AVAILABLE
Functional Diagrams
Pin Configurations appear at end of data sheet.
Functional Diagrams continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
General Description
The MAX4173 low-cost, precision, high-side current-
sense 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 cur-
rent 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 con-
nected 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 user-
selectable external sense resistor sets the full-scale
current reading. This feature offers a high level of inte-
gration, resulting in a simple and compact current-
sense solution.
The MAX4173 operates from a single +3V to +28V sup-
ply, typically draws only 420µA of supply current over
the extended operating temperature range (-40°C to
+85°C), and is offered in the space-saving SOT23
package.
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
Features
oLow-Cost, Compact Current-Sense Solution
oHigh Accuracy +2V to +28V Common-Mode
Range, Functional Down to 0V, Independent of
Supply Voltage
oThree Gain Versions Available
+20V/V (MAX4173T)
+50V/V (MAX4173F)
+100V/V (MAX4173H)
o±0.5% Full-Scale Accuracy
o±3mV Input Offset Voltage (MAX4173T)
oWide 1.7MHz Bandwidth (MAX4173T)
o420µA Supply Current
oAvailable in Space-Saving SOT23 Package
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
MAX4173T/F/H
RSENSE
0 TO +28V ILOAD
VSENSE
VCC
OUT
GND
RS+
+3V TO +28V RS-
LOAD/
BATTERY
A/D
CONVERTER
0.1µF
Typical Operating Circuit
PART
MAX4173TEUT+T
MAX4173TESA+
PIN-PACKAGE
6 SOT23
8 SO
Ordering Information
-40°C to +85°C
-40°C to +85°C
TEMP RANGE SOT TOP MARK
AABN
—
MAX4173FEUT+T -40°C to +85°C 6 SOT23 AABO
MAX4173FESA+ -40°C to +85°C 8 SO —
MAX4173HEUT+T -40°C to +85°C 6 SOT23 AABP
MAX4173HESA+ -40°C to +85°C 8 SO —
20
20
GAIN (V/V)
50
50
100
100
Pin Configurations appear at end of data sheet.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
T
= Tape and reel.
MAX4173
19-1434; Rev 5; 4/11
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
ABSOLUTE MAXIMUM RATINGS
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 = +25°C.) (Note 1)
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.
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= +70°C)
8-Pin SO (derate 5.88mW/°C above +70°C)............... 471mW
SOT23-6 (derate 8.7mW/°C above +70°C)................. 696mW
Operating Temperature Range .......................... -40°C to +85°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................ +300°C
Soldering Temperature (reflow) ...................................... +260°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Operating Voltage Range VCC Guaranteed by PSR test 3 28 V
Common-Mode Input Range VCMR (Note 2) 0 28 V
Common-Mode Rejection CMR VRS+ > +2.0V 90 dB
Supply Current ICC VRS+ > +2.0V, VCC > 12V 0.42 1.0 mA
Leakage Current IRS+, IRS- VCC = 0V, VRS+ = 28V 0.3 3 µA
VRS+ > +2.0V 0 50
IRS+ VRS+ ≤ +2.0V -350 50
VRS+ > +2.0V 0 100
Input Bias Current
IRS- VRS+ ≤ +2.0V -700 100
µA
Full-Scale Sense Voltage VSENSE VSENSE = VRS+ - VRS- 150 mV
VSENSE = +100mV, VCC = +12V, VRS+ = +12V ±0.5 5.75
VSENSE = +100mV, VCC = +12V, VRS+ = +12V,
TA = +25°C 0.5 3.25
VSENSE = +100mV, VCC = +28V, VRS+ = +28V 0.5 5.75
VSENSE = +100mV, VCC = +12V, VRS+ = +0.1V -9 ±24
Total OUT Voltage Error
(Note 3)
VCC = +12V, VRS+ = +12V, VSENSE = +6.25mV
(Note 4) ±7.5
%
MAX4173T, VCC = +3.0V, VRS+ = 28V,
VSENSE = 250mV 0.8 1.2
MAX4173F, VCC = +7.5V, VRS+ = 28V,
VSENSE = 250mV 0.8 1.2
Out High Voltage (Note 5) (VCC - VOH)
MAX4173H, VCC = +15V, VRS+ = 28V,
VSENSE = 250mV 0.8 1.2
V
TA = +25°C 1.2 5
OUT Low Voltage VOL
MAX4173TEUT,
VCC = +5V, VRS+ = 0.89V,
VSENSE = 0mV TA = -40°C to +85°C 40
mV
2
Maxim Integrated
MAX4173
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
Note 1: All devices are 100% production tested at TA = +25°C. 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.
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 = +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX4173T,
VSENSE = +100mV 1.7
MAX4173F,
VSENSE = +100mV 1.4
MAX4173H,
VSENSE = +100mV 1.2
Bandwidth BW
VRS+ = +12V,
VCC = +12V,
CLOAD = 5pF
VSENSE = +6.25mV
(Note 4) 0.6
MHz
MAX4173T 20
MAX4173F 50Gain AV
MAX4173H 100
V/V
TA = +25°C 0.5 ±2.5
∆AV
MAX4173T/F VSENSE =
+10mV to +150mV,
VCC = VRS+ = 12V TA = -40°C to +85°C 4.0
TA = +25°C 0.5 ±2.5
Gain Accuracy
∆AV
MAX4173H VSENSE =
+10mV to +100mV,
VCC = VRS+ = 12V TA = -40°C to +85°C 4.0
%
TA = +25°C 0.3 ±3
Input Offset Voltage
(Note 6) VOS MAX4173TEUT,
VRS+ = 12V TA = -40°C to +85°C ±5 mV
VSENSE = +6.25mV
to +100mV 400
OUT Settling Time to 1% of
Final Value
VCC = +12V, VRS+ = 12V,
CLOAD = 5pF VSENSE = +100mV
to +6.25mV 800
ns
OUT Output Resistance ROUT 12 kΩ
MAX4173T, VSENSE = 80mV, VRS+ ≥ +2V 60 84
MAX4173F, VSENSE = 32mV, VRS+ ≥ +2V 60 91
Power-Supply Rejection PSR
MAX4173H, VSENSE = 16mV, VRS+ ≥ +2V 60 95
dB
Power-Up Time to 1% of
Final Value VSENSE = +100mV, CLOAD = 5pF 10 µs
Saturation Recovery Time VCC = +12V, VRS+ = 12V (Note 7) 10 µs
Maxim Integrated
MAX4173
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
370
390
380
410
400
430
420
440
010155 202530
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4173 TOC01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
MAX4173T
MAX4173F
MAX4173H
200
300
250
450
400
350
550
500
150
-50 -5 10-35-20 2540557085
SUPPLY CURRENT vs. TEMPERATURE
MAX4173 toc02
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
MAX4173T
MAX4173F
MAX4173H
0
0.4
0.2
0.8
0.6
1.2
1.0
1.4
0 1.0 1.50.5 2.0 2.5 28
SUPPLY CURRENT vs. RS+ VOLTAGE
MAX4173 toc03
VRS+ (V)
SUPPLY CURRENT (mA)
MAX4173T
MAX4173H
MAX4173F
-0.60
-0.45
-0.30
-0.15
0
0.15
0.30
0.45
0.60
0105 15202530
TOTAL OUTPUT ERROR vs.
SUPPLY VOLTAGE
MAX4173 toc04
SUPPLY VOLTAGE (V)
TOTAL OUTPUT ERROR (%)
MAX4173F
VSENSE = 100mV
MAX4173T
MAX4173H
0
-100
100 1k 10k 100k 1M 10M
POWER-SUPPLY REJECTION
vs. FREQUENCY
-80
MAX4173 toc07
FREQUENCY (Hz)
PSR (dB)
-60
-40
-20
-10
-90
-70
-50
-30
-6
-2
-4
2
0
4
6
010155 202530
TOTAL OUTPUT ERROR
vs. SUPPLY VOLTAGE
MAX4173 toc05
SUPPLY VOLTAGE (V)
TOTAL OUTPUT ERROR (%)
MAX4173F
VSENSE = 6.25mV
MAX4173H
MAX4173T
-2
0
-1
2
1
3
4
0 10050 150 200
TOTAL OUTPUT ERROR vs.
FULL-SCALE SENSE VOLTAGE
MAX4173 toc06
VSENSE (mV)
TOTAL OUTPUT ERROR (%)
MAX4173F
VCC = 28V
MAX4173H
MAX4173T
-10
-8
-6
-4
-2
0
2
4
6
0105 15202530
TOTAL OUTPUT ERROR vs.
COMMON-MODE VOLTAGE
MAX4173 toc08
COMMON-MODE VOLTAGE (V)
TOTAL OUTPUT ERROR (%)
MAX4173F
MAX4173TMAX4173H
Typical Operating Characteristics
(VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA= +25°C, unless otherwise noted.)
-1.2
-0.4
-0.8
0
0.4
0.8
1.2
-50 -20 -5 10-35 2540557085
GAIN ACCURACY vs. TEMPERATURE
MAX4173 toc09
TEMPERATURE (°C)
GAIN ACCURACY (%)
MAX4173F
MAX4173H
MAX4173T
4
Maxim Integrated
MAX4173
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
Typical Operating Characteristics (continued)
(VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA= +25°C, unless otherwise noted.)
-2.0
-1.0
-1.5
0.5
0
-0.5
1.5
1.0
2.0
-50 -5 10-35 -20 25 40 55 70 85
TOTAL OUTPUT ERROR
vs. TEMPERATURE
MAX4173 toc10
TEMPERATURE (°C)
TOTAL OUTPUT ERROR (%)
MAX4173H
MAX4173T
MAX4173F
2µs/div
MAX4173T
LARGE-SIGNAL TRANSIENT RESPONSE
(VSENSE = 6mV to 100mV)
IN
(45mV/div)
OUT
(500mV/div)
6mV
100mV
2V
0.120V
MAX4173 toc11
CL = 5pF
2µs/div
MAX4173F
LARGE-SIGNAL TRANSIENT RESPONSE
(VSENSE = 6mV to 100mV)
IN
(45mV/div)
OUT
(2V/div)
6mV
100mV
5V
0.3V
MAX4173 toc12
CL = 5pF
2µs/div
MAX4173H
LARGE-SIGNAL TRANSIENT RESPONSE
(VSENSE = 6mV to 100mV)
IN
(45mV/div)
OUT
(3V/div)
6mV
100mV
10V
0.6V
MAX4173 toc13
CL = 5pF
2µs/div
MAX4173T
SMALL-SIGNAL TRANSIENT RESPONSE
(VSENSE = 95mV TO 100mV)
IN
(5mV/div)
OUT
(50mV/div)
95mV
100mV
2.0V
1.9V
MAX4173 toc14
CL = 5pF
2µs/div
MAX4173F
SMALL-SIGNAL TRANSIENT RESPONSE
(VSENSE = 95mV TO 100mV)
IN
(5mV/div)
OUT
(100mV/div)
95mV
100mV
5V
4.75V
MAX4173 toc16
CL = 5pF
Maxim Integrated
MAX4173
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
Pin Description
Typical Operating Characteristics (continued)
(VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA= +25°C, unless otherwise noted.)
2µs/div
MAX4173H
SMALL-SIGNAL TRANSIENT RESPONSE
(VSENSE = 95mV to 100mV)
IN
(5mV/div)
OUT
(200mV/div)
95mV
100mV
10V
9.5V
MAX4173 toc15
CL = 5pF
5µs/div
START-UP DELAY (VCC = 0 to 4V)
(VSENSE = 100mV)
IN
(2V/div)
OUT
(1V/div)
0V
4V
2V
0V
MAX4173 toc17
6Load-Side Connection for the External Sense ResistorRS-5
FUNCTIONNAME
SO
PIN
SOT23
1Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.VCC
3
4Voltage Output. VOUT is proportional to VSENSE ( VRS+ - VRS- ). Output impedance is
approximately 12kΩ.
OUT6
3GroundGND1, 2
8Power-Side Connection to the External Sense ResistorRS+4
2, 5, 7 No Connection. Not internally connected.N.C.–
6
Maxim Integrated
MAX4173
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
Detailed Description
The MAX4173 high-side current-sense amplifier fea-
tures 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 IRG1 by a current gain factor, β, to give
IRGD = β·IRG1. Solving IRGD = β·(ILOAD)(RSENSE) /
RG1. Assuming infinite output impedance, VOUT = (IRGD)
(RGD). Substituting in for IRGD and rearranging, VOUT =
β·(RGD / RG1)(RSENSE ·ILOAD). The parts gain equals
β·RGD / RG1. Therefore, VOUT = (GAIN) (RSENSE)
(ILOAD), where GAIN = 20 for MAX4173T, GAIN = 50 for
MAX4173F, and GAIN = 100 for MAX4173H.
Set the full-scale output range by selecting RSENSE and
the appropriate gain version of the MAX4173.
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 maxi-
mum ratings.
If ISENSE has a large high-frequency component, mini-
mize the inductance of RSENSE. Wire-wound resistors
have the highest inductance, metal-film resistors are
somewhat better, and low-inductance metal-film resis-
tors 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 30mΩ/ft. The resis-
tance-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 cur-
rent of 10A and an RSENSE of 5mΩ) 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 inch-
wide copper trace.
Output Impedance
The output of the MAX4173 is a current source driving a
12kΩresistance. 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
RSENSE
VSOURCE
0 TO +28V
+3V TO +28V
RGD = 12k
VOUT
IRG1
IRGD
ILOAD
RG1 RG2
RS-RS+
OUT
GND
TO LOAD BATTERY
VCC
CURRENT
MIRROR
A1
MAX4173
Figure 1. Functional Diagram
Maxim Integrated
MAX4173
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
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:
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.
% 100 R
12k R
1
ERROR LOAD
LOAD
=Ω+ −
⎛
⎝
⎜⎞
⎠
⎟
Table 1. Recommended Component Values
MAX4173T
VSENSE
RSENSE
+3V TO +28V
0.1µF
RS+
+
0.3 in. COPPER
INPUT LOAD/BATTERY
0.3 in. COPPER0.1 in. COPPER
RS-
GND
OUT
VCC
_
Figure 2. MAX4173 Connections Showing Use of PC Board Figure 3. Current Source
MAX4173
RSENSE
ILOAD
0 TO +28V VSENSE
VCC
OUT
VIN
GND
RS+
+3V TO +28V
0.1µF
RS-
LOAD/
BATTERY
LOW-COST
SWITCHING
REGULATOR
10.0100
5.050
2.0
10 10
20
10.0100
5.050
2.0
520
20
10.0100
5.050
2.0
1100
20
10.0100
5.0501000
CURRENT-SENSE RESISTOR
RSENSE (mΩΩ)
20
GAIN
2.0
0.1
FULL-SCALE OUTPUT VOLTAGE
(FULL-SCALE VSENSE = 100mV)
VOUT (V)
FULL-SCALE LOAD CURRENT
ILOAD (A)
8
Maxim Integrated
MAX4173
RS-
N.C.OUT
1
2
8
7
RS+
N.C.N.C.
GND
VCC
3
4
6
5
MAX4173
SO
+
Pin Configurations
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
5 RS-
GND
GND
RS+VCC
1
+
6 OUT
MAX4173
2
34
SOT23
TOP VIEW
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 SO S8+4 21-0041 90-0096
6 SOT23 U6+2 21-0058 90-0175
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.
Maxim Integrated
MAX4173
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
4 6/10 Clarified 0V to 2V is not a high-accuracy range for the device, added lead-free
options and soldering temperature 1, 2
5 4/11 Updated VRS+ conditions to synchronize with tested material 2, 3
MAX4173
10 Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
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. 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.
© 2011 Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.