. If CLKSEL = 1, CLKIN must not be left floating, but should tied to BVDD or BGND. This behavior can be adjusted by a cascaded filter structure. For example, the first decimation stage can be a Sinc3 filter with a low OSR, and the second stage a high-order filter. For more information, see application note SBAA094, Combining the ADS1202 with an FPGA Digital Filter for Current Measurement in Motor Control Applications, available for download at www.ti.com. 0 OSR = 32 fDATA = 10MHz/32 = 312.5kHz -3dB: 81.9kHz -10 MODES OF OPERATION The device clock is divided by two before being used as the modulator clock. Therefore, the default clock frequency of the modulator is 10MHz. With a possible external clock range of 1MHz to 24MHz, the modulator operates between 500kHz and 12MHz. FILTER USAGE Gain (dB) -20 The device clock of the ADS1209 is 20MHz by default. The device clock can either be generated by the internal 20MHz RC oscillator or can be provided by an external clock source. For this purpose, the CLKIN pin is provided; it is controlled by the mode setting, CLKSEL. -60 -70 -80 0 H(z) = 1 - z-1 (2) This filter provides the best output performance with a relatively low number of gates required for implementation. For oversampling ratios in the range of 16 to 256, this filter architecture represents a good choice. All the characterizations in this data sheet are done using a Sinc3 filter with an oversampling ratio of OSR = 256 and an output word width of 16 bits. 200 400 600 800 1000 1200 1400 1600 Frequency (kHz) Figure 25. Frequency Response of Sinc3 Filter (OSR = 32) 0 -10 -20 Gain (dB) 3 1 - z-OSR -40 -50 The modulator generates a bitstream. In order to output a digital word equivalent to the analog input voltage, the bitstream must be processed by a digital filter. A simple filter, built with minimal effort and hardware, is the Sinc3 filter shown in Equation 2: -30 -30 -40 -50 -60 100 1k 10k 100k Frequency (Hz) Figure 26. Frequency Response of Sinc3 Filter (OSR = 256) In a Sinc3 filter response (shown in Figure 25 and Figure 26), the location of the first notch occurs at the frequency of output data rate fDATA = fMOD/OSR. The -3dB point is located at half the Nyquist frequency or fDATA/4. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 15 ADS1209 SBAS491 - FEBRUARY 2010 www.ti.com The effective number of bits (ENOB) can be used to compare the performance of A/D converters and modulators. Figure 27 shows the ENOB of the ADS1209 with different filter types. In this data sheet, the ENOB is calculated from the SNR as shown in Equation 3: SNR = 1.76dB + 6.02dB ENOB (3) the modulator clock divided by the OSR. For overcurrent protection, filter types other than Sinc3 may be a better choice. A simple example is a Sinc2 filter. The Sincfast is a modified Sinc2 filter as Equation 4 shows: 2 H(z) = 1 - z-OSR 1-z -1 (1 + z-2 OSR) (4) 16 Figure 28 compares the settling time of different filter types operating with a 10MHz modulator clock. 14 Sinc3 Sinc2 10 10 Sinc 9 8 3 Sincfast 8 6 7 ENOB (Bits) ENOB (Bits) 12 4 2 0 10 100 1000 Sinc 2 6 5 Sinc 4 3 2 OSR 1 Figure 27. Measured ENOB vs OSR 0 0 In motor-control applications, a very fast response time is required for overcurrent detection. There is a constraint between 1ms and 5ms with 3 bits to 7 bits of resolution. The time for full settling depends on the filter order. Therefore, the full settling of the Sinc3 filter requires three data clocks and the Sinc2 filter requires two data clocks. The data clock is equal to 16 2 4 6 Settling Time (ms) 8 10 Figure 28. Measured ENOB vs Settling Time For more information, see application note SBAA094, Combining the ADS1202 with an FPGA Digital Filter for Current Measurement in Motor Control Applications, available for download at www.ti.com. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 ADS1209 www.ti.com SBAS491 - FEBRUARY 2010 LAYOUT CONSIDERATIONS POWER SUPPLIES DECOUPLING An applied external digital filter rejects high-frequency noise. PSRR and CMRR improve at higher frequencies because the digital filter suppresses high-frequency noise. However, the suppression of the filter is not infinite while high-frequency noise continues to influence the conversion result. Good decoupling practices must be used for the ADS1209 and for all components in the design. All decoupling capacitors, specifically the 0.1mF ceramic capacitors, must be placed as close as possible to the pin being decoupled. A 1mF and 10mF capacitor, in parallel with the 0.1mF ceramic capacitor, can be used to decouple AVDD to AGND as well as BVDD to BGND. At least one 0.1mF ceramic capacitor must be used to decouple every AVDD to AGND and BVDD to BGND, as well as for the digital supply on each digital component. Inputs to the ADS1209, such as CHx+, CHx-, and CLKIN, should not be present before the power supply is on. Violating this condition could cause latch-up. If these signals are present before the supply is on, series resistors should be used to limit the input current to a maximum of 10mA. GROUNDING The digital supply sets the I/O voltage for the interface and can be set within a range of 2.7V to 5.5V. Analog and digital sections of the design must be carefully and cleanly partitioned. Each section should have its own ground plane with a connection between them underneath the converter. In cases where both the analog and digital I/O supplies share the same supply source, an RC filter of 10 and 0.1mF can be used to help reduce the noise in the analog supply. For multiple converters, connect the two ground planes as close as possible to each of the converters. Submit Documentation Feedback Copyright (c) 2010, Texas Instruments Incorporated Product Folder Link(s): ADS1209 17 PACKAGE OPTION ADDENDUM www.ti.com 4-Mar-2010 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty ADS1209SPW ACTIVE TSSOP PW 24 ADS1209SPWR ACTIVE TSSOP PW 24 60 Lead/Ball Finish MSL Peak Temp (3) Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR 2000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. 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Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device ADS1209SPWR Package Package Pins Type Drawing TSSOP PW 24 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2000 330.0 16.4 Pack Materials-Page 1 6.95 B0 (mm) K0 (mm) P1 (mm) 8.3 1.6 8.0 W Pin1 (mm) Quadrant 16.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) ADS1209SPWR TSSOP PW 24 2000 367.0 367.0 38.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46C and to discontinue any product or service per JESD48B. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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