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19-2424; Rev 1; 12/02
Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers
General Description
The MAX4238/MAX4239 are low-noise, low-drift, ultrahigh precision amplifiers that offer near-zero DC offset and drift through the use of patented autocorrelating zeroing techniques. This method constantly measures and compensates the input offset, eliminating drift over time and temperature and the effect of 1/f noise. Both devices feature Rail-to-Rail(R) outputs, operate from a single 2.7V to 5.5V supply, and consume only 600A. An active-low shutdown mode decreases supply current to 0.1A. The MAX4238 is unity-gain stable with a gain-bandwidth product of 1MHz, while the decompensated MAX4239 is stable with AV 10V/V and a GBWP of 6.5MHz. The MAX4238/MAX4239 are available in 8-pin narrow SO and 6-pin SOT23 packages. o Ultra-Low, 0.1V Offset Voltage 2.0V (max) at +25C 2.5V (max) at -40C to +85C 3.5V (max) at -40C to +125C o Low 10nV/oC Drift o Specified over the -40oC to +125oC Automotive Temperature Range o Low Noise: 1.5VP-P from DC to 10Hz o 150dB AVOL, 140dB PSRR, 140dB CMRR o High Gain-Bandwidth Product 1MHz (MAX4238) 6.5MHz (MAX4239) o 0.1A Shutdown Mode o Rail-to-Rail Output (RL = 1k) o Low 600A Supply Current o Ground-Sensing Input o Single 2.7V to 5.5V Supply Voltage Range o Available in a Space-Saving 6-Pin SOT23 Package
Features
MAX4238/MAX4239
Applications
Thermocouples Strain Gauges Electronic Scales Medical Instrumentation Instrumentation Amplifiers
Typical Application Circuit
PART
5V
Ordering Information
TEMP RANGE -40oC to +125oC -40oC to +125oC -40oC to +125oC -40oC to +125oC PINPACKAGE 6 SOT23-6 8 SO 6 SOT23-6 8 SO TOP MARK AAZZ -- ABAA --
MAX4238AUT-T
18k 360 STRAIN GUAGE ADC AV = 100 AIN
MAX4238ASA MAX4239AUT-T MAX4239ASA
18k
MAX4238/ MAX4239
Selector Guide
PART MAX4238 MAX4239 MINIMUM STABLE GAIN 1V/V 10V/V GAIN BANDWIDTH (MHz) 1 6.5
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Pin Configurations appear at end of data sheet. 1
________________________________________________________________ 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.
Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers MAX4238/MAX4239
ABSOLUTE MAXIMUM RATINGS
Power-Supply Voltage (VCC to GND).......................................6V All Other Pins .................................(GND - 0.3V) to (VCC + 0.3V) Output Short-Circuit Duration (OUT shorted to VCC or GND) ...............................Continuous Continuous Power Dissipation (TA = +70C) 6-Pin Plastic SOT23 (derate 9.1mW/C above +70C).727mW 8-Pin Plastic SO (derate 5.88mW/C above +70C).....471mW 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
(2.7V V CC 5.5V, V CM = GND = 0V, V OUT = V CC /2, R L = 10k connected to V CC /2, SHDN = V CC , T A = +25 C, unless otherwise noted.)
PARAMETER Input Offset Voltage Long-Term Offset Drift Input Bias Current Input Offset Current Input Noise Voltage Common-Mode Input Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio IB IOS enP-P VCM CMRR PSRR (Note 2) (Note 2) RS = 100, 0.01Hz to 10Hz Inferred from CMRR test -0.1V VCM VCC - 1.3V (Note 1) 2.7V VCC 5.5V (Note 1) 0.05V VOUT VCC - 0.05V (Note 1) Large-Signal Voltage Gain AVOL 0.1V VOUT VCC - 0.1V (Note 1) RL = 10k Output Voltage Swing VOH/VOL RL = 1k Output Short-Circuit Current Output Leakage Current Slew Rate Gain-Bandwidth Product Minimum Stable Closed-Loop Gain GBWP To either supply 0 VOUT VCC, SHDN = GND (Note 2) VCC = 5V, CL = 100pF, VOUT = 2V step RL = 10k, CL = 100pF, measured at f = 100kHz RL = 10k, CL = 100pF, phase margin = 60o MAX4238 MAX4239 MAX4238 MAX4239 MAX4238 MAX4239 RL = 10k RL = 1k VCC - VOH VOL VCC - VOH VOL GND - 0.1 120 120 125 125 140 140 150 dB 145 4 4 35 35 40 0.01 0.35 1.6 1 6.5 1 10 1 10 10 50 50 mA A V/s MHz V/V mV SYMBOL VOS (Note 1) CONDITIONS MIN TYP 0.1 50 1 2 1.5 VCC 1.3 MAX 2 UNITS V nV/1000hr pA pA VP-P V dB dB
2
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Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(2.7V V CC 5.5V, V CM = GND = 0V, V OUT = V CC /2, R L = 10k connected to V CC /2, SHDN = V CC , T A = +25 C, unless otherwise noted.)
PARAMETER Maximum Closed-Loop Gain SYMBOL CONDITIONS RL = 10k, CL = 100pF, phase margin = 60o MAX4238 MAX4239 0.1% (10 bit) Settling Time -1V step 0.025% (12 bit) 0.006% (14 bit) 0.0015% (16 0.1% (10 bit) Overload Recovery Time AV = 10 (Note 4) 0.025% (12 bit) 0.006% (14 bit) 0.0015% (16 0.1% (10 bit) Startup Time AV = 10 0.025% (12 bit) 0.006% (14 bit) 0.0015% (16 Supply Voltage Range Supply Current Shutdown Logic High Shutdown Logic Low Shutdown Input Current VCC ICC VIH VIL 0V V SHDN VCC 0.1 Inferred by PSRR test SHDN = VCC, no load, VCC = 5.5V SHDN = GND, VCC = 5.5V 2.2 0.8 1 2.7 600 0.1 MIN TYP 1000 6700 0.5 1.0 1.7 2.3 3.3 4.1 4.9 5.7 1.8 2.6 3.4 4.3 5.5 850 1 V A V V A ms ms ms MAX UNITS V/V
MAX4238/MAX4239
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3
Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers MAX4238/MAX4239
ELECTRICAL CHARACTERISTICS
(2.7V VCC 5.5V, VCM = GND = 0V, VOUT = VCC/2, RL = 10k connected to VCC/2, SHDN = VCC, TA = -40C to +125C, unless otherwise noted.) (Note 5)
PARAMETER Input Offset Voltage Input Offset Drift Common-Mode Input Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio SYMBOL VOS TCVOS VCM (Note 1) (Note 1) Inferred from CMRR test GND - 0.05V TA = -40C to +85C VCM VCC 1.4V (Note 1) TA = -40C to +125C 2.7V VCC 5.5V (Note 1) RL = 10k, TA = -40C to +85C 0.1V VOUT VCC - 0.1V TA = -40C to +125C (Note 1) Large-Signal Voltage Gain AVOL RL = 1k (Note 1) 0.1V VOUT VCC - 0.1V, TA = -40C to +85C 0.2V VOUT VCC - 0.2V, TA = -40C to +125C VCC - VOH VOL VCC - VOH GND 0.05 115 dB 90 120 125 dB 95 120 dB 80 20 20 100 100 2 2.7 5.5 900 2 2.2 0.7 0V V SHDN VCC 2 A V A V V A mV dB CONDITIONS TA = -40C to +85C TA = -40C to +125C 10 VCC 1.4 MIN TYP MAX 2.5 3.5 UNITS V nV/C V
CMRR PSRR
RL = 10k Output Voltage Swing VOH/VOL RL = 1k
Output Leakage Current Supply Voltage Range Supply Current Shutdown Logic High Shutdown Logic Low Shutdown Input Current VCC ICC VIH VIL
VOL 0V VOUT VCC, SHDN = GND (Note Inferred by PSRR test SHDN = VCC, no load, VCC = 5.5V SHDN = GND, VCC = 5.5V
Note 1: 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 2: 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. Devices are screened during production testing to eliminate defective units. Note 3: Leakage does not include leakage through feedback resistors. Note 4: Overload recovery time is the time required for the device to recover from saturation when the output has been driven to either rail. Note 5: Specifications are 100% tested at TA = +25C, unless otherwise noted. Limits over temperature are guaranteed by design.
4
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Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers
Typical Operating Characteristics
(VCC = 5V, VCM = 0V, RL = 10k connected to VCC/2, SHDN = VCC, TA = +25C, unless otherwise noted.)
OFFSET VOLTAGE vs. COMMON-MODE VOLTAGE
MAX4238/39 toc02 MAX4238/39 toc03
MAX4238/MAX4239
INPUT OFFSET DISTRIBUTION
MAX4238/39 toc01
OFFSET VOLTAGE vs. SUPPLY VOLTAGE
0.4 TA = +125C OFFSET VOLTAGE (V) 0.2 TA = +25C 0 TA = -40C 0.4
50
PERCENTAGE OF UNITS (%)
40
OFFSET VOLTAGE (V)
0.2
TA = +125C
TA = +25C TA = -40C
30
0
20
10
-0.2
-0.2
0 -1.5 -1.2 -0.9 -0.6 -0.3 0 0.3 0.6 0.9 1.2 1.5 OFFSET VOLTAGE (V)
-0.4 2.7 3.4 4.1 4.8 5.5 SUPPLY VOLTAGE (V)
-0.4 0 0.9 1.8 2.7 3.6 COMMON-MODE VOLTAGE (V)
OUTPUT HIGH VOLTAGE vs. OUTPUT SOURCE CURRENT
VOH = VCC - VOUT 0.25 OUTPUT HIGH VOLTAGE (V) 0.20 VCC = 2.7V 0.15 VCC = 5V 0.10 0.05 0 0 5 10 15 20 SOURCE CURRENT (mA)
MAX4238/39 toc04
OUTPUT LOW VOLTAGE vs. OUTPUT SINK CURRENT
MAX4238/39 toc05
MAX4238 GAIN AND PHASE vs. FREQUENCY (TA = +25C)
80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180
MAX4238/39 toc06
0.30
0.35 0.30 OUTPUT LOW VOLTAGE (V) 0.25 VCC = 2.7V 0.20 0.15 0.10 0.05 0 0 5 10 SINK CURRENT (mA) 15 VCC = 5V
GAIN AND PHASE (dB/DEGREES)
VCC = 5V AV = 1000V/V CL = 100pF RL = 10k 0.1k 1k 10k 100k 1M 10M
20
FREQUENCY (Hz)
MAX4238 GAIN AND PHASE vs. FREQUENCY (TA = -40C)
80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180
MAX4238/39 toc07
MAX4238 GAIN AND PHASE vs. FREQUENCY (TA = +125C)
80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180
MAX4238/39 toc08
MAX4239 GAIN AND PHASE vs. FREQUENCY (TA = +25C)
80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180
MAX4238/39 toc09
GAIN AND PHASE (dB/DEGREES)
GAIN AND PHASE (dB/DEGREES)
VCC = 5V AV = 1000V/V CL = 100pF RL = 10k 0.1k 1k 10k 100k 1M 10M
VCC = 5V AV = 1000V/V CL = 100pF RL = 10k 0.1k 1k 10k 100k 1M 10M
GAIN AND PHASE (dB/DEGREES)
VCC = 5V AV = 1000V/V CL = 100pF RL = 10k 0.1k 1k 10k 100k 1M 10M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
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Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers MAX4238/MAX4239
Typical Operating Characteristics (continued)
(VCC = 5V, VCM = 0V, RL = 10k connected to VCC/2, SHDN = VCC, TA = +25C, unless otherwise noted.)
MAX4239 GAIN AND PHASE vs. FREQUENCY (TA = -40C)
80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180
MAX4238/39 toc10
MAX4239 GAIN AND PHASE vs. FREQUENCY (TA = +125C)
80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180
MAX4238/39 toc11
SUPPLY CURRENT vs. SUPPLY VOLTAGE
TA = +125C 500 SUPPLY CURRENT (A) 400 300 200 100 0 TA = -40C TA = +25C
MAx4238/39 toc12
600
GAIN AND PHASE (dB/DEGREES)
VCC = 5V AV = 1000V/V CL = 100pF RL = 10k 0.1k 1k 10k 100k 1M 10M
GAIN AND PHASE (dB/DEGREES)
VCC = 5V AV = 1000V/V CL = 100pF RL = 10k 0.1k 1k 10k 100k 1M 10M
0
1
2
3
4
5
FREQUENCY (Hz)
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX4238/39 toc13
COMMON-MODE REJECTION RATIO vs. FREQUENCY
-20 -40 CMRR (dB) -60 -80 -100 -120 -140 -160 0.01 0.1 1 10 100 1000
MAX4238/39 toc14
MAX4238 LARGE-SIGNAL TRANSIENT RESPONSE
MAX4238/39 toc15
0 -20 -40 PSRR (dB) -60 -80 -100 -120 -140 -160 0.01 0.1 1 10 100
0
IN 1V/div
OUT 1V/div
1000
10s/div AV = 1V/V RL = 2k CL = 100pF
FREQUENCY (kHz)
FREQUENCY (kHz)
MAX4238 SMALL-SIGNAL TRANSIENT RESPONSE
MAX4238/39 toc16
MAX4239 SMALL-SIGNAL TRANSIENT RESPONSE
MAX4238/39 toc17
OVERVOLTAGE RECOVERY TIME
MAX4238/39 toc18
IN 50mV/div
IN 50mV/div
0
IN 50mV/div
OUT 50mV/div OUT 500mV/div 0
OUT 1V/div
10s/div AV = 1V/V RL = 2k CL = 100pF AV = 10V/V RL = 2k CL = 100pF
10s/div AV = 100V/V RL = 10k VCC = 2.5V VEE = -2.5V
400s/div
6
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Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers
Typical Operating Characteristics (continued)
(VCC = 5V, VCM = 0V, RL = 10k connected to VCC/2, SHDN = VCC, TA = +25C, unless otherwise noted.)
DC TO 10Hz NOISE
MAX4238/39 toc19
MAX4238/MAX4239
SHUTDOWN WAVEFORM
MAX4238/39 toc20
SHDN
2V/div
OUT
2V/div
1V/div OUT
1s/div VCC = 2.5V VEE = -2.5V RL = 10k CL = 100pF
10s/div
Pin Description
PIN SOT23 1 2 3 4 5 6 -- SO 6 4 3 2 1 7 5, 8 NAME OUT GND IN+ INSHDN VCC N.C. FUNCTION Amplifier Output Ground Noninverting Input Inverting Input Shutdown Input. Active low shutdown, connect to VCC for normal operation. Positive Power Supply No Connection. Not internally connected.
Detailed Description
The MAX4238/MAX4239 are high-precision amplifiers that have less than 2.5V of input-referred offset and low 1/f noise. These characteristics are achieved through a patented autozeroing technique that samples and cancels the input offset and noise of the amplifier. The pseudorandom clock frequency varies from 10kHz to 15kHz, reducing intermodulation distortion present in chopper-stabilized amplifiers.
capacitor. This type of error is independent of inputsource impedance, or the size of the external gain-setting resistors. Maxim uses a patented design technique to avoid large changes in the voltage on the sampling capacitor to reduce settling time errors. The second error contributor, which is present in both autozero and chopper-type amplifiers, is the charge injection from the switches. The charge injection appears as current spikes at the input, and combined with the impedance seen at the amplifier's input, contributes to input offset voltage. Minimize this feedthrough by reducing the size of the gain-setting resistors and the input-source impedance. A capacitor in parallel with the feedback resistor reduces the amount of clock feedthrough to the output by limiting the closed-loop bandwidth of the device. The design of the MAX4238/MAX4239 minimizes the effects of settling and charge injection to allow specification of an input offset voltage of 0.1V (typ) and less than 2.5V over temperature (-40C to +85C).
1/f Noise
1/f noise, inherent in all semiconductor devices, is inversely proportional to frequency. 1/f noise increases 3dB/octave and dominates amplifier noise at lower frequencies. This noise appears as a constantly changing voltage in series with any signal being measured. The MAX4238/MAX4239 treat 1/f noise as a slow varying offset error, inherently canceling the 1/f noise.
Offset Error Sources
To achieve very low offset, several sources of error common to autozero-type amplifiers need to be considered. The first contributor is the settling of the sampling
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7
Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers MAX4238/MAX4239
Output Overload Recovery
Autozeroing amplifiers typically require a substantial amount of time to recover from an output overload. This is due to the time it takes for the null amplifier to correct the main amplifier to a valid output. The MAX4238/ MAX4239 require only 3.3ms to recover from an output overload (see Electrical Characteristics and Typical Operating Characteristics).
TOP VIEW MAX4238/ MAX4239
SHDN 1 IN- 2 8 7 6 5 N.C. VCC OUT N.C. GND 2 5 SHDN OUT 1
Pin Configurations
MAX4238/ MAX4239
6 VCC
Shutdown
The MAX4238/MAX4239 feature a low-power (0.1A) shutdown mode. When SHDN is pulled low, the clock stops and the device output enters a high-impedance state. Connect SHDN to VCC for normal operation.
IN+
3
GND 4
IN+ 3
4
IN-
SO
SOT23
Applications Information
Minimum and Maximum Gain Configurations
The MAX4238 is a unity-gain stable amplifier with a gainbandwidth product (GBWP) of 1MHz. The MAX4239 is decompensated for a GBWP of 6.5MHz and is stable with a gain of 10V/V. Unlike conventional operational amplifiers, the MAX4238/MAX4239 have a maximum gain specification. To maintain stability, set the gain of the MAX4238 between AV = 1000V/V to 1V/V, and set the gain of the MAX4239 between AV = 6700V/V and 10V/V.
Chip Information
TRANSISTOR COUNT: 821 PROCESS: BiCMOS
ADC Buffer Amplifier
The low offset, fast settling time, and 1/f noise cancellation of the MAX4238/MAX4239 make these devices ideal for ADC buffers. The MAX4238/MAX4239 are well suited for low-speed, high-accuracy applications such as strain gauges (see Typical Application Circuit). Error Budget Example When using the MAX4238/MAX4239 as an ADC buffer, the temperature drift should be taken into account when determining the maximum input signal. With a typical offset drift of 10nV/C, the drift over a 10C range is 100nV. Setting this equal to 1/2LSB in a 16-bit system yields a full-scale range of 13mV. With a single 2.7V supply, an acceptable closed-loop gain is AV = 200. This provides sufficient gain while maintaining headroom.
8
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Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers
Package Information
(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.)
6LSOT.EPS
MAX4238/MAX4239
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9
Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers MAX4238/MAX4239
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.)
SOICN .EPS
INCHES DIM A A1 B C e E H L MAX MIN 0.069 0.053 0.010 0.004 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050
MILLIMETERS MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.25 0.19 1.27 BSC 3.80 4.00 5.80 6.20 0.40 1.27
N
E
H
VARIATIONS:
1
INCHES
MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC
TOP VIEW
DIM D D D
MIN 0.189 0.337 0.386
MAX 0.197 0.344 0.394
D C
A e B A1
0 -8 L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL DOCUMENT CONTROL NO. REV.
21-0041
B
1 1
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) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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