View MAX4209_4113057.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-0924; Rev 0; 9/07
KIT ATION EVALU E AILABL AV
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer
General Description Features
Ultra-Low 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 Buffered REF Input for High Accuracy and Bipolar Operation 2.85V to 5.5V Single-Supply Operation (or 1.425V to 2.75V Dual Supplies) 750A Supply Current 1.4A Shutdown Mode 750kHz Gain-Bandwidth Product Operate Over the -40C to +125C Automotive Temperature Range Tiny 8-Pin MAX Package
MAX4208/MAX4209
The MAX4208/MAX4209 ultra-low offset and drift instrumentation amplifiers feature exceptional precision specifications, low power consumption, rail-to-rail output, excellent gain-bandwidth product, and buffered REFIN/MODE input in a very small MAX(R) package. These devices use a patented spread-spectrum, 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 groundsensing 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 in fixed gains of 10V/V, 100V/V, or 1000V/V (suffixed T, H, and K) with 0.03% (typ) accuracy. Both devices include a reference input (REF) to level-shift the output, allowing for bipolar signals in singlesupply 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 V SS . The MAX4208/MAX4209 are available in space-saving 8-pin MAX packages and are specified over the automotive operating temperature range (-40C to +125C).
US
Ordering Information
PART MAX4208AUA+T MAX4209TAUA+T* MAX4209HAUA+T MAX4209KAUA+T* TEMP RANGE PINPACKAGE GAIN (V/V) ADJ 10 100 1000
-40C to +125C 8 MAX-8 -40C to +125C 8 MAX-8 -40C to +125C 8 MAX-8 -40C to +125C 8 MAX-8
Note: All 8-pin MAX packages have package code U8-1. +Denotes a lead-free package. *Future product--contact factory for availability.
Typical Application Circuit
5V
Patent #6,847,257.
Applications
Automotive Transducer Applications Strain-Gauge Amplifiers Industrial Process Control Battery-Powered Medical Equipment Precision Low-Side Current Sense Notebook Computers Differential Voltage Amplification
R4 VDD/2 R3 ININ+ REFIN/MODE REF FB VSS VDD OUT
R2
CFB
MAX4208 G = 1 + R2 R1
FB R1 REF BUFFER OUT = VDD/2
MAX is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
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) 8-Pin 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 INPUT DC CHARACTERISTICS MAX4208, G = 100V/V Input Offset Voltage VOS MAX4209T, G = 10V/V MAX4209H, G = 100V/V MAX4209K, G = 1000V/V Input Bias Current Input Offset Current Input Resistance IB IOS RIN -100mV VDIFF +100mV (Note 3) -100mV VDIFF +100mV (Note 3) VCM = VDD/2 Differential mode Common mode 3 3 3 3 1 1 2 2 0.05 0.05 % 0.05 0.10 25 25 25 50 VSS 0.1 106 135 VDD 1.30 V dB 150 150 ppm 0.25 0.25 20 20 20 20 pA pA G V SYMBOL CONDITIONS MIN TYP MAX UNITS
-20mV VDIFF +20mV MAX4208, G = 100V/V -100mV VDIFF +100mV MAX4209T, G = 10V/V Gain Error -20mV VDIFF +20mV MAX4209H, G = 100V/V -2mV VDIFF +2mV MAX4209K, G = 1000V/V MAX4208, G = 100V/V Gain Nonlinearity (Note 2) MAX4209T, G = 10V/V MAX4209H, G = 100V/V MAX4209K, G = 1000V/V Input Common-Mode Range Input Common-Mode Rejection Ratio VCM CMRR Guaranteed by CMRR test VCM = (VSS - 0.1V) to (VDD - 1.30V)
2
_______________________________________________________________________________________
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 100 TYP 125 MAX UNITS dB
MAX4208/MAX4209
REFIN/MODE AND REF DC CHARACTERISTICS REFIN/MODE Buffer Input Offset Voltage REFIN/MODE Input-Voltage Low REFIN/MODE Input-Voltage High REFIN/MODE Buffered Reference Input Range REFIN/MODE Buffer Common-Mode Rejection Ratio REFIN/MODE Buffer Power-Supply Rejection Ratio REFIN/MODE Bias Current REF Common-Mode Range REF Common-Mode Rejection Ratio REF, FB Bias Current REF Input Current (MAX4209) OUTPUT DC CHARACTERISTICS RL = 100k VOH Output-Voltage Swing (Notes 6 and 7) VOL VOUT - VSS Source Sink VDD - VOUT RL = 10k RL = 1k RL = 100k RL = 10k RL = 1k Short-Circuit Current Short-Circuit Recovery Time AC CHARACTERISTICS Gain-Bandwidth Product Small-Signal Bandwidth GBW BW MAX4208, G = 1V/V MAX4209T, G =10V/V MAX4209H, G =100V/V MAX4209K, G =1000V/V Slew Rate (Note 8) SR MAX4208, G = 1V/V, VOUT = 100mV step MAX4209T, G =10V/V, VOUT = 1V step 750 75 7.5 0.75 80 55 V/ms kHz kHz ISC 30 50 250 30 50 250 +20 -25 0.50 45 70 325 40 65 285 mA ms mV IREF IREFIN VIL VIH VREFIN/MODE (Note 2) Reference buffer is OFF Shutdown mode Reference buffer is ON, guaranteed by REFIN/MODE CMRR test (VSS + 0.2V) VREF/MODE (VDD - 1.3V) (Note 2) VDD = 2.85V to 5.5V, VREF/MODE = VCM = (VSS + 0.5V) VSS < VREFIN/MODE < VDD (Note 3) Guaranteed by reference CMRR test (Note 4) VSS VREF (VDD - 1.30V) (Note 4) MAX4208 (Note 3) VDIFF = 0V (Note 5) VDIFF = 100mV (Note 5) VSS 106 135 1 10 100 VDD 0.2 VSS + 0.2 106 100 135 125 1 VDD 1.30 10 VSS VDD VDD 1.3 40 VSS + 0.05 V V V V dB dB pA V dB pA nA A
_______________________________________________________________________________________
3
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
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 CONDITIONS MAX4208, G = 1V/V Settling Time tS To within 0.1% of final value MAX4209T MAX4209H MAX4209K Maximum Capacitive Load Input-Voltage Noise Power-Up Time Shutdown Enable/Disable Time POWER SUPPLY Supply Voltage VDD Guaranteed by PSRR test VREFIN/MODE = VSS, buffer OFF Supply Current IDD (VSS + 0.2V) VREFIN/MODE (VDD - 1.3V), buffer ON VDD = 5V VDD = 5V 2.85 0.75 1.40 1.4 5.50 1.30 mA 2.30 5.0 A V tEN, tDIS CL en No sustained oscillations f = 0.1Hz to 10Hz f = 1kHz To within 0.1% of final value MIN TYP 10 15 120 1100 200 2.5 140 20 20 pF VP-P nV/Hz ms ms s MAX UNITS
VREFIN/MODE = VDD, shutdown mode
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 INPUT DC CHARACTERISTICS MAX4208, G = 100V/V Input Offset Voltage VOS MAX4209H, G = 100V/V MAX4208, G = 100V/V TCVOS MAX4209H, G = 100V/V (Note 3) -100mV VDIFF < +100mV MAX4208, G = 100V/V, -20mV VDIFF +20mV MAX4209H, G = 100V/V, -20mV VDIFF +20mV TA = +25C to +85C TA = -40C to +125C TA = +25C to +85C TA = -40C to +125C TA = +25C to +85C TA = -40C to +125C TA = +25C to +85C TA = -40C to +125C TA = +85C TA = +125C TA = +25C to +85C TA = -40C to +125C TA = +25C to +85C TA = -40C to +125C 0.1 0.1 0.01 0.01 10 20 0.30 0.35 0.30 0.35 % 45 60 30 40 0.45 0.45 0.17 0.17 pA V/C V SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Offset Voltage Temperature Drift (Note 2)
Input Bias Current
Gain Error
4
_______________________________________________________________________________________
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 CONDITIONS -20mV VDIFF +20mV (MAX4208), G = 100V/V -100mV VDIFF +100mV (MAX4209T), G = 10V/V -20mV VDIFF +20mV (MAX4209H), G = 100V/V -2mV VDIFF +2mV (MAX4209K), G = 1000V/V MAX4208, G = 100V/V GNL MAX4209H, G = 100V/V VCM TA = -40C to +125C TA = -40C to +125C TA = -40C to +125C TA = -40C to +125C MIN TYP 50 MAX 180 UNITS
MAX4208/MAX4209
50 ppm/C 50 180
Gain Error Temperature Drift (Note 2)
100 210 700 210 700 VSS 0.1 96 90 96 90 dB dB VDD 1.6 V ppm
TA = +25C to +85C TA = -40C to +125C TA = +25C to +85C TA = -40C to +125C
Gain Nonlinearity (Note 2)
Input Common-Mode Range Input Common-Mode Rejection Ratio
Guaranteed by CMRR test, TA = -40C to +125C (VSS - 0.1V) VCM (VDD - 1.6V) VDD = 2.85V to 5.5V, VREF = VCM = VSS + 0.5V TA = +25C to +85C TA = -40C to +125C TA = +25C to +85C TA = -40C to +125C
CMRR
Power-Supply Rejection Ratio
PSRR
REFIN/MODE AND REF DC CHARACTERISTICS REFIN/MODE Buffer Input Offset Voltage REFIN/MODE Buffered Reference Input Range REFIN/MODE Input-Voltage Low VREFIN/MODE VIL TA = +25C to +85C TA = -40C to +125C Reference buffer is ON, guaranteed by REFIN/MODE CMRR test Reference buffer is OFF VSS + 0.2 100 100 VDD 1.6 VSS + 0.05 V V V
_______________________________________________________________________________________
5
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
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 REFIN/MODE Input-Voltage High REFIN/MODE Buffer Common-Mode Rejection Ratio REF Common-Mode Range (Note 4) REF Common-Mode Rejection Ratio REFIN/MODE Buffer Power-Supply Rejection Ratio OUTPUT DC CHARACTERISTICS RL = 100k VOH Output-Voltage Swing (Note 6) VOL POWER SUPPLY Supply Voltage VDD Guaranteed by PSRR test VREFIN/MODE = VSS, buffer OFF Supply Current (VSS + 0.2V) VREFIN/MODE (VDD - 1.6V), buffer ON VDD = 5V VDD = 5V 2.85 5.50 1.70 mA 3.0 10 A V VOUT - VSS VDD - VOUT RL = 10k RL = 1k RL = 100k RL = 10k RL = 1k 60 90 375 50 75 325 mV SYMBOL VIH CONDITIONS MAX4208/MAX4209 in shutdown (VSS + 0.2V) VREF (VDD - 1.6V) TA = +25C to +85C TA = -40C to +125C MIN VDD 0.2 96 dB 90 VSS 96 90 96 dB TA = -40C to +125C 90 VDD 1.6 V dB TYP MAX UNITS V
Guaranteed by REF CMRR test VSS VREF (VDD 1.6V) VDD = 2.85V to 5.5V, VREFIN/MODE = VCM = (VSS + 0.5V) TA = +25C to +85C TA = -40C to +125C TA = +25C to +85C
REFIN/MODE = VDD, shutdown mode
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, I REF = 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.
6
_______________________________________________________________________________________
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
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.)
OFFSET VOLTAGE DRIFT HISTOGRAM (TA = -20C TO +85C)
MAX4208/9 toc01 MAX4208/9 toc02
INPUT OFFSET VOLTAGE HISTOGRAM
30 25 FREQUENCY (%) 20 15 10 5 0 -20 -15 -10 -5 0 5 10 15 20 INPUT OFFSET VOLTAGE (V) 25 AV = +100V/V
GAIN ACCURACY HISTOGRAM
45 40 FREQUENCY (%) 35 30 25 20 15 AV = +100V/V
MAX4208/9 toc03
50
20 FREQUENCY (%)
15
10
5
10 5
0 -250-200-150-100 -50 0 50 100 150 200 250 300 VOS DRIFT (nV/C)
0 -0.15 -0.10 -0.05 0 0.05 0.10 0.15 0.20 0.25 GAIN ACCURACY (%)
INPUT OFFSET VOLTAGE vs. SUPPLY VOLTAGE
MAX4208/9 toc04
INPUT OFFSET VOLTAGE vs. INPUT COMMON-MODE VOLTAGE
MAX4208/9 toc05
INPUT OFFSET VOLTAGE vs. REFIN COMMON-MODE (BUFFER ENABLED)
MAX4208/9 toc06
30 20 10 0 -10 -20 -30 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 TA = -40C TA = +125C TA = +85C TA = -20C TA = +25C
30 20 10 0 -10 -20 -30 TA = -40C TA = +125C TA = +85C TA = -20C TA = +25C
30 20 10 0 -10 -20 -30 TA = +125C TA = +25C TA = -40C TA = -20C
INPUT OFFSET VOLTAGE (V)
INPUT OFFSET VOLTAGE (V)
INPUT OFFSET VOLTAGE (V)
TA = +85C
6.0
-1
0
1
2
3
4
0
1
2
3
4
SUPPLY VOLTAGE (V)
INPUT COMMON-MODE VOLTAGE (V)
REFIN COMMON-MODE (V)
LINEARITY ERROR vs. DIFFERENTIAL INPUT VOLTAGE
MAX4208/9 toc07
GAIN vs. FREQUENCY
MAX4208/9 toc08
COMMON-MODE REJECTION RATIO vs. FREQUENCY
MAX4208/9 toc09
100 80 60 LINEARITY ERROR (ppm) 40 AV = +100V/V
80
0 -20 -40 CMRR (dB)
60
0 -20 -40 -60 -80 -100 -30 -20 -10 0 10 20 30 DIFFERENTIAL INPUT VOLTAGE (mV)
GAIN (dB)
20
40
-60 -80 -100
20
0 -120 -20 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) -140 10 100 1k 10k 100k 1M FREQUENCY (Hz)
_______________________________________________________________________________________
7
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
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
MAX4208/9 toc10
MAX4208 INPUT-REFERRED NOISE
MAX4208/9 toc11
0 -20 -40 GAIN (dB) -60
1.2V/div -80 -100 -120 -140 10 100 1k 10k 100k 1M 1s/div FREQUENCY (Hz)
INPUT NOISE vs. FREQUENCY
MAX4208/9 toc12
IDD vs. VREFIN/MODE
MAX4208/9 toc13
SUPPLY CURRENT (BUFFER OFF) vs. SUPPLY VOLTAGE
VREFIN/MODE = VSS TA = +125C
MAX4208/9 toc14
10,000 WHITE NOISE 140nV/Hz CFB = 1nF CAPACITOR 100
1.5
1000 900 800 IDD (A) 700 600 500 400
INPUT-NOISE DENSITY (nV/Hz)
1.2 INTERNAL BUFFER ON VREFIN/MODE (VSS + 0.2V) IDD (mA) 0.9 GREY = OUT OF COMMON-MODE RANGE SHUTDOWN MODE
1000
0.6
TA = -40C
TA = +25C
10 CFB = 10nF CAPACITOR 1 10 100 1k FREQUENCY (Hz) 10k 100k
0.3
INTERNAL BUFFER OFF VREFIN/MODE (VSS + 0.05V) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VREFIN/MODE (V)
0
2.5
3.0
3.5
4.0 VDD (V)
4.5
5.0
5.5
SUPPLY CURRENT (BUFFER ON) vs. SUPPLY VOLTAGE
MAX4208/9 toc15
SHUTDOWN CURRENT vs. SUPPLY VOLTAGE
VREFIN/MODE = VDD
MAX4208/9 toc16
2.0
VREFIN/MODE = VDD/2
6.0 5.0 4.0
1.5 IDD (mA) IDD (A) TA = +125C TA = +25C
1.0 TA = -40C TA = +25C TA = +125C
3.0 2.0
0.5 1.0 0 2.5 3.0 3.5 4.0 VDD (V) 4.5 5.0 5.5 0 2.5 3.0 3.5 4.0 VDD (V) 4.5 5.0 5.5 TA = -40C
8
_______________________________________________________________________________________
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
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
MAX4208/9 toc17
LARGE-SIGNAL PULSE RESPONSE TIME
MAX4208/9 toc18
VIN+ 5mV/div
2.5V
VIN+ 5mV/div
2.5V
OUTPUT 50mV/div
2.5V 100s/div AV = 10V/V VIN+ = 10mV STEP VIN- = VREF = (VDD - VSS)/2 VREFIN/MODE = VSS
OUTPUT 500mV/div
2.5V 400s/div AV = 100V/V 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 400s/div AV = 1000V/V VIN+ = 2mV STEP VIN- = VREF = (VDD - VSS)/2 VREFIN/MODE = VSS
_______________________________________________________________________________________
9
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
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
MAX4208/9 toc21
SETTLING TIME vs. ACCURACY
G = 100 160 140 SETTLING TIME (s) 120 100 80 60 40 20
MAX4208/9 toc22
10,000
180
SETTLING TIME (s)
1000
100
10 1 10 GAIN (V/V) 100 1000
0 0.01 0.10 ACCURACY (%) 1.00
Pin Description
PIN NAME FUNCTION 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 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. INNegative Differential Input IN+ VSS REF Positive Differential Input Negative Supply Input. Bypass VSS to ground with a 0.1F capacitor or connect to ground for single-supply operation. 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. 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. Amplifier Output Positive Supply Input. Bypass VDD to ground with a 0.1F capacitor.
1
2 3 4 5
6 7 8
FB OUT VDD
10
______________________________________________________________________________________
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
VDD VDD
MAX4208
AMP OUT R2 INgm IN+ gm FB R1 REF IN+ IN-
MAX4209
AMP R2 FB gm gm R1 REF OUT
+1
REFIN/MODE
+1
REFIN/MODE
SHDN G = 1 + R2 R1
SHDN
G = 1 + R2 R1
VSS
VSS
Figure 1. MAX4208 Functional Diagram
Figure 2. MAX4209 Functional Diagram
Detailed Description
The MAX4208/MAX4209 family of instrumentation amplifiers implements a patented 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 factory-trimmed gains of 10V/V, 100V/V, and 1000V/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 application. 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 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.
11
______________________________________________________________________________________
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
Table 1. REFIN/MODE Pin Functions
REFIN/MODE VOLTAGE* VDD (typically +5V) Between VSS + 200mV and (VDD - 1.3V) VSS (typically ground) STATE OF MAX4208/MAX4209 and REFIN BUFFER The entire IC is in SHDN mode and draws 1.4A of supply current. 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 40V, max (VOS of the internal REF buffer). 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 V SS . 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.
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 railto-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 MAX4209T (gain internally set to 10) also operating with a single-supply voltage and REF set externally to ground (VSS). REFIN/MODE must also be connected to ground (V SS). In this case, an input voltage of 0 to 100mV differential would ideally drive an output-voltage swing of 0 to 1V. However, the output swing can only get to within 40mV of ground (V SS ) (see the V OL 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 (a millivolt 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.
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).
12
______________________________________________________________________________________
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer
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. * The input common-mode voltage range, which includes the negative supply rail and is ideal for single-supply applications. * Input differential voltages that can be amplified with maximum gain over the entire range of input common-mode 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.
MAX4208/MAX4209
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, MAX4209T/H/K has both internal resistors for excellent matching and tracking.
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 commonmode 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 singlesupply applications. * Input differential voltages can be amplified with maximum gain only over a limited range of input common-mode 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:
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 high-bit resolution ADCs, external filtering can significantly attenuate this additional noise. Simply adding a feedback capacitor (C FB ) between OUT and FB reduces high-frequency 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.
______________________________________________________________________________________
13
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
VCM CLASSIC THREE OP-AMP INA VCM MAX4208/MAX4209
VCC VCM-MAX 3/4 VCC
VDD VCM-MAX
1/2 VCC
VREF = 1/2 VCC VREF = 1/2 VDD
1/4 VCC VOUT ( = GAIN x VDIFF + VREF) 0 VCC/2 0 VCC VDD/2 VDD VOUT ( = GAIN x VDIFF + VREF)
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
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 high-impedance 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.
Low-Side Current-Sense Amplifier
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, current-sense amplifier (see Figure 5).
14
______________________________________________________________________________________
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer
The ultra-low VOS of the MAX4208/MAX4209 allows fullscale 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, V OS error term is less than 0.1% and MAX4209H 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.
MAX4208/MAX4209
VSENSE = 10A x 0.002 = 20mV POWER IN RSENSE = 10A x 20mV = 200mW OUT = G x 20mV = 100 x 20mV = 2V
+3.3V
MAX4209H
IN+ VDD INREF VSS OUT REFIN/MODE ADC
1V AT 10A
0.002 +VSENSEASIC
ANTI-ALIASING FILTER
Figure 5. MAX4208/MAX4209 Used as Precision Current-Sense Amplifiers for Notebook Computers with VSENSE of 20mV
Typical Application Circuit
5V
R4 VDD/2 R3 ININ+ REFIN/MODE REF FB VSS VDD OUT
R2
CFB
MAX4208 G = 1 + R2 R1
FB R1 REF BUFFER OUT = VDD/2
______________________________________________________________________________________
15
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer MAX4208/MAX4209
Pin Configuration
TOP VIEW +
REFIN/MODE 1 ININ+ 2 3 8 7 VDD OUT FB REF
MAX4208 MAX4209
6 5
VSS 4
MAX
Chip Information
TRANSISTOR COUNT: 2335 PROCESS: BiCMOS
16
______________________________________________________________________________________
Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
8LUMAXD.EPS
MAX4208/MAX4209
4X S
8
8
INCHES DIM A A1 A2 b MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
O0.500.1
E
H
0.60.1
c D e E H L
1
1
0.60.1
S
D
BOTTOM VIEW
0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
c e b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
Note: MAX4208AUA/MAX4209_AUA use Package Code U8-1.
1 1
J
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17 (c) 2007 Maxim Integrated Products
SPRINGER
is a registered trademark of Maxim Integrated Products, Inc.

▲Up To Search▲

Price & Availability of MAX4209

	To Download MAX4209 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .