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19-1548; Rev 0; 10/99
Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output
General Description
The MAX4372 low-cost, precision, high-side currentsense amplifier is available in a tiny, space-saving SOT23-5 package. Offered in three gain versions (T = +20V/V, F = +50V/V, and H = +100V/V), this device operates from a single +2.7V to +28V supply and consumes only 30A. It features a voltage output that eliminates the need for gain-setting resistors and is ideal for today's notebook computers, cell phones, and other systems where battery/DC current monitoring is critical. High-side current monitoring is especially useful in battery-powered systems since it does not interfere with the ground path of the battery charger. The input common-mode range of 0 to +28V is independent of the supply voltage and ensures that the current-sense feedback remains viable even when connected to a 2cell battery pack in deep discharge. The user can set the full-scale current reading by choosing the device (T, F, or H) with the desired voltage gain and selecting the appropriate external sense resistor. This capability offers a high level of integration and flexibility, resulting in a simple and compact current-sense solution. For higher bandwidth applications, refer to the MAX4173T/F/H data sheet. o 30A Supply Current o +2.7V to +28V Operating Supply o 0.18% Full-Scale Accuracy o Low 1.5 Output Impedance o Three Gain Versions Available +20V/V (MAX4372T) +50V/V (MAX4372F) +100V/V (MAX4372H) o Wide 0 to +28V Common-Mode Range, Independent of Supply Voltage o Available in Space-Saving SOT23-5 Package
Features
o Low-Cost, Compact Current-Sense Solution
MAX4372T/F/H
Ordering Information
PART TEMP. RANGE PIN-PACKAGE TOP MARK ADIU -- ADIV --
MAX4372TEUK-T -40C to +85C 5 SOT23-5 MAX4372TESA -40C to +85C 8 SO MAX4372FEUK-T -40C to +85C 5 SOT23-5 MAX4372FESA -40C to +85C 8 SO
Applications
Power-Management Systems General-System/Board-Level Current Monitoring Notebook Computers Portable/Battery-Powered Systems Smart-Battery Packs/Chargers Cell Phones Precision-Current Sources
MAX4372HEUK-T -40C to +85C 5 SOT23-5 ADIW MAX4372HESA -40C to +85C 8 SO -- Note: Gain values are as follows: +20V/V for the T version, +50V/V for the F version, and +100V/V for the H version.
Typical Operating Circuit
ILOAD GND RS-
Pin Configurations
TOP VIEW
GND
1
5
RS-
VCC 1 N.C. 2 GND 3
8
RS+ N.C. RSN.C.
MAX4372T/F/H
A/D CONVERTER OUT RSENSE VSENSE
OUT
2
MAX4372T/F/H
MAX4372T/F/H
7 6 5
LOAD/ BATTERY
VCC
3
4
RS+
OUT 4
VCC +2.7V TO +28V 0.1F
VCC
RS+ VIN 0 TO 28V
SOT23-5
SO
________________________________________________________________ Maxim Integrated Products
1
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Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output MAX4372T/F/H
ABSOLUTE MAXIMUM RATINGS
VCC, RS+, RS- to GND ...........................................-0.3V to +30V OUT to GND ...........................................................-0.3V to +15V Differential Input Voltage (VRS+ - VRS-) ..............................0.3V Current into Any Pin..........................................................10mA Continuous Power Dissipation (TA = +70C) 5-Pin SOT23 (derate 7.1mW/C above +70C).............571mW 8-Pin SO (derate 5.88mW/C above +70C).................471mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec). ............................+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
(VRS+ = 0 to +28V, VCC = +2.7V to +28V, VSENSE = 0, RLOAD = 1M, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Operating Voltage Range (Note 2) Common-Mode Input Range (Note 3) Common-Mode Rejection Supply Current Leakage Current SYMBOL VCC VCMR CMR ICC IRS+, IRSIRS+ Input Bias Current IRSFull-Scale Sense Voltage (Note 4) Full-Scale Accuracy (Note 5) VSENSE VRS+ > 2V VRS+ > 2V, VSENSE = 5mV VCC = 0 VRS+ > 2V VRS+ 2V VRS+ > 2V VRS+ 2V Gain = +20V/V or +50V/V Gain = +100V/V VSENSE = 100mV, VCC = 12V, VRS+ = 12V, TA = +25C (Note 6) VSENSE = 100mV, VCC = 12V, VRS+ = 12V (Note 6) VSENSE = 100mV, VCC = 28V, VRS+ = 28V (Note 6) VSENSE = 100mV, VCC = 12V, VRS+ = 0.1V (Note 6) VSENSE = 6.25mV, VCC = 12V, VRS+ = 12V (Note 7) OUT Low Voltage OUT High Voltage VCC - VOH VCC = 2.7V IOUT = 10A IOUT = 100A 0.15 1 0.15 2.6 9 0.1 65 0.25 mV V 0 -25 0 -50 150 100 0.18 3 6 7 % 28 CONDITIONS MIN 2.7 0 85 30 0.05 60 1.2 1 2 2 2 mV % A TYP MAX 28 28 UNITS V V dB A A
Total OUT Voltage Error (Note 5)
VCC = 2.7V, IOUT = -500A
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Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output
ELECTRICAL CHARACTERISTICS (continued)
(VRS+ = 0 to +28V, VCC = +2.7V to +28V, VSENSE = 0, RLOAD = 1M, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS VSENSE = 100mV, gain = +20V/V -3dB Bandwidth BW VRS+ = 12V, VCC = 12V, CLOAD = 10pF VSENSE = 100mV, gain = +50V/V VSENSE = 100mV, gain = +100V/V VSENSE = 6.25mV MAX4372T Gain MAX4372F MAX4372H Gain Accuracy VSENSE = 20mV to 100mV Gain = +20V/V, VCC = 12V, VRS+ = 12V, CLOAD = 10pF TA = +25C TA = -40C to +85C VSENSE = 6.25mV to 100mV VSENSE = 100mV to 6.25mV 20 s 20 1000 1.5 75 85 0.5 0.1 pF dB ms ms MIN TYP 275 200 110 50 20 50 100 0.25 2.5 5.5 % V/V MAX UNITS
MAX4372T/F/H
kHz
OUT Settling Time to 1% of Final Value Capacitive Load Stability OUT Output Resistance Power-Supply Rejection Power-Up Time to 1% of Final Value Saturation Recovery Time (Note 8) ROUT PSR
No sustained oscillations VSENSE = 100mV VOUT = 2V, VRS+ > 2V VCC = 12V, VRS+ = 12V, VSENSE = 100mV, CLOAD = 10pF VCC = 12V, VRS+ = 12V, CLOAD = 10pF
Note 1: All devices are 100% production tested at TA = +25C. All temperature limits are guaranteed by design. Note 2: Guaranteed by PSR test. Note 3: Guaranteed by OUT Voltage Error test. Note 4: Output voltage is internally clamped not to exceed 12V. Note 5: Total OUT voltage error is the sum of gain and offset voltage errors. Note 6: Measured at IOUT = -500A (RLOAD = 4k for gain = +20V/V, RLOAD = 10k for gain = +50V/V, RLOAD = 20k for gain = +100V/V). Note 7: +6.25mV = 1/16 of +100mV full-scale voltage (C/16). Note 8: The device will not reverse phase when overdriven.
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Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output MAX4372T/F/H
Typical Operating Characteristics
(VCC = +12V, VRS+ = 12V, VSENSE = 100mV, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4372 toc01
SUPPLY CURRENT vs. TEMPERATURE
MAX4372T toc02
SUPPLY CURRENT vs. COMMON-MODE VOLTAGE
31.5 SUPPLY CURRENT (A) 31.0 30.5 30.0 29.5 29.0 28.5 VSENSE = 5mV 0 4 8 12 16 20 24 28 COMMON-MODE VOLTAGE (V) AV = +20V/V AV = +50V/V AV = +100V/V
MAX4372 toc03
35.0
40 35 SUPPLY CURRENT (A) 30 25 20 15 10
32.0
SUPPLY CURRENT (A)
32.5
AV = +100V/V AV = +50V/V AV = +20V/V
30.0
27.5 VSENSE = 5mV 25.0 0 4 8 12 16 20 24 28
5 0 -40 VSENSE = 5mV -15 10 35 60 85
28.0
SUPPLY VOLTAGE (V)
TEMPERATURE (C)
TOTAL OUTPUT ERROR vs. SUPPLY VOLTAGE
0.4 0.2 OUTPUT ERROR (%) 0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 0 5 10 15 20 25 30 -1.0 0 G = +50V/V G = +20V/V G = +100V/V
MAX4372 toc04
TOTAL OUTPUT ERROR vs. VSENSE
MAX4372T toc05
-45 -50 -55 PSR (dB)
1.0 OUTPUT ERROR (%) AV = +100V/V
0.5
AV = +50V/V
-60 -65 -70 -75
0
AV = +20V/V
-0.5
-80 -85 -90 50 100 150 VSENSE (mV) 200 250 300 100 1k 10k 100k
SUPPLY VOLTAGE (V)
FREQUENCY (Hz)
TOTAL OUTPUT ERROR vs. COMMON-MODE VOLTAGE
MAX4372T toc07
GAIN ACCURACY vs. TEMPERATURE
MAX4372T toc08
TOTAL OUTPUT ERROR vs. TEMPERATURE
0.8 TOTAL OUTPUT ERROR (%) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 AV = +20V/V AV = +100V/V AV = +50V/V
MAX4372T toc09
1.6 1.4 OUTPUT ERROR (%) 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5 G = +20V/V G = +50V/V G = +100V/V
0 -0.1 -0.2 GAIN ACCURACY (%) -0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -0.9 AV = +20V/V AV = +50V/V AV = +100V/V
1.0
10
15
20
25
30
-1.0 -40 -15 10 35 TEMPERATURE (C) 60 85
-40
-15
10
35
60
85
COMMON-MODE VOLTAGE (V)
TEMPERATURE (C)
4
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MAX4372T toc06
0.6
1.5
-40
POWER-SUPPLY REJECTION vs. FREQUENCY
Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output MAX4372T/F/H
Typical Operating Characteristics (continued)
(VCC = +12V, VRS+ = 12V, VSENSE = 100mV, TA = +25C, unless otherwise noted.)
MAX4372T SMALL-SIGNAL TRANSIENT RESPONSE
MAX4372T toc10
MAX4372F SMALL-SIGNAL TRANSIENT RESPONSE
MAX4372T toc11
MAX4372H SMALL-SIGNAL TRANSIENT RESPONSE
MAX4372T toc12
30mV VSENSE 10mV
VSENSE
30mV
VSENSE
30mV
10mV
10mV
600mV VOUT 200mV VOUT
1.5V VOUT 0.5V
3V
1V
20s/div
20s/div
20s/div
MAX4372T LARGE-SIGNAL TRANSIENT RESPONSE
MAX4372T toc13
MAX4372F LARGE-SIGNAL TRANSIENT RESPONSE
MAX4372T toc14
VSENSE
150mV
VSENSE
150mV
50mV 3V VOUT
50mV 7.5V
VOUT 1V 20s/div
2.5V 20s/div
MAX4372H LARGE-SIGNAL TRANSIENT RESPONSE
MAX4372T toc15
SMALL-SIGNAL GAIN vs. FREQUENCY
2
MAX4372T toc16
3 100mV 1 0 GAIN (dB) 0 10V -1 -2 -3 -4 -5 -6 0 -7 -8 1k 10k 100k G = +100V/V
VSENSE
G = +50V/V G = +20V/V
VOUT
20s/div
1M
FREQUENCY (Hz)
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Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output MAX4372T/F/H
Pin Description
PIN SOT23-5 1 2 3 4 5 -- SO 3 4 1 8 6 2, 5, 7 NAME GND OUT VCC RS+ RSN.C. Ground Output Voltage. VOUT is proportional to the magnitude of VSENSE (VRS+ - VRS-). Supply Voltage Power Connection to the External Sense Resistor Load-Side Connection to the External Sense Resistor No Connection. Not internally connected. FUNCTION
_______________Detailed Description
The MAX4372 high-side current-sense amplifier features a 0 to +28V input common-mode range that is independent of supply voltage. This feature allows the monitoring of current flow out of a battery in deep discharge, and also enables high-side current sensing at voltages far in excess of the supply voltage (VCC). Current flows through the sense resistor, generating a sense voltage (Figure 1). Since A1's inverting input is high impedance, the voltage on the negative terminal equals VIN - VSENSE. A1 forces its positive terminal to match its negative terminal; therefore, the voltage across RG1 (VIN - V1-) equals VSENSE. This creates a current to flow through RG1 equal to VSENSE / RG1. The transistor and current mirror amplify the current by a factor of . This makes the current flowing out of the current mirror equal to: IM = VSENSE / RG1 A2's positive terminal presents high impedance, so this current flows through RGD, with the following result: V2+ = RGD * VSENSE / RG1 R1 and R2 set the closed-loop gain for A2, which amplifies V2+, yielding: VOUT = RGD * * VSENSE / RG1 (1 + R2 / R1) The gain of the device equals: VOUT = RGD * (1 + R2 / R1) / RG1 VSENSE
RG1 +2.7V TO +28V VCC V1+ A1 RSV1CURRENT MIRROR IM RG2 RGD RS+
VIN 0 TO +28V
RSENSE ILOAD
VSENSE
TO LOAD
MAX4372T/F/H
OUT A2
V2+
V2GND
R2
R1
Figure 1. Functional Diagram
__________Applications Information
Recommended Component Values
The MAX4372 operates over a wide variety of current ranges with different sense resistors. Table 1 lists common resistor values for typical operation of the MAX4372.
Choosing RSENSE Given the gain and maximum load current, select RSENSE such that VCC - VOUT does not exceed +0.25V and VOUT does not exceed +10V. To measure lower currents more accurately, use a high value for RSENSE. A higher value develops a higher sense voltage, which overcomes offset voltage errors of the internal current amplifier. In applications monitoring very high current, ensure RSENSE is able to dissipate its own I2R losses. If the resistor's rated power dissipation is exceeded, its value may drift or it may fail altogether, causing a differential voltage across the terminals in excess of the absolute maximum ratings.
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Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output
Table 1. Recommended Component Values
FULL-SCALE LOAD CURRENT, ILOAD (A) CURRENT-SENSE RESISTOR, RSENSE (m) GAIN (V/V) 20 0.1 1000 50 100 20 1 100 50 100 20 5 20 50 100 20 10 10 50 100 FULL-SCALE OUTPUT VOLTAGE (FULL-SCALE VSENSE = 100mV), VOUT (V) 2.0 5.0 10.0 2.0 5.0 10.0 2.0 5.0 10.0 2.0 5.0 10.0
MAX4372T/F/H
Using a PC Board Trace as RSENSE If the cost of RSENSE is an issue and accuracy is not critical, use the alternative solution shown in Figure 2. This solution uses copper PC board traces to create a sense resistor. The resistivity of a 0.1-inch-wide trace of 2-ounce copper is about 30m/ft. The resistance temperature coefficient of copper is fairly high (approximately 0.4%/C), so systems that experience a wide temperature variance must compensate for this effect. In addition, self-heating will introduce a nonlinearity error. Do not exceed the maximum power dissipation of the copper trace. For example, the MAX4372T (with a maximum load current of 10A and an RSENSE of 5m) creates a full-scale VSENSE of 50mV that yields a maximum VOUT of 1V. RSENSE, in this case, requires about 2 inches of 0.1inch-wide copper trace.
INPUT 0.3in COPPER
RSENSE 0.1in COPPER
LOAD/BATTERY 0.3in COPPER
VSENSE
RS+
VCC
+2.7V TO +28V
MAX4372T/F/H
RSOUT GND
Chip Information
TRANSISTOR COUNT: 225
Figure 2. Connections Showing Use of PC Board
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Low-Cost, SOT23, Micropower, High-Side Current-Sense Amplifier with Voltage Output MAX4372T/F/H
Package Information
SOT5L.EPS
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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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