EVALUATION KIT AVAILABLE MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer General Description The MAX4208/MAX4209 ultra-low offset and drift instrumentation amplifiers feature exceptional precision specifications, low power consumption, rail-to-rail output, excellent gainbandwidth product, and buffered REFIN/MODE input in a very small MAX(R) package. These devices use a spreadspectrum, autozeroing technique that constantly measures and corrects the input offset, eliminating drift over time and temperature and the effect of 1/f noise. This technique achieves less than 20V offset voltage, allows ground-sensing capability, provides ultra-low CMOS input bias current and increased common-mode rejection performance. The MAX4208/MAX4209 provide high-impedance inputs optimized for small-signal differential voltages (100mV). All devices provide a gain-bandwidth product of 750kHz. The MAX4208 provides an adjustable gain with two external resistors or unity gain with FB connected to OUT. The MAX4209 is available with a fixed gain of 100V/V with 0.03% (typ) accuracy. Both devices include a reference input (REF) to level-shift the output, allowing for bipolar signals in single-supply applications. In both devices, REFIN/ MODE is an input to a precision unity-gain buffer, which sets the REF voltage to level-shift the output. The internal REF buffer allows the reference to be set by a simple resistive divider or an ADC reference without any loading error. The MAX4208/MAX4209 operate with a 2.85V to 5.5V single-supply voltage and consume only 750A of quiescent current (when the internal buffer is off) and only 1.4A in shutdown mode. These amplifiers also operate with 2.5V dual supplies with REF connected to ground and REFIN/MODE to VSS. The MAX4208/MAX4209 are available in space-saving 8-pin MAX packages and are specified over the automotive operating temperature range (-40C to +125C). Applications Strain-Gauge Amplifiers Industrial Process Control Battery-Powered Medical Equipment Precision Low-Side Current Sense Notebook Computers Differential Voltage Amplification Benefits and Features Spread-Spectrum, Auto-Zero Instrumentation Amplifiers Improve DC Characteristics to Maximize Sensor Performance * Input Offset Voltage: 20V (max) at +25C * 0.25% (max) Gain Error * Low 0.2V/C Offset Voltage Drift * 1pA CMOS Input Bias Current * True Ground Sensing with Rail-to-Rail Output * 750kHz Gain-Bandwidth Product Buffered REF Input for High Accuracy and Bipolar Operation Low Power Operation Supports Remote Sensing and Battery-Powered Applications * 2.85V to 5.5V Single-Supply Operation (or 1.425V to 2.75V Dual Supplies) * 750A Supply Current * 1.4A Shutdown Mode Adjustable (MAX4208) and Fixed Gain of 100 (MAX4209) Provide Design Flexibility Ordering Information PART TEMP RANGE -40C to +125C 8 MAX ADJ MAX4209HAUA+T -40C to +125C 8 MAX 100 +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. Typical Application Circuit 5V R4 VDD/2 IN- R3 IN+ VDD OUT REFIN/MODE REF MAX4208 G = 1 + R2 R1 19-0924; Rev 3; 5/15 GAIN (V/V) MAX4208AUA+T FB MAX is a registered trademark of Maxim Integrated Products, Inc. PINPACKAGE VSS R2 CFB FB R1 REF BUFFER OUT = VDD/2 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Absolute Maximum Ratings VDD to VSS...............................................................-0.3V to +6V All Other Pins................................. (VSS - 0.3V) to (VDD + 0.3V) OUT Short-Circuit Duration........................................Continuous Current Into OUT, VDD, and VSS......................................25mA Current Into Any Other Pin................................................20mA Continuous Power Dissipation (TA = +70C) MAX (derate 4.5mW/C above +70C)......................362mW Operating Temperature Range.......................... -40C to +125C Junction Temperature.......................................................+150C 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. Electrical Characteristics (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = +25C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS MAX4208, G = 100V/V 3 20 MAX4209H, G = 100V/V 3 20 IB -100mV VDIFF +100mV (Note 3) 1 pA Input Offset Current IOS -100mV VDIFF +100mV (Note 3) 1 pA Input Resistance RIN VCM = VDD/2 INPUT DC CHARACTERISTICS Input Offset Voltage Input Bias Current VOS Gain Error Gain Nonlinearity (Note 2) Input Common-Mode Range Input Common-Mode Rejection Ratio www.maximintegrated.com VCM CMRR Differential mode 2 Common mode 2 G -20mV VDIFF +20mV MAX4208, G = 100V/V 0.05 0.25 -20mV VDIFF +20mV MAX4209H, G = 100V/V 0.05 0.25 MAX4208, G = 100V/V 25 150 MAX4209H, G = 100V/V 25 150 Guaranteed by CMRR test VCM = (VSS - 0.1V) to (VDD - 1.30V) V % VSS - 0.1 106 VDD - 1.30 135 ppm V dB Maxim Integrated 2 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Electrical Characteristics (continued) (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Power-Supply Rejection Ratio SYMBOL PSRR CONDITIONS VDD = 2.85V to 5.5V, VREF = VCM = (VSS + 0.5V) MIN TYP 100 125 MAX UNITS dB REFIN/MODE AND REF DC CHARACTERISTICS REFIN/MODE Buffer Input Offset Voltage (Note 2) 10 40 V VSS VSS + 0.05 V REFIN/MODE Input Voltage Low VIL Reference buffer is OFF REFIN/MODE Input Voltage High VIH Shutdown mode VDD 0.2 Reference buffer is ON, guaranteed by REFIN/MODE CMRR test VSS + 0.2 REFIN/MODE Buffered Reference Input Range VREFIN/MODE VDD V VDD 1.3 V REFIN/MODE Buffer Common-Mode Rejection Ratio (VSS + 0.2V) VREF/MODE (VDD - 1.3V) (Note 2) 106 135 dB REFIN/MODE Buffer Power-Supply Rejection Ratio VDD = 2.85V to 5.5V, VREF/MODE = VCM = (VSS + 0.5V) 100 125 dB 1 pA REFIN/MODE Bias Current IREFIN VSS < VREFIN/MODE < VDD (Note 3) REF Common-Mode Range Guaranteed by reference CMRR test (Note 4) VSS REF Common-Mode Rejection Ratio VSS VREF (VDD - 1.30V) (Note 4) 106 REF, FB Bias Current REF Input Current (MAX4209) IREF VDD 1.30 V 135 dB MAX4208 (Note 3) 1 pA VDIFF = 0V (Note 5) 10 nA VDIFF = 100mV (Note 5) 100 A OUTPUT DC CHARACTERISTICS RL = 100k VOH VDD - VOUT Output Voltage Swing (Notes 6 and 7) VOL VOUT - VSS ISC 45 RL = 10k 50 70 RL = 1k 250 325 RL = 100k 30 40 RL = 10k 50 65 250 285 RL = 1k Short-Circuit Current 30 Source +20 Sink -25 Short-Circuit Recovery Time mV mA 0.50 ms MAX4208, G = 1V/V 750 kHz AC CHARACTERISTICS Gain-Bandwidth Product GBW Small-Signal Bandwidth BW MAX4209H, G =100V/V 7.5 kHz Slew Rate (Note 8) SR MAX4208, G = 1V/V, VOUT = 100mV step 80 V/ms www.maximintegrated.com Maxim Integrated 3 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Electrical Characteristics (continued) (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = +25C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL Settling Time Maximum Capacitive Load Input Voltage Noise MIN TYP MAX4208, G = 1V/V 10 MAX4209H 120 MAX UNITS tS To within 0.1% of final value CL No sustained oscillations 200 pF f = 0.1Hz to 10Hz 2.5 VP-P f = 1kHz 140 nV/Hz To within 0.1% of final value 20 ms 20 ms en Power-Up Time Shutdown Enable/Disable Time CONDITIONS tEN, tDIS s POWER SUPPLY Supply Voltage VDD Supply Current IDD Guaranteed by PSRR test 2.85 5.50 VREFIN/MODE = VSS, buffer OFF VDD = 5V 0.75 (VSS + 0.2V) VREFIN/MODE (VDD - 1.3V), buffer ON VDD = 5V 1.40 2.30 1.4 5.0 V 1.30 mA VREFIN/MODE = VDD, shutdown mode A Electrical Characteristics (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = -40C to +125C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS INPUT DC CHARACTERISTICS MAX4208, G = 100V/V Input Offset Voltage VOS MAX4209H, G = 100V/V Input Offset Voltage Temperature Drift (Note 2) Input Bias Current Gain Error www.maximintegrated.com MAX4208, G = 100V/V TCVOS MAX4209H, G = 100V/V TA = +25C to +85C 45 TA = -40C to +125C 60 TA = +25C to +85C 30 TA = -40C to +125C 40 TA = +25C to +85C 0.1 0.45 TA = -40C to +125C 0.1 0.45 TA = +25C to +85C 0.01 0.17 TA = -40C to +125C 0.01 0.17 -100mV VDIFF < +100mV (Note 3) TA = +85C 10 TA = +125C 20 MAX4208, G = 100V/V, -20mV VDIFF +20mV TA = +25C to +85C 0.30 TA = -40C to +125C 0.35 TA = +25C to +85C 0.30 TA = -40C to +125C 0.35 MAX4209H, G = 100V/V, -20mV VDIFF +20mV V V/C pA % Maxim Integrated 4 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Electrical Characteristics (continued) (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = -40C to +125C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL Gain Error Temperature Drift (Note 2) Gain Nonlinearity (Note 2) GNL CONDITIONS MIN TYP MAX -20mV VDIFF +20mV (MAX4208), TA = -40C to +125C G = 100V/V 50 180 -20mV VDIFF +20mV (MAX4209H), TA = -40C to +125C G = 100V/V 50 ppm/C 180 MAX4208, G = 100V/V TA = +25C to +85C 210 TA = -40C to +125C 700 MAX4209H, G = 100V/V TA = +25C to +85C 210 TA = -40C to +125C 700 Guaranteed by CMRR test, TA = -40C to +125C UNITS Input Common-Mode Range VCM Input Common-Mode Rejection Ratio CMRR (VSS - 0.1V) VCM (VDD - 1.6V) TA = +25C to +85C 96 TA = -40C to +125C 90 Power-Supply Rejection Ratio PSRR VDD = 2.85V to 5.5V, VREF = VCM = VSS + 0.5V TA = +25C to +85C 96 TA = -40C to +125C 90 VSS - 0.1 VDD - 1.6 ppm V dB dB REFIN/MODE AND REF DC CHARACTERISTICS REFIN/MODE Buffer Input Offset Voltage REFIN/MODE Buffered Reference Input Range REFIN/MODE Input Voltage Low www.maximintegrated.com VREFIN/MODE VIL TA = +25C to +85C 100 TA = -40C to +125C 100 Reference buffer is ON, guaranteed by REFIN/ MODE CMRR test Reference buffer is OFF VSS + 0.2 V VDD - 1.6 V VSS + 0.05 V Maxim Integrated 5 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Electrical Characteristics (continued) (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = -40C to +125C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL REFIN/MODE Input-Voltage High VIH CONDITIONS MIN MAX4208/MAX4209 in shutdown TYP MAX VDD - 0.2 REFIN/MODE Buffer Common-Mode Rejection Ratio (VSS + 0.2V) VREF (VDD - 1.6V) REF Common-Mode Range (Note 4) Guaranteed by REF CMRR test REF Common-Mode Rejection Ratio VSS VREF (VDD 1.6V) TA = +25C to +85C 96 TA = -40C to +125C 90 REFIN/MODE Buffer Power-Supply Rejection Ratio VDD = 2.85V to 5.5V, VREFIN/MODE = VCM = (VSS + 0.5V) TA = +25C to +85C 96 TA = -40C to +125C 90 TA = +25C to +85C 96 TA = -40C to +125C 90 VSS UNITS V dB VDD - 1.6 V dB dB OUTPUT DC CHARACTERISTICS VOH VDD - VOUT Output Voltage Swing (Note 6) VOL VOUT - VSS RL = 100k 60 RL = 10k 90 RL = 1k 375 RL = 100k 50 RL = 10k 75 RL = 1k 325 mV POWER SUPPLY Supply Voltage Supply Current VDD Guaranteed by PSRR test 2.85 5.50 VREFIN/MODE = VSS, buffer OFF VDD = 5V 1.70 (VSS + 0.2V) VREFIN/MODE (VDD - 1.6V), buffer ON VDD = 5V 3.0 REFIN/MODE = VDD, shutdown mode V mA 10 A Note 1: Specifications are 100% production tested at +25C, unless otherwise noted. Limits over temperature are guaranteed by design. Note 2: Guaranteed by design. Thermocouple and leakage effects preclude measurement of this parameter during production testing. Devices are screened during production testing to eliminate defective units. Note 3: IN+ and IN- are gates to CMOS transistors with typical input bias current of 1pA. CMOS leakage is so small that it is impractical to test and guarantee in production. Max VDIFF is 100mV. Devices are screened during production testing to eliminate defective units. For the MAX4208, when there are no external resistors, the input bias current at FB and REF is 1pA (typ). Note 4: Setting REF to ground (VSS) is allowed if the REF buffer is off. The unity-gain buffer is on when VREFIN/MODE is between 0.15V and (VDD - 1.3V). In this range, VREF = VREFIN/MODE 40V (maximum buffer input offset voltage over temperature). Setting REFIN/MODE to VDD puts the part in shutdown (IDD = 1.4A). Note 5: This is the REF current needed to directly drive the end terminal of the gain-setting resistors when REFIN/MODE is connected to VSS to put the buffer in high-impedance mode. The REF input current is tested at the gain of 100. At gain 10 and 1000, IREF = 100A and 3.4A, respectively at +25C. See the Detailed Description. Note 6: Output swing high (VOH) and output swing low (VOL) are measured only on G = 100 and G = 1000 devices. Devices with G = 1 and G = 10 have output swing high limited by the range of VREF, VCM, and VDIFF (see the Output Swing section). Note 7: Maximum range for VDIFF is from -100mV to +100mV. Note 8: At G = 100V/V and G = 1000V/V, these instrumentation amplifiers are bandwidth limited and not capable of slew-rate-limited dV/dt. www.maximintegrated.com Maxim Integrated 6 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Typical Operating Characteristics (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = +25C, unless otherwise noted.) 15 10 -5 0 5 10 15 20 VOS DRIFT (nV/C) INPUT OFFSET VOLTAGE vs. SUPPLY VOLTAGE INPUT OFFSET VOLTAGE vs. INPUT COMMON-MODE VOLTAGE MAX4208/9 toc03 20 15 -20 TA = -40C 2.5 3.0 3.5 4.0 4.5 5.0 5.5 MAX4208/9 toc05 0 -10 -30 6.0 TA = +85C TA = -20C TA = +25C -20 TA = -40C -1 0 TA = +125C 1 0 0.05 0.10 0.15 0.20 0.25 INPUT OFFSET VOLTAGE vs. REFIN COMMON-MODE (BUFFER ENABLED) 2 3 30 20 TA = -40C TA = -20C TA = +25C 10 0 -10 -20 -30 4 TA = +125C TA = +85C 0 1 2 3 SUPPLY VOLTAGE (V) INPUT COMMON-MODE VOLTAGE (V) REFIN COMMON-MODE (V) LINEARITY ERROR vs. DIFFERENTIAL INPUT VOLTAGE GAIN vs. FREQUENCY COMMON-MODE REJECTION RATIO vs. FREQUENCY 80 60 0 60 4 MAX4208/9 toc09 AV = +100V/V MAX4208/9 toc08 2.0 TA = +125C INPUT OFFSET VOLTAGE (V) MAX4208/9 toc04 -10 20 10 -0.15 -0.10 -0.05 GAIN ACCURACY (%) 30 MAX4208/9 toc07 -20 -40 40 0 -20 40 CMRR (dB) 20 GAIN (dB) INPUT OFFSET VOLTAGE (V) LINEARITY ERROR (ppm) 25 0 -250-200-150-100 -50 0 50 100 150 200 250 300 INPUT OFFSET VOLTAGE (V) 0 20 -40 -60 -80 -100 -60 0 -120 -80 -100 30 MAX4208/9 toc06 -10 0 TA = +85C TA = -20C TA = +25C 10 80 35 10 INPUT OFFSET VOLTAGE (V) -20 -15 20 100 40 5 30 -30 10 AV = +100V/V 45 5 5 0 15 GAIN ACCURACY HISTOGRAM 50 FREQUENCY (%) 20 FREQUENCY (%) 20 OFFSET VOLTAGE DRIFT HISTOGRAM (TA = -20C TO +85C) MAX4208/9 toc02 AV = +100V/V 25 FREQUENCY (%) 25 MAX4208/9 toc01 30 INPUT OFFSET VOLTAGE HISTOGRAM -30 -20 -10 0 10 20 DIFFERENTIAL INPUT VOLTAGE (mV) www.maximintegrated.com 30 -20 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M -140 10 100 1k 10k 100k 1M FREQUENCY (Hz) Maxim Integrated 7 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Typical Operating Characteristics (continued) (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = +25C, unless otherwise noted.) POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX4208 INPUT-REFERRED NOISE MAX4208/9 toc11 MAX4208/9 toc10 0 -20 GAIN (dB) -40 -60 1.2V/div -80 -100 -120 -140 100 10 1k 10k 100k 1M 1s/div FREQUENCY (Hz) 100 0.9 GREY = OUT OF COMMON-MODE RANGE 0.6 0.3 CFB = 10nF CAPACITOR 100 1k 10k 0 100k 600 FREQUENCY (Hz) INTERNAL BUFFER OFF VREFIN/MODE (VSS + 0.05V) 0 400 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 3.0 3.5 4.0 4.5 5.0 5.5 VDD (V) SHUTDOWN CURRENT vs. SUPPLY VOLTAGE 6.0 MAX4208/9 toc15 1.5 VREFIN/MODE = VDD 5.0 IDD (A) 4.0 IDD (mA) 2.5 VREFIN/MODE (V) VREFIN/MODE = VDD/2 TA = +25C TA = -40C 500 SUPPLY CURRENT (BUFFER ON) vs. SUPPLY VOLTAGE 2.0 700 1.0 TA = -40C TA = +25C TA = +125C MAX4208/9 toc16 10 TA = +125C 800 SHUTDOWN MODE 10 1 INTERNAL BUFFER ON VREFIN/MODE (VSS + 0.2V) VREFIN/MODE = VSS 900 IDD (A) IDD (mA) CFB = 1nF CAPACITOR 1.2 1000 MAX4208/9 toc13 WHITE NOISE 140nV/Hz 1000 1.5 MAX4208/9 toc12 INPUT-NOISE DENSITY (nV/Hz) 10,000 SUPPLY CURRENT (BUFFER OFF) vs. SUPPLY VOLTAGE IDD vs. VREFIN/MODE MAX4208/9 toc14 INPUT NOISE vs. FREQUENCY TA = +125C 3.0 TA = +25C 2.0 0.5 1.0 0 2.5 3.0 3.5 4.0 VDD (V) www.maximintegrated.com 4.5 5.0 5.5 0 TA = -40C 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VDD (V) Maxim Integrated 8 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Typical Operating Characteristics (continued) (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = +25C, unless otherwise noted.) LARGE-SIGNAL PULSE RESPONSE TIME LARGE-SIGNAL PULSE RESPONSE TIME MAX4208/9 toc18 MAX4208/9 toc17 VIN+ 5mV/div 2.5V VIN+ 5mV/div 2.5V OUTPUT 50mV/div 2.5V OUTPUT 500mV/div 2.5V AV = 10V/V 100s/div AV = 100V/V 400s/div VIN+ = 10mV STEP VIN- = VREF = (VDD - VSS)/2 VREFIN/MODE = VSS VIN+ = 10mV STEP VIN- = VREF = (VDD - VSS)/2 VREFIN/MODE = VSS LARGE-SIGNAL PULSE RESPONSE TIME MAX4208/9 toc19 VIN+ 1mV/div 2.5V OUTPUT 1V/div 2.5V AV = 1000V/V 400s/div VIN+ = 2mV STEP VIN- = VREF = (VDD - VSS)/2 VREFIN/MODE = VSS www.maximintegrated.com Maxim Integrated 9 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Typical Operating Characteristics (continued) (VDD = 5V, VSS = 0V, VCM = VREF = VDD/2, VREFIN/MODE = VSS, RL = 100k to VDD/2, VDIFF = (VIN+ - VIN-) = 0V, MAX4208 set for G = 100V/V (R1 = 1k, R2 = 99k), TA = +25C, unless otherwise noted.) 0.1% SETTLING TIME vs. GAIN 1000 100 G = 100 160 140 MAX4208/9 toc22 MAX4208/9 toc21 180 SETTLING TIME (s) SETTLING TIME (s) 10,000 SETTLING TIME vs. ACCURACY 120 100 80 60 40 20 10 10 1 100 1000 GAIN (V/V) 0 0.10 0.01 1.00 ACCURACY (%) Pin Description PIN NAME FUNCTION 1 REFIN/MODE Reference/Shutdown Mode Input. Trimode function is as follows: Connect to VDD to put the device in shutdown mode. Connect to an external reference (between VSS + 0.2V and VDD - 1.3V) to buffer the voltage at REFIN/MODE. Using the REF buffer allows the use of a simple resistor-divider or high-impedance external reference to set the OUT level at 0mV IN with minimum error. Connect to VSS to force the internal buffer output into a high-impedance state to allow external direct drive of REF. 2 IN- Negative Differential Input 3 IN+ Positive Differential Input 4 VSS Negative Supply Input. Bypass VSS to ground with a 0.1F capacitor or connect to ground for single-supply operation. 5 REF Output Reference Level. REF sets the OUT voltage for zero differential input. The internal buffer sets the voltage at REF when the voltage at REFIN/MODE is between VSS + 0.2V and VDD - 1.3V. 6 FB 7 OUT Amplifier Output 8 VDD Positive Supply Input. Bypass VDD to ground with a 0.1F capacitor. www.maximintegrated.com Feedback Input. Connect FB to the center tap of an external resistive divider from OUT to REF to set the gain for the MAX4208. MAX4209 FB is internally connected to gain-setting resistors. Connect an optional capacitor, CFB, from OUT to FB to reduce autozero noise. Maxim Integrated 10 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer VDD VDD MAX4208 MAX4209 OUT AMP OUT AMP R2 FB INgm R2 R1 gm REF IN+ +1 FB INgm gm R1 REF IN+ REFIN/MODE +1 SHDN G = 1 + R2 R1 VSS REFIN/MODE SHDN G = 1 + R2 R1 VSS Figure 1. MAX4208 Functional Diagram Figure 2. MAX4209 Functional Diagram Detailed Description cation. The maximum recommended differential input voltage is 100mV. Linearity and accuracy are degraded above that level. The MAX4208/MAX4209 operate with single 2.85V to 5.5V supply voltages or dual 1.425V to 2.75V supplies. The MAX4208/MAX4209 family of instrumentation amplifiers implements a spread-spectrum, autozeroing technique that minimizes the input offset error, drift over time and temperature, and the effect of 1/f noise. Unlike the traditional three-op amp instrumentation amplifier, this technique allows true ground-sensing capability combined with a low input bias current and increased common-mode rejection. The differential input signal is converted to a current by an input transconductance stage. An output transconductance stage converts a portion of the output voltage (equal to the output voltage divided by the gain) into another precision current. These two currents are subtracted and the result is fed to a loop amplifier with sufficient gain to minimize errors (Figures 1 and 2). The MAX4209 has a factory-trimmed gain of 100V/V. The MAX4208 has an adjustable gain, set with an external pair of resistors between OUT, FB, and REF (Figure 1). The MAX4208/MAX4209 have an output reference input (REF) that is connected to an external reference for bipolar operation of the device. For single-supply operation, the range for VREF is 0V to (VDD - 1.3V). Although full output-swing capability and maximum symmetrical dynamic range is obtained at REF = VDD/2, the optimal VREF setting depends on the supply voltage and output-voltage swing needed by the appli- www.maximintegrated.com The MAX4208/MAX4209 have a shutdown feature to reduce the supply current to 1.4A (typ) when REFIN/ MODE is connected to VDD. REF, REFIN/MODE, and Internal REFIN Buffer of the MAX4208/MAX4209 In a single-supply system, bipolar operation of an instrumentation amplifier requires the application of a voltage reference (REF) to set the output voltage level when a zero differential voltage is applied to the input. The output swing is around this reference level, which is usually set to half of the supply voltage for the largest swing and dynamic range. In many instrumentation amplifiers, the gain-setting resistors as well as the RL are connected between OUT and REF. OUT can sink and source current but the need for REF to sink and source current is often overlooked and can lead to significant errors. Therefore, the MAX4208/ MAX4209 include a REFIN buffer, an internal, precision unity-gain buffer on-chip to sink and source the currents needed at REF without loading the reference voltage supplied at REFIN/MODE. Maxim Integrated 11 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Table 1. REFIN/MODE Pin Functions REFIN/MODE VOLTAGE* VDD (typically +5V) STATE OF MAX4208/MAX4209 and REFIN BUFFER The entire IC is in SHDN mode and draws 1.4A of supply current. Between VSS + 200mV and (VDD - 1.3V) The internal REF buffer is activated. REF MUST NOT be fed by any external source. The voltage at REFIN/MODE is transferred to REF within 40FV, max (VOS of the internal REF buffer). VSS (typically ground) The internal REF buffer is OFF with its output in a high-impedance state to allow direct drive of REF (or connection to ground). REF must be directly connected to an external voltage reference capable of sinking and sourcing the load current. *See the Electrical Characteristics table for detailed specifications. In a conventional instrumentation amplifier, a simple method to apply a reference voltage is the use of a voltage-divider to set the REF level (often halfway between ground and VDD). The voltage-divider should be made of higher value resistors to minimize current consumption, but the sinking and sourcing current from the load and gain-setting resistors create a significant commonmode signal at the divider midpoint. The MAX4208/MAX4209 precision REFIN buffer essentially eliminates the error voltage at REF. The REFIN buffer is a unity-gain op amp that has a guaranteed VOS of less than 40V with a CMOS input bias current of only 1pA, to allow setting REFIN with a simple resistive divider with minimum errors. REFIN/MODE is a triple function input (see Table 1). To use the internal REFIN buffer, connect REFIN/MODE to an external reference or a simple resistive divider at any voltage between (VSS + 0.2V) and (VDD - 1.3V). These voltages represent the minimum and maximum for the REFIN buffer's input common-mode range (see the Electrical Characteristics table). To use ground at REF or to use an external low-impedance reference directly at REF without the internal REFIN buffer, connect REFIN/MODE to VSS. This disables the REFIN buffer, dropping the IDD to 750A and puts the REFIN buffer output in a high-impedance state to allow external direct drive of REF. To put the MAX4208/MAX4209 into shutdown and reduce the supply current to less than 5A, drive REFIN/MODE to VDD. Note: When driving REF directly, REFIN/MODE must be at VSS and shutdown mode is NOT available. Input Differential Signal Range The MAX4208/MAX4209 feature a proprietary input structure optimized for small differential signals of up to 100mV. The output of the MAX4208/MAX4209 allows for bipolar input signals. The output voltage is equal to the voltage at REF for zero differential input. The gain accuracy of these devices is laser trimmed to better than 0.1% (typ). www.maximintegrated.com Output Swing The MAX4208/MAX4209 are designed specifically for small input signals (100mV) from sensors, strain gauges, etc. These instrumentation amplifiers are capable of rail-to-rail output-voltage swings; however, depending on the selected gain and REF level, the rail-to-rail output swing may not be required or desired. For example, consider single-supply operation of the MAX4208 in a unity-gain configuration with REF connected to a voltage at half of the supply voltage (VDD/2). In this case, the output-voltage swing would be 100mV around the REF level and would not need to reach either rail. Another example is the MAX4209H (gain internally set to 100) also operating with a single-supply voltage and REF set externally to ground (VSS). REFIN/MODE must also be connected to ground (VSS). In this case, an input voltage of 0 to 10mV differential would ideally drive an output-voltage swing of 0 to 1V. However, the output swing can only get to within 40mV of ground (VSS) (see the VOL specifications in the Electrical Characteristics table). It is recommended that for best accuracy and linearity, the lowest differential input voltage for unipolar operation is usually picked to be a nonzero value (e.g., 0.5mV or more). Another remedy is to use REFIN/MODE of 250mV (see the REFIN/MODE Buffered Reference Input Range in the Electrical Characteristics table), which causes a 0 to 100mV input to start OUT at 250mV and swing to 1.25V, to prevent the output from going into its bottom nonlinear range. An ADC with differential input can be connected between OUT and REF to record the true 0 to 1V swing. Devices with higher gain and bipolar output swing can be configured to approach either rail for maximum dynamic range. However, as the output approaches within VOL or VOH of the supply voltages, the linearity and accuracy degrades, especially under heavy loading. Maxim Integrated 12 MAX4208/MAX4209 Applications Information Setting the Gain (MAX4208) Connect a resistive divider from OUT to REF with the center tap connected to FB to set the gain for the MAX4208 (see the Typical Application Circuit). Calculate the gain using the following formula: R2 GAIN= 1 + R1 Choose a value for R1 1k. Resistor accuracy ratio directly affects gain accuracy. Resistor sum less than 10k should not be used because their loading can slightly affect output accuracy. Input Common Mode vs. Input Differential-Voltage Range Traditional three-op amp instrumentation amplifiers have a defined relationship between the maximum input differential voltage and maximum input common-mode voltage that arises from saturation of intermediate amplifier stages. This correlation is frequently represented as a hexagon graph of input common-mode voltage vs. output voltage for the instrumentation amplifier shown in Figure 3. Application limitations hidden in this graph are: The input common-mode voltage range does not include the negative supply rail, and so no amplification is possible for inputs near ground for single-supply applications. Input differential voltages can be amplified with maximum gain only over a limited range of input commonmode voltages (i.e., range of y-axis for max range of x-axis is limited). If large amplitude common-mode voltages need to be rejected, differential voltages cannot be amplified with a maximum gain possible (i.e., range of x-axis for a maximum range of y-axis is limited). As a consequence, a secondary high-gain amplifier is required to follow the front-end instrumentation amplifier. The indirect current-feedback architecture of the MAX4208/MAX4209 instrumentation amplifiers do not suffer from any of these drawbacks. Figure 4 shows the input common-mode voltage vs. output voltage graph of indirect current-feedback architecture. In contrast to three-op amp instrumentation amplifiers, the MAX4208/MAX4209 features: www.maximintegrated.com Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer The input common-mode voltage range, which includes the negative supply rail and is ideal for singlesupply applications. Input differential voltages that can be amplified with maximum gain over the entire range of input commonmode voltages. Large common-mode voltages that can be rejected at the same time differential voltages are amplified with maximum gain, and therefore, no secondary amplifier is required to follow the front-end instrumentation amplifier. Gain Error Drift Over Temperature Adjustable gain instrumentation amplifiers typically use a single external resistor to set the gain. However, due to differences in temperature drift characteristics between the internal and external resistors, this leads to large gain-accuracy drift over temperature. The MAX4208 is an adjustable gain instrumentation amplifier that uses two external resistors to set its gain. Since both resistors are external to the device, layout and temperature coefficient matching of these parts deliver a significantly more stable gain over operating temperatures. The fixed gain, MAX4209H has both internal resistors for excellent matching and tracking. Use of External Capacitor CFB for Noise Reduction Zero-drift chopper amplifiers include circuitry that continuously compensates the input offset voltage to deliver precision and ultra-low temperature drift characteristics. This self-correction circuitry causes a small additional noise contribution at its operating frequency (a psuedorandom clock around 45kHz for MAX4208/MAX4209). For highbit resolution ADCs, external filtering can significantly attenuate this additional noise. Simply adding a feedback capacitor (CFB) between OUT and FB reduces highfrequency gain, while retaining the excellent precision DC characteristics. Recommended values for CFB are between 1nF and 10nF. Additional anti-aliasing filtering at the output can further reduce this autocorrection noise. Capacitive-Load Stability The MAX4208/MAX4209 are capable of driving capacitive loads up to 200pF. Applications needing higher capacitive drive capability may use an isolation resistor between OUT and the load to reduce ringing on the output signal. However, this reduces the gain accuracy due to the voltage drop across the isolation resistor. Maxim Integrated 13 MAX4208/MAX4209 VCM Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer CLASSIC THREE OP-AMP INA VCM VCC VDD VCM-MAX VCM-MAX MAX4208/MAX4209 3/4 VCC 1/2 VCC VREF = 1/2 VCC VREF = 1/2 VDD 1/4 VCC VOUT ( = GAIN x VDIFF + VREF) 0 VCC/2 VCC VOUT ( = GAIN x VDIFF + VREF) 0 VDD/2 VDD Figure 3. Limited Common Mode vs. Output Voltage of a Three Op-Amp INA Figure 4. Input Common Mode vs. Output Voltage of MAX4208/MAX4209 Includes 0V (GND) Power-Supply Bypass and Layout Low-Side Current-Sense Amplifier Good layout technique optimizes performance by decreasing the amount of stray capacitance at the instrumentation amplifier's gain-setting pins (OUT, FB, and REF). Excess capacitance produces peaking in the amplifier's frequency response. To decrease stray capacitance, minimize trace lengths by placing external components as close as possible to the instrumentation amplifier. Unshielded long traces at the inputs of the instrumentation amplifier degrade the CMRR and pick-up noise. This produces inaccurate output in highgain configurations. Use shielded or coax cables to connect the inputs of the instrumentation amplifier. Since the MAX4208/MAX4209 feature ultra-low input offset voltage, board leakage and thermocouple effects can easily introduce errors in the input offset voltage readings when used with highimpedance signal sources. Minimize board leakage current and thermocouple effects by thoroughly cleaning the board and placing the matching components very close to each other and with appropriate orientation. For best performance, bypass each power supply to ground with a separate 0.1F capacitor. For noisy digital environments, the use of multilayer PCB with separate ground and power-supply planes is recommended. Keep digital signals far away from the sensitive analog inputs. Refer to the MAX4208 or MAX4209 Evaluation Kit data sheets for good layout examples. www.maximintegrated.com The use of indirect current-feedback architecture makes the MAX4208/MAX4209 ideal for low-side current-sensing applications, i.e., where the current in the circuit ground needs to be measured by means of a small sense resistor. In these situations, the input common-mode voltage is allowed to be at or even slightly below ground (VSS - 0.1V). If the currents to be measured are bidirectional, connect REFIN/MODE to VDD/2 to get full dynamic range for each direction. If the currents to be measured are unidirectional, both REFIN/MODE and REF can be tied to GND. However, VOL limitations can limit low-current measurement. If currents need to be measured down to 0A, bias REFIN/MODE to a voltage above 0.2V to activate the internal buffer and to stay above amplifier VOL, and measure both OUT and REF with a differential input ADC. Low-Voltage, High-Side Current-Sense Amplifier Power management is a critical area in high-performance portable devices such as notebook computers. Modern digital processors and ASICs are using smaller transistor geometries to increase speed, reduce size, and also lower their operating core voltages (typically 0.9V to 1.25V). The MAX4208/MAX4209 instrumentation amplifiers can be used as a nearly zero voltage-drop, currentsense amplifier (see Figure 5). Maxim Integrated 14 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer The ultra-low VOS of the MAX4208/MAX4209 allows full-scale VSENSE of only 10mV to 20mV for minimally invasive current sensing using milliohm sense resistors to get high accuracy. Previous methods used the internal resistance of the inductor in the step-down DC-DC converter to measure the current, but the accuracy was only 20% to 30%. Using a full-scale VSENSE of 20mV, a 20V max, VOS error term is less than 0.1% and MAX4209H VSENSE = 10A x 0.002 = 20mV POWER IN RSENSE = 10A x 20mV = 200mW OUT = G x 20mV = 100 x 20mV = 2V gain error is 0.25% max at 100x, so the total accuracy is greatly improved. The 0 to 2V output of MAX4209H can be sent to an ADC for calculation. The adjustable gain of MAX4208, can be set to a gain of 250x using 1k and 249k resistors, to scale up a lower 10mV VSENSE voltage to a larger 2.5V output voltage for wider dynamic range as needed. +3.3V MAX4209H IN+ INREF 1V AT 10A VDD VSS OUT 0.002 +VSENSE- ADC REFIN/MODE ANTI-ALIASING FILTER ASIC Figure 5. MAX4208/MAX4209 Used as Precision Current-Sense Amplifiers for Notebook Computers with VSENSE of 20mV Typical Application Circuit 5V R4 VDD/2 IN- R3 IN+ VDD OUT REFIN/MODE REF FB MAX4208 G = 1 + R2 R1 www.maximintegrated.com VSS R2 CFB FB R1 REF BUFFER OUT = VDD/2 Maxim Integrated 15 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Pin Configuration TOP VIEW REFIN/MODE 1 IN- 2 IN+ 3 + MAX4208 MAX4209 VSS 4 8 VDD 7 OUT 6 FB 5 REF MAX Chip Information PROCESS: BiCMOS www.maximintegrated.com Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 8 MAX U8+1 21-0036 90-0092 Maxim Integrated 16 MAX4208/MAX4209 Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 9/07 Initial release 1 4/09 Removed future products 2 5/14 Removed reference to "automotive transducer applications" from the Applications 1 3 5/15 Added the Benefits and Features section 1 DESCRIPTION -- 1-5, 11, 12, 13 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2015 Maxim Integrated Products, Inc. 17 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX4208AUA+ MAX4208AUA+T MAX4209HAUA+ MAX4209HAUA+T