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19-1434; Rev 5; 4/11
Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier
General Description
The MAX4173 low-cost, precision, high-side currentsense amplifier is available in a tiny SOT23-6 package. It features a voltage output that eliminates the need for gain-setting resistors and it is ideal for today's notebook computers, cell phones, and other systems where 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 battery in deep discharge. The MAX4173's wide 1.7MHz bandwidth makes it suitable for use inside battery charger control loops. The combination of three gain versions and a userselectable external sense resistor sets the full-scale current reading. This feature offers a high level of integration, resulting in a simple and compact currentsense solution. The MAX4173 operates from a single +3V to +28V supply, typically draws only 420A of supply current over the extended operating temperature range (-40C to +85C), and is offered in the space-saving SOT23 package.
Features
o Low-Cost, Compact Current-Sense Solution o High Accuracy +2V to +28V Common-Mode Range, Functional Down to 0V, Independent of Supply Voltage o Three Gain Versions Available +20V/V (MAX4173T) +50V/V (MAX4173F) +100V/V (MAX4173H) o 0.5% Full-Scale Accuracy o 3mV Input Offset Voltage (MAX4173T) o Wide 1.7MHz Bandwidth (MAX4173T) o 420A Supply Current o Available in Space-Saving SOT23 Package
MAX4173T/F/H
Typical Operating Circuit
0 TO +28V VSENSE RSENSE +3V TO +28V 0.1F MAX4173T/F/H A/D CONVERTER OUT GND LOAD/ BATTERY RS+ VCC RSILOAD
Applications
Notebook Computers Portable/Battery-Powered Systems Smart Battery Packs/Chargers Cell Phones Power-Management Systems General System/Board-Level Current Monitoring PA Bias Control Precision Current Sources
Ordering Information
PART MAX4173TEUT+T MAX4173TESA+ MAX4173FEUT+T MAX4173FESA+ MAX4173HEUT+T MAX4173HESA+ GAIN (V/V) 20 20 50 50 100 100 TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 6 SOT23 8 SO 6 SOT23 8 SO 6 SOT23 8 SO SOT TOP MARK AABN -- AABO -- AABP --
+Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel.
Pin Configurations appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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.
Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier MAX4173T/F/H
ABSOLUTE MAXIMUM RATINGS
VCC, RS+, RS- to GND .......................................... -0.3V to +30V OUT to GND .............................................. -0.3V to (VCC + 0.3V) Output Short-Circuit to VCC or GND ......................... Continuous Differential Input Voltage (VRS+ - VRS-) ............................. 0.3V Current into Any Pin......................................................... 20mA Continuous Power Dissipation (TA = +70C) 8-Pin SO (derate 5.88mW/C above +70C)............... 471mW SOT23-6 (derate 8.7mW/C above +70C)................. 696mW Operating Temperature Range .......................... -40C to +85C Storage Temperature Range ............................ -65C to +150C Lead Temperature (soldering, 10s) ................................ +300C Soldering Temperature (reflow) ...................................... +260C
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 = +3V to +28V, VSENSE = 0V, TA = TMIN to TMAX, RLOAD = unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Operating Voltage Range Common-Mode Input Range Common-Mode Rejection Supply Current Leakage Current SYMBOL VCC VCMR CMR ICC IRS+, IRSIRS+ Input Bias Current IRSFull-Scale Sense Voltage VSENSE (Note 2) VRS+ > +2.0V VRS+ > +2.0V, VCC > 12V VCC = 0V, VRS+ = 28V VRS+ > +2.0V VRS+ +2.0V VRS+ > +2.0V VRS+ +2.0V VSENSE = VRS+ - VRSVSENSE = +100mV, VCC = +12V, VRS+ = +12V VSENSE = +100mV, VCC = +12V, VRS+ = +12V, TA = +25C Total OUT Voltage Error (Note 3) VSENSE = +100mV, VCC = +28V, VRS+ = +28V VSENSE = +100mV, VCC = +12V, VRS+ = +0.1V VCC = +12V, VRS+ = +12V, VSENSE = +6.25mV (Note 4) MAX4173T, VCC = +3.0V, VRS+ = 28V, VSENSE = 250mV Out High Voltage (Note 5) (VCC - VOH) MAX4173F, VCC = +7.5V, VRS+ = 28V, VSENSE = 250mV MAX4173H, VCC = +15V, VRS+ = 28V, VSENSE = 250mV OUT Low Voltage VOL MAX4173TEUT, TA = +25C VCC = +5V, VRS+ = 0.89V, TA = -40C to +85C VSENSE = 0mV 0 -350 0 -700 150 0.5 0.5 0.5 -9 7.5 0.8 0.8 0.8 1.2 1.2 1.2 1.2 5 mV 40 V 5.75 3.25 5.75 24 % CONDITIONS Guaranteed by PSR test MIN 3 0 90 0.42 0.3 1.0 3 50 50 100 100 mV A TYP MAX 28 28 UNITS V V dB mA A
2
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier MAX4173T/F/H
ELECTRICAL CHARACTERISTICS (continued)
(VRS+ = 0 to +28V, VCC = +3V to +28V, VSENSE = 0V, TA = TMIN to TMAX, RLOAD = unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MAX4173T, VSENSE = +100mV VRS+ = +12V, VCC = +12V, CLOAD = 5pF MAX4173F, VSENSE = +100mV MAX4173H, VSENSE = +100mV VSENSE = +6.25mV (Note 4) MAX4173T Gain AV MAX4173F MAX4173H AV Gain Accuracy AV Input Offset Voltage (Note 6) MAX4173H VSENSE = +10mV to +100mV, VCC = VRS+ = 12V MAX4173TEUT, VRS+ = 12V VCC = +12V, VRS+ = 12V, CLOAD = 5pF ROUT MAX4173T, VSENSE = 80mV, VRS+ +2V Power-Supply Rejection Power-Up Time to 1% of Final Value Saturation Recovery Time PSR MAX4173F, VSENSE = 32mV, VRS+ +2V MAX4173H, VSENSE = 16mV, VRS+ +2V VSENSE = +100mV, CLOAD = 5pF VCC = +12V, VRS+ = 12V (Note 7) 60 60 60 TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C VSENSE = +6.25mV to +100mV VSENSE = +100mV to +6.25mV 400 ns 800 12 84 91 95 10 10 s s dB k 0.3 0.5 2.5 4.0 3 5 mV MAX4173T/F VSENSE = +10mV to +150mV, VCC = VRS+ = 12V TA = +25C TA = -40C to +85C MIN TYP 1.7 1.4 MHz 1.2 0.6 20 50 100 0.5 2.5 4.0 % V/V MAX UNITS
Bandwidth
BW
VOS
OUT Settling Time to 1% of Final Value OUT Output Resistance
Note 1: All devices are 100% production tested at TA = +25C. All temperature limits are guaranteed by design. Note 2: Guaranteed by Total Output Voltage Error Test. Note 3: Total OUT Voltage Error is the sum of gain and offset voltage errors. Note 4: +6.25mV = 1/16 of +100mV full-scale voltage. Note 5: VSENSE such that output stage is in saturation. Note 6: VOS is extrapolated from the Gain Accuracy tests. Note 7: The device does not experience phase reversal when overdriven.
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier MAX4173T/F/H
Typical Operating Characteristics
(VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4173 TOC01
SUPPLY CURRENT vs. TEMPERATURE
500 SUPPLY CURRENT (A) 450 400 350 300 250 200 150 MAX4173H MAX4173F
MAX4173 toc02
SUPPLY CURRENT vs. RS+ VOLTAGE
MAX4173 toc03
440 430 SUPPLY CURRENT (A) 420 410 400 390 380 370 0 5 10 15 20 25 MAX4173H MAX4173F MAX4173T
550 MAX4173T
1.4 1.2 SUPPLY CURRENT (mA) 1.0 0.8 0.6 MAX4173F 0.4 0.2 0 MAX4173H MAX4173T
30
-50 -35 -20
-5
10
25
40
55
70
85
0
0.5
1.0
1.5 VRS+ (V)
2.0
2.5
28
SUPPLY VOLTAGE (V)
TEMPERATURE (C)
TOTAL OUTPUT ERROR vs. SUPPLY VOLTAGE
MAX4173 toc04
TOTAL OUTPUT ERROR vs. SUPPLY VOLTAGE
MAX4173 toc05
TOTAL OUTPUT ERROR vs. FULL-SCALE SENSE VOLTAGE
VCC = 28V 3 TOTAL OUTPUT ERROR (%) 2 1 0 MAX4173T -1 MAX4173F MAX4173H
MAX4173 toc06 MAX4173 toc09
0.60 0.45 TOTAL OUTPUT ERROR (%) 0.30 0.15 0 MAX4173H -0.15 -0.30 -0.45 VSENSE = 100mV -0.60 0 5 10 15 20 25 MAX4173F MAX4173T
6 4 TOTAL OUTPUT ERROR (%) MAX4173H 2 0 MAX4173F -2 -4 VSENSE = 6.25mV -6 MAX4173T
4
-2 0 5 10 15 20 25 30 0 50 100 VSENSE (mV) 150 200 SUPPLY VOLTAGE (V)
30
SUPPLY VOLTAGE (V)
POWER-SUPPLY REJECTION vs. FREQUENCY
-10 -20 -30 PSR (dB) -40 -50 -60 -70 -80 -90 -100 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
MAX4173 toc07
TOTAL OUTPUT ERROR vs. COMMON-MODE VOLTAGE
4 TOTAL OUTPUT ERROR (%) 2 0 -2 -4 -6 -8 -10 0 5 10 15 20 25 30 COMMON-MODE VOLTAGE (V) -0.8 -1.2 MAX4173F MAX4173H MAX4173T
MAX4173 toc08
GAIN ACCURACY vs. TEMPERATURE
1.2 0.8 GAIN ACCURACY (%) MAX4173T 0.4 0 -0.4 MAX4173H
0
6
MAX4173F
-50 -35 -20
-5
10
25
40
55
70
85
TEMPERATURE (C)
4
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier
Typical Operating Characteristics (continued)
(VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA = +25C, unless otherwise noted.)
TOTAL OUTPUT ERROR vs. TEMPERATURE
MAX4173 toc10
MAX4173T/F/H
MAX4173T LARGE-SIGNAL TRANSIENT RESPONSE (VSENSE = 6mV to 100mV)
CL = 5pF
MAX4173 toc11
2.0 1.5 TOTAL OUTPUT ERROR (%) 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 -50 -35 -20 -5 10 25 40 55 70 MAX4173F MAX4173T MAX4173H
100mV
IN (45mV/div)
6mV 2V
OUT (500mV/div) 0.120V
85
2s/div
TEMPERATURE (C)
MAX4173F LARGE-SIGNAL TRANSIENT RESPONSE (VSENSE = 6mV to 100mV)
MAX4173 toc12
MAX4173H LARGE-SIGNAL TRANSIENT RESPONSE (VSENSE = 6mV to 100mV)
CL = 5pF 100mV IN (45mV/div)
MAX4173 toc13
CL = 5pF
100mV
IN (45mV/div)
6mV
6mV 10V
5V OUT (2V/div) 0.3V
OUT (3V/div) 0.6V
2s/div
2s/div
MAX4173T SMALL-SIGNAL TRANSIENT RESPONSE (VSENSE = 95mV TO 100mV)
MAX4173 toc14
MAX4173F SMALL-SIGNAL TRANSIENT RESPONSE (VSENSE = 95mV TO 100mV)
CL = 5pF 100mV 95mV IN (5mV/div)
MAX4173 toc16
CL = 5pF IN (5mV/div)
100mV 95mV
2.0V OUT (50mV/div) 1.9V 5V OUT (100mV/div) 4.75V 2s/div 2s/div
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier MAX4173T/F/H
Typical Operating Characteristics (continued)
(VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA = +25C, unless otherwise noted.)
MAX4173H SMALL-SIGNAL TRANSIENT RESPONSE (VSENSE = 95mV to 100mV)
CL = 5pF IN (5mV/div)
MAX4173 toc15
START-UP DELAY (VCC = 0 to 4V) (VSENSE = 100mV)
MAX4173 toc17
100mV 95mV IN (2V/div)
4V
0V
2V 10V OUT (200mV/div) 9.5V 2s/div 5s/div OUT (1V/div) 0V
Pin Description
PIN NAME SOT23 1, 2 3 4 5 6 - SO 3 1 8 6 4 2, 5, 7 GND VCC RS+ RSOUT N.C. Ground Supply Voltage Input. Bypass to GND with a 0.1F capacitor. Power-Side Connection to the External Sense Resistor Load-Side Connection for the External Sense Resistor Voltage Output. VOUT is proportional to VSENSE ( VRS+ - VRS- ). Output impedance is approximately 12k. No Connection. Not internally connected. FUNCTION
6
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier
Detailed Description
The MAX4173 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 out of a battery in deep discharge and also enables high-side current sensing at voltages greater than the supply voltage (VCC). The MAX4173 operates as follows: Current from the source flows through RSENSE to the load (Figure 1). Since the internal-sense amplifier's inverting input has high impedance, negligible current flows through RG2 (neglecting the input bias current). Therefore, the sense amplifier's inverting-input voltage equals VSOURCE - (ILOAD)(RSENSE). The amplifier's open-loop gain forces its noninverting input to the same voltage as the inverting input. Therefore, the drop across RG1 equals (ILOAD)(RSENSE). Since IRG1 flows through RG1, IRG1 = (ILOAD)(RSENSE) / RG1. The internal current mirror multiplies I RG1 by a current gain factor, , to give IRGD = * IRG1. Solving IRGD = * (ILOAD)(RSENSE) / RG1. Assuming infinite output impedance, VOUT = (IRGD) (RGD). Substituting in for IRGD and rearranging, VOUT = * (RGD / RG1)(RSENSE * ILOAD). The parts gain equals * RGD / RG1. Therefore, VOUT = (GAIN) (RSENSE) (ILOAD), where GAIN = 20 for MAX4173T, GAIN = 50 for MAX4173F, and GAIN = 100 for MAX4173H.
ILOAD TO LOAD BATTERY RSRG2
Set the full-scale output range by selecting RSENSE and the appropriate gain version of the MAX4173.
MAX4173T/F/H
Applications Information
Recommended Component Values
The MAX4173 senses a wide variety of currents with different sense resistor values. Table 1 lists common resistor values for typical operation of the MAX4173.
Choosing RSENSE To measure lower currents more accurately, use a high value for RSENSE. The high value develops a higher sense voltage that reduces offset voltage errors of the internal op amp. In applications monitoring very high currents, RSENSE must be able to dissipate the 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. If ISENSE has a large high-frequency component, minimize the inductance of RSENSE. Wire-wound resistors have the highest inductance, metal-film resistors are somewhat better, and low-inductance metal-film resistors are best suited for these applications. Using a PCB 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 approximately 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, do not exceed the maximum power dissipation of the copper trace.
For example, the MAX4173T (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 0.1 inchwide copper trace.
VSOURCE 0 TO +28V RS+ IRG1 +3V TO +28V VCC RG1
RSENSE
A1
MAX4173
CURRENT MIRROR IRGD RGD = 12k GND OUT VOUT
Output Impedance
The output of the MAX4173 is a current source driving a 12k resistance. Resistive loading added to OUT reduces the output gain of the MAX4173. To minimize output errors for most applications, connect OUT to a high-impedance input stage. When output buffering is required, choose an op amp with a common-mode input range and an output voltage swing that includes ground when operating with a single supply. The op
Figure 1. Functional Diagram
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier MAX4173T/F/H
Table 1. Recommended Component Values
FULL-SCALE LOAD CURRENT ILOAD (A) CURRENT-SENSE RESISTOR RSENSE (m) GAIN 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
INPUT 0.3 in. COPPER
RSENSE 0.1 in. COPPER
LOAD/BATTERY
+
VSENSE RS+ RSVCC
_
0.3 in. COPPER
VIN
LOW-COST 0 TO +28V SWITCHING REGULATOR +3V TO +28V RS+ VCC
VSENSE RSENSE RS-
ILOAD
+3V TO +28V 0.1F 0.1F
MAX4173 MAX4173T OUT OUT GND GND LOAD/ BATTERY
Figure 2. MAX4173 Connections Showing Use of PC Board
Figure 3. Current Source
amp's supply voltage range should be at least as high as any voltage the system may encounter. The percent error introduced by output loading is determined with the following formula: RLOAD %ERROR = 100 - 1 12k + RLOAD where RLOAD is the external load applied to OUT.
Current Source Circuit
Figure 3 shows a block diagram using the MAX4173 with a switching regulator to make a current source.
8
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier
Pin Configurations
TOP VIEW
+ GND 1 6 OUT VCC 1 N.C. 5 RSGND VCC 3 4 RS+ 3 2 + 8 RS+ N.C. RSN.C.
MAX4173T/F/H
GND 2
MAX4173
MAX4173
7 6 5
OUT 4
SOT23
SO
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.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 8 SO 6 SOT23 PACKAGE CODE S8+4 U6+2 OUTLINE NO. 21-0041 21-0058 LAND PATTERN NO. 90-0096 90-0175
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Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier MAX4173T/F/H
Revision History
REVISION NUMBER 4 5 REVISION DATE 6/10 4/11 DESCRIPTION Clarified 0V to 2V is not a high-accuracy range for the device, added lead-free options and soldering temperature Updated VRS+ conditions to synchronize with tested material PAGES CHANGED 1, 2 2, 3
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) 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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