19-1493; Rev 1; 12/00 KIT ATION EVALU E L B A AVAIL Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer The MAX2685 includes an LNA, LNA bypass switch, downconverter mixer, and local-oscillator (LO) buffer. The LNA has a low noise figure of 1.4dB, a high gain of 15dB, and an input third-order intercept point (IP3) of -4dBm. The mixer has a noise figure of 13dB, a gain of 6dB, and an input IP3 of +7dBm. In addition, an LNA bypass switch allows two levels of gain, reducing power consumption when high gain is not needed. The downconverter mixer has a single-ended RF input port and differential IF output ports. Differential operation of the IF ports offers improved even-order harmonic rejection and increased immunity to noise. An LO buffer allows the LO port to be driven with only -8dBm of LO power. The MAX2685 is offered in a space-saving 16pin QSOP package. Applications Cellular/Cordless Phones Wireless Data Features 800MHz to 1000MHz RF Frequency Range +2.7V to +5.5V Single-Supply Operation Integrated LNA + Mixer + LO Buffer Logic-Controlled LNA Bypass Switch Reduces Supply Current LNA Performance (High/Low Gain) Gain: +15dB/-12dB NF: 1.4dB/12dB Input IP3: -4dBm/+16dBm Mixer Performance (High/Low Gain) Gain: 6dB/4.6dB NF: 13dB/12dB Input IP3: +7dBm/-1.5dBm Supply Current 8.5mA (High Gain) 3.8mA (Low Gain) <0.1A Supply Current in Shutdown Mode 0.8s Receiver Enable Time Ordering Information PART MAX2685EEE TEMP. RANGE -40C to +85C PIN-PACKAGE 16 QSOP 900MHz ISM-Band Radios 868MHz European ISM Band Functional Diagram Pin Configuration LNAOUT MIXIN TOP VIEW LNA GND LNAIN GND GAIN VCC SHDN LO GND 1 16 2 15 3 14 4 13 5 12 6 MAX2685 11 7 10 8 9 QSOP MIXER LNAOUT VCC IFOUT+ LNAIN IFOUT- GND MIXIN LNA BYPASS GAIN GND GND IFOUT+ IFOUT- MAX2685 VCC SHDN GND POWER MANAGEMENT LO BUFFER LO ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX2685 General Description The MAX2685's low-noise amplifier (LNA) and downconverter mixer comprise the major blocks of an RF front-end receiver. Optimized for 900MHz operation, the device's low noise figure, high gain, and high linearity make it ideal for cellular, cordless, and wireless data applications. A low supply current of 8.5mA (high-gain mode) and 3.8mA (low-gain mode) plus a low operating supply voltage range of +2.7V to +5.5V make it suitable for use in 3-cell NiCd or 1-cell lithium-ion (Li+) battery applications. A low-power shutdown mode further extends battery life by reducing supply current below 0.1A. MAX2685 Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer ABSOLUTE MAXIMUM RATINGS VCC to GND ..............................................................-0.3V to +6V LNAIN Input Power (50 source)...................................+10dBm LO Input Power (50 source) ........................................+10dBm MIXIN Input Power (50 source) ...................................+10dBm IFOUT+, IFOUT- to GND ..........................................-0.3V to +6V LNAOUT to GND ......................................................-0.3V to +6V GAIN, SHDN to GND..................................-0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70C) 16-Pin QSOP (derate 8.3mW/C above +70C)............667mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C 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 in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. DC ELECTRICAL CHARACTERISTICS (VCC = +2.7V to +5.5V, V SHDN = +2V, VGAIN = +2V, LNAIN = LNAOUT = MIXIN = LO = unconnected, IFOUT+ = IFOUT- = VCC, TA = -40C to +85C. Typical values are at TA = +25C and VCC = +3V, unless otherwise noted.) PARAMETER CONDITIONS Supply Voltage Range Operating Supply Current MIN TYP 2.7 MAX UNITS 5.5 V GAIN = VCC (Note 1) 8.5 14.1 GAIN = GND (Note 1) 3.8 6.4 0.1 1.0 Shutdown Supply Current SHDN = GND (Note 1) Logic Input Voltage High GAIN, SHDN Logic Input Voltage Low GAIN, SHDN Logic Input Current V SHDN = VGAIN = 0 to 5.5V (Note 1) 2.0 mA A V 0.01 0.5 V 1 A AC ELECTRICAL CHARACTERISTICS (MAX2685 EV kit, VCC = V SHDN = +3V, fLNAIN = fMIXIN = 880MHz, fLO = 960MHz, PLNAIN = -30dBm, PLO = -8dBm, PMIXIN = -25dBm, differential IFOUT operation, Zo = 50, TA = +25C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS 1000 MHz LOW-NOISE AMPLIFIER (LNA) RF Frequency Range (Note 2) LNA Gain LNA Gain Variation over Temperature LNA Noise Figure LNA Input IP3 LNA Input 1dB Compression LNAOUT Port Return Loss 800 GAIN = VCC (Note 1) 13 15 16.2 GAIN = GND (Note 1) -14 -12 -10.3 0.9 1.6 GAIN = VCC, TA = TMIN to TMAX (Note 3) GAIN = VCC 1.4 GAIN = GND 12.2 GAIN = VCC (Note 4) -4.1 GAIN = GND (Note 5) +16.2 GAIN = VCC -18.4 GAIN = VCC -18.6 GAIN = GND -11.3 dB dB dB dBm dBm dB DOWNCONVERTER MIXER RF Frequency Range (Note 2) Mixer Conversion Gain 2 800 1000 GAIN = VCC (Note 1) 4.7 6.1 7.0 GAIN = GND (Note 1) 2.5 4.6 6.0 _______________________________________________________________________________________ MHz dB Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer (MAX2685 EV kit, VCC = V SHDN = +3V, fLNAIN = fMIXIN = 880MHz, fLO = 960MHz, PLNAIN = -30dBm, PLO = -8dBm, PMIXIN = -25dBm, differential IFOUT operation, Zo = 50, TA = +25C, unless otherwise noted.) PARAMETER CONDITIONS Mixer Conversion Gain Variation over Temperature MIN GAIN = VCC, TA = TMIN to TMAX (Note 3) Mixer Noise Figure (SSB) Mixer Input IP3 (Note 6) TYP MAX UNITS 1 2 dB GAIN = VCC 13 GAIN = GND 12.1 GAIN = VCC 7 GAIN = GND -1.5 LO Port Return Loss dB dBm 11 dB 53 dB LO-to-MIXIN Isolation 31 dB LNAOUT-to-MIXIN Isolation 28 dB 0.8 s SHDN = VCC or GND LO-to-LNAIN Isolation OVERALL SYSTEM Receiver Enable Time (Note 7) Note 1: Performance at temperatures greater than or equal to +25C are guaranteed by production test; performance at temperatures less than +25C are guaranteed by design and characterization. Note 2: This is the recommended operating frequency range. Note 3: Maximum and minimum limits are guaranteed by design and device characterization and are not production tested. Note 4: Two tones at 880MHz and 880.1MHz, -30dBm per tone. Note 5: Two tones at 880MHz and 880.1MHz, -10dBm per tone. Note 6: Two tones at 880MHz and 880.1MHz, -25dBm per tone. Note 7: Time from SHDN = high, until the cascaded receive gain is within 1dB of its final value. Measured with 47pF blocking capacitors on LNAIN and LNAOUT. Matching network removed from IFOUT output. Typical Operating Characteristics (MAX2685 EV kit, VCC = V SHDN = +3V, fLNAIN = fMIXIN = 880MHz, fLO = 960MHz, PLNAIN = -30dBm, PLO = -8dBm, PMIXIN = -25dBm, differential IFOUT operation, Zo = 50, TA = +25C, unless otherwise noted.) SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE TA = +25C 7 6 GAIN = HIGH TA = -40C TA = +85C 5 4 3 GAIN = LOW TA = +25C 2 TA = -40C 8 TA = +85C 5 4 3 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 0 -5 2 -10 TA = -40C 0 0 5 TA = +25C 1 1 TA = +85C TA = +25C 10 7 6 TA = -40C GAIN = HIGH 15 GAIN (dB) SUPPLY CURRENT (mA) 8 SHDN = GND 9 LNA GAIN vs. SUPPLY VOLTAGE 20 MAX2685 toc02 TA = +85C 10 SHUTDOWN SUPPLY CURRENT (nA) 9 MAX2685 toc01 10 MAX2685 toc03 SUPPLY CURRENT vs. SUPPLY VOLTAGE 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 TA = +25C T = -40C A GAIN = LOW TA = +85C -15 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 3 MAX2685 AC ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (MAX2685 EV kit, VCC = V SHDN = +3V, fLNAIN = fMIXIN = 880MHz, fLO = 960MHz, PLNAIN = -30dBm, PLO = -8dBm, PMIXIN = -25dBm, differential IFOUT operation, Zo = 50, TA = +25C, unless otherwise noted.) 0 -5 -10 -5 TA = -40C 3.0 3.5 4.0 4.5 5.0 5.5 LNA REVERSE ISOLATION vs. FREQUENCY GAIN = LOW -15 -20 -25 -30 -35 GAIN = HIGH 0 MAX2685 toc08 -7 -8 GAIN = HIGH -9 -10 -11 -12 -2 GAIN = LOW -4 -6 -8 GAIN = LOW -10 -12 -14 -13 -16 -14 -18 GAIN = HIGH -20 800 840 880 920 960 1000 800 840 880 FREQUENCY (MHz) FREQUENCY (MHz) LNA S11 vs. FREQUENCY (800MHz to 1000MHz UNMATCHED) MAX2685 toc10 TA = -40C GAIN = HIGH 5.0 HI LO LOW GAIN = TA = -40C TA = +85C 4.5 1000 TA = +85C 6 4 2 TA = +85C TA = +25C GAIN = HIGH TA = -40C 0 TA = +25C -2 GAIN = LOW -4 TA = +25C 4.0 -6 TA = +85C 3.5 800 8 INPUT IP3 (dBm) GAIN (dB) GAIN = LOW 1000 800 10 6.0 5.5 960 MIXER INPUT IP3 vs. SUPPLY VOLTAGE MIXER GAIN vs. SUPPLY VOLTAGE 7.0 6.5 920 FREQUENCY (MHz) TA = +25C 4 MAX2685 toc06 LNA OUTPUT RETURN LOSS vs. FREQUENCY -15 -40 800 825 850 875 900 925 950 975 1000 1000 GAIN = HIGH 1.0 870 880 890 900 910 920 930 940 950 960 LNA INPUT RETURN LOSS vs. FREQUENCY -6 INPUT RETURN LOSS (dB) -10 1.3 FREQUENCY (MHz) -5 MAX2685 toc07 -5 1.4 FREQUENCY (MHz) SUPPLY VOLTAGE (V) 0 1.5 1.1 -20 800 825 850 875 900 925 950 975 1000 OUTPUT RETURN LOSS (dB) 2.5 1.6 1.2 GAIN = LOW -15 -10 1.7 MAX2685 toc09 TA = +85C MAX2685 toc11 GAIN = HIGH 5 MAX2685 toc12 5 TA = +25C 1.8 NOISE FIGURE (dB) GAIN (dB) 10 0 1.9 10 TA = +85C TA = -40C GAIN = HIGH 15 2.0 MAX2685 toc05 15 INPUT IP3 (dBm) 20 MAX2685 toc04 TA = +25C GAIN = LOW LNA NOISE FIGURE vs. FREQUENCY LNA GAIN vs. FREQUENCY LNA INPUT IP3 vs. SUPPLY VOLTAGE 20 REVERSE ISOLATION (dB) MAX2685 Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer TA = -40C -8 3.0 -10 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5.0 5.5 Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer MIXER GAIN vs. IF FREQUENCY MIXER GAIN vs. LO POWER GAIN = HIGH 5 0 -2 GAIN (dB) GAIN (dB) GAIN = HIGH 6 2 GAIN = LOW -4 -6 GAIN = LOW 4 3 2 -8 BANDWIDTH DETERMINED BY DIFFERENTIAL-TO-SINGLE-ENDED CONVERTER CIRCUIT -10 -12 60 70 80 90 1 0 100 -15 -10 IF FREQUENCY (MHz) 13.0 GAIN = LOW 12.5 12.0 GAIN = HIGH 11.5 -6 -7 RETURN LOSS (dB) 13.5 MAX2685 toc16 14.0 0 LO PORT RETURN LOSS vs. FREQUENCY -5 MAX2685 toc15 14.5 -5 LO POWER (dBm) MIXER NOISE FIGURE vs. LO POWER 15.0 NOISE FIGURE (dB) MAX2685 toc14 6 4 7 MAX2685 toc13 8 -8 -9 -10 -11 -12 11.0 -13 10.5 -14 -15 10.0 -15 -10 -5 LO POWER (dBm) 0 750 800 850 900 950 1000 1050 1100 FREQUENCY (MHz) _______________________________________________________________________________________ 5 MAX2685 Typical Operating Characteristics (continued) (MAX2685 EV kit, VCC = V SHDN = +3V, fLNAIN = fMIXIN = 880MHz, fLO = 960MHz, PLNAIN = -30dBm, PLO = -8dBm, PMIXIN = -25dBm, differential IFOUT operation, Zo = 50, TA = +25C, unless otherwise noted.) Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer MAX2685 Pin Description PIN NAME FUNCTION 1, 3, 8, 11, 12, 14 GND 2 LNAIN RF Input to LNA and LNA Bypass Switch. Requires an external matching network and a series DC-blocking capacitor. 4 GAIN Gain Control Logic-Level Input. Drive high to enable the LNA, open the LNA bypass switch, and increase the receiver's gain. Drive low to disable the LNA, close the LNA bypass switch, and reduce the receiver's gain. 5, 15 VCC Supply Voltage. Bypass VCC to GND at each pin with a 47pF capacitor as close to the pin as possible. 6 SHDN 7 LO Local-Oscillator Input to Downconverter Mixer. Requires a series DC-blocking capacitor and an impedance-setting resistor (typically 75 to ground). 9 IFOUT- Inverting Side to Downconverter Mixer's Differential Open-Collector IF Output. Requires a pull-up inductor to VCC for proper biasing, as well as a matching network to ensure optimum output power. 10 IFOUT+ Noninverting Side of Downconverter Mixer's Differential Open-Collector IF Output. Requires a pull-up inductor to VCC for proper biasing, as well as a matching network to ensure optimum output power. 13 MIXIN 16 LNAOUT Ground. Connect to ground plane with a low-inductance connection. Shutdown Control Logic-Level Input. Drive high or connect to VCC for normal operation. Drive low to place the device in low-power shutdown mode. RF Input to Downconverter Mixer. Requires an external matching network and series DC-blocking capacitor. LNA Output. Internally matched to 50. LNAOUT has an internal blocking capacitor. 300pF 1 LNA INPUT 880MHz 0.1F 12nH 2 3 GND LNAOUT VCC LNAIN 15 VCC 47pF GND GND GAIN MIXIN 14 MIXER INPUT 880MHz 300pF GAINCONTROL INPUT 4 5 VCC VCC 47pF 6 SHUTDOWN INPUT SHDN 13 3.3pF MAX2685 GND GND 6pF 12 11 12pF 330pF LO INPUT 960MHz LNA OUTPUT 16 7 IFOUT+ 10 LO R* 75 8 GND IFOUT- 820nH 680nH IF OUTPUT 80MHz VCC 9 1000pF 6pF *OPTIONAL FOR BROADBAND MATCH. Figure 1. Typical Operating Circuit 6 _______________________________________________________________________________________ Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer The MAX2685 consists of five major components: a low-noise amplifier (LNA), an LNA bypass switch, a downconverter mixer, a local-oscillator (LO) buffer, and a power-management block. When a large input signal is present, enable the LNA bypass function to increase linearity and reduce supply current. Set GAIN low to enable the LNA bypass function. Low-Noise Amplifier (LNA) The LNA is a wideband, single-ended cascode amplifier that operates over a wide range of frequencies. The input of the LNA (LNAIN) requires an appropriate matching network and a DC-blocking capacitor. The typical operating circuit shown in Figure 1 is optimized for frequencies around 880MHz, requiring only a 0.1F capacitor in series with a 12nH inductor. See Table 1 for the LNA "S" parameters for matching to other frequencies. The output of the LNA (LNAOUT) is internally biased to VCC. It is internally matched to 50 and incorporates an internal DC-blocking capacitor. Receive Mixer The downconverter mixer is a wideband, single-balanced design with a low noise figure and high linearity. The RF signal at the MIXIN port is mixed with the signal at the LO port, and is downconverted to an IF frequency at the differential IF port. RF Input The MIXIN input requires a simple external matching network and a series DC-blocking capacitor. See Figure 1 for a matching network example, optimized for 880MHz operation. Table 2 lists mixer "S" parameters for matching to other frequencies. Table 1. LNA Typical S-Parameters (VCC = +3V, TA = +25C) FREQUENCY (MHz) |S11| MAG S11 PHASE (degrees) |S21| |S12| MAG S21 PHASE (degrees) |S22| MAG S12 PHASE (degrees) MAG S22 PHASE (degrees) High-Gain Mode (GAIN = VCC) 800 0.761 -64.5 4.98 177.9 0.018 -163.7 0.376 -107.3 840 0.753 -68.6 5.06 167.2 0.022 -167.1 0.264 -107.0 880 0.747 -73.2 5.07 156.6 0.026 -171.3 0.172 -94.6 920 0.733 -78.0 4.91 146.6 0.030 -175.7 0.149 -62.9 960 0.719 -82.8 4.68 137.7 0.035 178.0 0.200 -42.4 1000 0.693 -87.5 4.40 130.3 0.039 171.0 0.263 -38.8 Low-Gain Mode (GAIN = GND) 800 0.625 -45.6 0.188 73.0 0.191 71.9 0.483 -91.3 840 0.621 -48.1 0.195 65.5 0.198 64.2 0.423 -91.3 880 0.619 -50.9 0.199 58.1 0.201 56.7 0.370 -89.9 920 0.611 -53.3 0.200 51.6 0.202 50.3 0.337 -86.1 960 0.608 -55.5 0.200 46.1 0.201 44.7 0.322 -80.9 1000 0.607 -57.5 0.200 41.2 0.200 40.0 0.317 -76.7 _______________________________________________________________________________________ 7 MAX2685 LNA Bypass Switch and Gain Control Detailed Description MAX2685 Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer Table 2. Mixer Typical S-Parameters (VCC = +3V, TA = +25C) RF FREQUENCY (MHz) S11 MAG |S11| PHASE (degrees) IF FREQUENCY (MHz) MAG (IFOUT+ Port Only) S22 PHASE (IFOUT+ Port Only) (degrees) |S22| High-Gain Mode (GAIN = VCC) 800 0.355 152.7 10 0.996 -0.4 840 0.352 153.7 40 0.994 -1.8 880 0.351 154.5 80 0.993 -3.2 920 0.349 155.8 110 0.989 -4.2 960 0.352 156.2 170 0.988 -6.2 1000 0.353 156.9 240 0.983 -8.0 800 0.275 142.8 10 0.996 -0.5 840 0.268 144.1 40 0.995 -1.8 880 0.262 145.5 80 0.993 -3.2 920 0.255 147.7 110 0.989 -4.2 960 0.254 149.0 170 0.987 -6.2 1000 0.245 156.9 240 0.982 -7.9 Low-Gain Mode (GAIN = GND) 8 _______________________________________________________________________________________ Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer IF Output Port The mixer's downconverted output appears on the differential IFOUT+ and IFOUT- pins. The differential output can be converted to a single-ended output, as shown in the MAX2685 evaluation kit (EV kit). Refer to the Detailed Description in the MAX2685 EV kit data sheet. Applications Information Layout Considerations A properly designed PC board is an essential part of any RF/microwave circuit. Note the IC's high-frequency inputs and outputs, and be sure to decouple the DC supply and control pins. For power-supply traces and connections, a star topology works well. Each VCC node in the circuit has its own path to the central VCC node and a decoupling capacitor that provides a low impedance at the RF frequency of interest. The central VCC also has a large decoupling capacitor. This provides good isolation between the different sections of the MAX2685. Shutdown Drive SHDN low to disable all device functions and place the MAX2685 in low-power shutdown mode. Drive SHDN high or connect it to VCC to enable all device functions. Chip Information TRANSISTOR COUNT: 295 _______________________________________________________________________________________ 9 MAX2685 Local-Oscillator Input The LO port is the high-impedance input of the localoscillator buffer. It requires a series DC-blocking capacitor and a shunt resistor to ground to set the input impedance. See the Typical Operating Characteristics for a graph of LO Port Return Loss vs. Frequency. Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer QSOP.EPS MAX2685 Package Information Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.