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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 420A of supply current over
the extended operating temperature range (-40C to
+85C), and is offered in the space-saving SOT23-6
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
o
Low-Cost, Compact Current-Sense Solution
o
Wide 0 to +28V Common-Mode Range
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
420A Supply Current
o
Wide 1.7MHz Bandwidth (MAX4173T)
o
+3V to +28V Operating Supply
o
Available in Space-Saving SOT23-6 Package
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
________________________________________________________________
Maxim Integrated Products
1
MAX4173T/F/H
R
SENSE
0 TO +28V
I
LOAD
V
SENSE
V
CC
OUT
GND
RS+
+3V TO +28V
RS-
LOAD/
BATTERY
A/D
CONVERTER
0.1
F
Typical Operating Circuit
19-1434; Rev 1; 5/99
PART
MAX4173TEUT-T
MAX4173TESA
PIN-PACKAGE
6 SOT23-6
8 SO
Ordering Information
-40C to +85C
-40C to +85C
TEMP. RANGE
SOT TOP MARK
AABN
MAX4173FEUT-T
-40C to +85C
6 SOT23-6
AABD
MAX4173FESA
-40C to +85C
8 SO
MAX4173HEUT-T
-40C to +85C
6 SOT23-6
AABP
MAX4173HESA
-40C to +85C
8 SO
20
20
GAIN (V/V)
50
50
100
100
Pin Configurations appear at end of data sheet.
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
RS+
= 0 to +28V, V
CC
= +3V to +28V, V
SENSE
= 0, T
A
= T
MIN
to T
MAX
, R
LOAD
=
unless otherwise noted. Typical values are at
T
A
= +25C.) (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.
V
CC
, RS+, RS- to GND .......................................... -0.3V to +30V
OUT to GND .............................................. -0.3V to (V
CC
+ 0.3V)
Output Short-Circuit to V
CC
or GND ......................... Continuous
Differential Input Voltage (V
RS+
- V
RS-
) ............................. 0.3V
Current into Any Pin......................................................... 20mA
Continuous Power Dissipation (T
A
= +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, 10sec) ............................ +300C
V
RS+
> +2.0V
(Note 2)
Guaranteed by PSR test
V
SENSE
= +100mV, V
CC
= +12V, V
RS+
= +12V
V
SENSE
= V
RS+
- V
RS-
V
CC
= +12V, V
RS+
=+12V, V
SENSE
= +6.25mV
(Note 4)
V
SENSE
= +100mV, V
CC
= +12V, V
RS+
= +0.1V
V
RS+
+2.0V
V
RS+
> +2.0V
V
RS+
> +2.0V, V
CC
= 12V
V
CC
= 0
V
RS+
> +2.0V
V
SENSE
= +100mV, V
CC
= +28V, V
RS+
= +28V
V
RS+
+2.0V
V
SENSE
= +100mV, V
CC
= +12V, V
RS+
= +12V,
T
A
= +25C
CONDITIONS
V
7.5
-9
24
0.5
5.75
0.5
3.25
dB
90
CMR
Common-Mode Rejection
V
0
28
V
CMR
V
3
28
V
CC
Operating Voltage Range
Common-Mode Input Range
%
0.5
5.75
mV
150
V
SENSE
Full-Scale Sense Voltage
-700
100
0
100
I
RS-
mA
0.42
1.0
I
CC
Supply Current
A
0.3
3
I
RS+
, I
RS-
Leakage Current
0
50
I
RS+
Input Bias Current
-350
50
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
Total OUT Voltage Error
(Note 3)
A
MAX4173T, V
CC
= +3.0V
(V
CC
-
V
OH
)
OUT High Voltage
(Note 5)
0.8
1.2
MAX4173H, V
CC
= +15V
0.8
1.2
MAX4173F, V
CC
= +7.5V
0.8
1.2
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
_______________________________________________________________________________________
3
Note 1:
All devices are 100% production tested at T
A
= +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:
V
SENSE
such that output stage is in saturation.
Note 6:
The device does not experience phase reversal when overdriven.
ELECTRICAL CHARACTERISTICS (continued)
(V
RS+
= 0 to +28V, V
CC
= +3V to +28V, V
SENSE
= 0, T
A
= T
MIN
to T
MAX
, R
LOAD
=
unless otherwise noted. Typical values are at
T
A
= +25C.) (Note 1)
MAX4173T, V
SENSE
= 80mV, V
RS+
+2V
MAX4173T
V
SENSE
= +100mV to +6.25mV
MAX4173F,
V
SENSE
= +100mV,
MAX4173T,
V
SENSE
= +100mV,
T
A
= +25C
MAX4173F
MAX4173H
T
A
= +25C
dB
60
84
PSR
Power-Supply Rejection
k
12
R
OUT
OUT Output Resistance
ns
800
OUT Settling Time to 1% of
Final Value
V/V
20
A
V
Gain
1.4
MHz
1.7
BW
Bandwidth
0.5
2.5
50
100
%
0.5
2.5
A
V
Gain Accuracy
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
V
CC
= +12V,
V
RS+
= +12V,
C
LOAD
= 5pF
V
RS+
= +12V,
V
CC
= +12V,
C
LOAD
= 5pF
MAX4173H
V
SENSE
= +10mV
to +100mV
MAX4173T/F
V
SENSE
= +10mV
to +150mV
CONDITIONS
MAX4173H,
V
SENSE
= +100mV,
1.2
V
SENSE
= +6.25mV,
(Note 4)
0.6
MAX4173F, V
SENSE
= 32mV, V
RS+
+2V
60
91
MAX4173H, V
SENSE
= 16mV, V
RS+
+2V
60
95
V
SENSE
= +100mV, C
LOAD
= 5pF
s
10
Power-Up Time to 1% of Final
Value
V
CC
= +12V, V
RS+
= +12V (Note 6)
s
10
Saturation Recovery Time
4.0
T
A
= -40C to +85C
4.0
T
A
= -40C to +85C
400
V
SENSE
= +6.25mV to +100mV
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
4
_______________________________________________________________________________________
370
390
380
410
400
430
420
440
0
10
15
5
20
25
30
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4173 TOC01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
A)
MAX4173T
MAX4173F
MAX4173H
200
300
250
450
400
350
550
500
150
-50
-5
10
-35 -20
25
40
55
70
85
SUPPLY CURRENT vs. TEMPERATURE
MAX4173 toc02
TEMPERATURE (C)
SUPPLY CURRENT (
A)
MAX4173T
MAX4173F
MAX4173H
0
0.4
0.2
0.8
0.6
1.2
1.0
1.4
0
1.0
1.5
0.5
2.0
2.5
28
SUPPLY CURRENT vs. RS+ VOLTAGE
MAX4173 toc03
V
RS+
(V)
SUPPLY CURRENT (mA)
MAX4173T
MAX4173H
MAX4173F
-0.60
-0.45
-0.30
-0.15
0
0.15
0.30
0.45
0.60
0
10
5
15
20
25
30
TOTAL OUTPUT ERROR vs.
SUPPLY VOLTAGE
MAX4173 toc04
SUPPLY VOLTAGE (V)
TOTAL OUTPUT ERROR (%)
MAX4173F
V
SENSE
= 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
0
10
15
5
20
25
30
TOTAL OUTPUT ERROR
vs. SUPPLY VOLTAGE
MAX4173 toc05
SUPPLY VOLTAGE (V)
TOTAL OUTPUT ERROR (%)
MAX4173F
V
SENSE
= 6.25mV
MAX4173H
MAX4173T
-2
0
-1
2
1
3
4
0
100
50
150
200
TOTAL OUTPUT ERROR vs.
FULL-SCALE SENSE VOLTAGE
MAX4173 toc06
V
SENSE
(mV)
TOTAL OUTPUT ERROR (%)
MAX4173F
V
CC
= 28V
MAX4173H
MAX4173T
-10
-8
-6
-4
-2
0
2
4
6
0
10
5
15
20
25
30
TOTAL OUTPUT ERROR vs.
COMMON-MODE VOLTAGE
MAX4173 toc08
COMMON-MODE VOLTAGE (V)
TOTAL OUTPUT ERROR (%)
MAX4173F
MAX4173T
MAX4173H
Typical Operating Characteristics
(V
CC
= +12V, V
RS+
= +12V, V
SENSE
= +100mV, T
A
= +25C, unless otherwise noted.)
-1.2
-0.4
-0.8
0
0.4
0.8
1.2
-50
-20
-5
10
-35
25
40
55
70
85
GAIN ACCURACY vs. TEMPERATURE
MAX4173 toc09
TEMPERATURE (C)
GAIN ACCURACY (%)
MAX4173F
MAX4173H
MAX4173T
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
_______________________________________________________________________________________
5
Typical Operating Characteristics (continued)
(V
CC
= +12V, V
RS+
= +12V, V
SENSE
= +100mV, T
A
= +25C, 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
2
s/div
MAX4173T
LARGE-SIGNAL TRANSIENT RESPONSE
(V
SENSE
= 6mV to 100mV)
IN
(45mV/div)
OUT
(500mV/div)
6mV
100mV
2V
0.120V
MAX4173 toc11
C
L
= 5pF
2
s/div
MAX4173F
LARGE-SIGNAL TRANSIENT RESPONSE
(V
SENSE
= 6mV to 100mV)
IN
(45mV/div)
OUT
(2V/div)
6mV
100mV
5V
0.3V
MAX4173 toc12
C
L
= 5pF
2
s/div
MAX4173H
LARGE-SIGNAL TRANSIENT RESPONSE
(V
SENSE
= 6mV to 100mV)
IN
(45mV/div)
OUT
(3V/div)
6mV
100mV
10V
0.6V
MAX4173 toc13
C
L
= 5pF
2
s/div
MAX4173T
SMALL-SIGNAL TRANSIENT RESPONSE
(V
SENSE
= 95mV TO 100mV)
IN
(5mV/div)
OUT
(50mV/div)
95mV
100mV
2.0V
1.9V
MAX4173 toc14
C
L
= 5pF
2
s/div
MAX4173F
SMALL-SIGNAL TRANSIENT RESPONSE
(V
SENSE
= 95mV TO 100mV)
IN
(5mV/div)
OUT
(100mV/div)
95mV
100mV
5V
4.75V
MAX4173 toc16
C
L
= 5pF
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
6
_______________________________________________________________________________________
Pin Description
Typical Operating Characteristics (continued)
(V
CC
= +12V, V
RS+
= +12V, V
SENSE
= +100mV, T
A
= +25C, unless otherwise noted.)
2
s/div
MAX4173H
SMALL-SIGNAL TRANSIENT RESPONSE
(V
SENSE
= 95mV to 100mV)
IN
(5mV/div)
OUT
(200mV/div)
95mV
100mV
10V
9.5V
MAX4173 toc15
C
L
= 5pF
5
s/div
START-UP DELAY (V
CC
= 0 to 4V)
(V
SENSE
= 100mV)
IN
(2V/div)
OUT
(1V/div)
0V
4V
2V
0V
MAX4173 toc17
6
Load-Side Connection for the External Sense Resistor
RS-
5
FUNCTION
NAME
SO
PIN
SOT23-6
1
Supply Voltage Input. Bypass to GND with a 0.1F capacitor.
V
CC
3
4
Voltage Output. V
OUT
is proportional to V
SENSE
( V
RS+
- V
RS-
). Output impedance is
approximately 12k
.
OUT
6
3
Ground
GND
1, 2
8
Power-Side Connection to the External Sense Resistor
RS+
4
2, 5, 7
No Connection. Not internally connected.
N.C.
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
_______________________________________________________________________________________
7
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 (V
CC
).
The MAX4173 operates as follows: Current from the
source flows through R
SENSE
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
V
SOURCE
- (I
LOAD
)(R
SENSE
). The amplifier's open-loop
gain forces its noninverting input to the same voltage as
the inverting input. Therefore, the drop across RG1
equals (I
LOAD
)(R
SENSE
). Since I
RG1
flows through RG1,
I
RG1
= (I
LOAD
)(R
SENSE
) / RG1. The internal current mirror
multiplies I
RG1
by a current gain factor,
, to give
I
RGD
=
I
RG1
. Solving I
RGD
=
(I
LOAD
)(R
SENSE
) /
RG1. Assuming infinite output impedance, V
OUT
= (I
RGD
)
(RGD). Substituting in for I
RGD
and rearranging, V
OUT
=
(RGD / RG1)(R
SENSE
I
LOAD
). The parts gain equals
RGD / RG1. Therefore, V
OUT
= (GAIN) (R
SENSE
)
(I
LOAD
), where GAIN = 20 for MAX4173T, GAIN = 50 for
MAX4173F, and GAIN = 100 for MAX4173H.
Set the full-scale output range by selecting R
SENSE
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 R
SENSE
To measure lower currents more accurately, use a high
value for R
SENSE
. The high value develops a higher
sense voltage that reduces offset voltage errors of the
internal op amp.
In applications monitoring very high currents, R
SENSE
must be able to dissipate the I
2
R 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 I
SENSE
has a large high-frequency component, mini-
mize the inductance of R
SENSE
. 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 R
SENSE
If the cost of R
SENSE
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 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 R
SENSE
of 5m
) creates a full-scale
V
SENSE
of 50mV that yields a maximum V
OUT
of 1V.
R
SENSE
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
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
R
SENSE
V
SOURCE
0 TO +28V
+3V TO +28V
RGD
= 12k
V
OUT
I
RG1
I
RGD
I
LOAD
R
G1
R
G2
RS-
RS+
OUT
GND
TO LOAD BATTERY
V
CC
CURRENT
MIRROR
A1
MAX4173
Figure 1. Functional Diagram
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
8
_______________________________________________________________________________________
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 R
LOAD
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
=
+
-
Table 1. Recommended Component Values
MAX4173T
V
SENSE
R
SENSE
+3V TO +28V
0.1
F
RS+
+
0.3 in. COPPER
INPUT
LOAD/BATTERY
0.3 in. COPPER
0.1 in. COPPER
RS-
GND
OUT
V
CC
_
Figure 2. MAX4173 Connections Showing Use of PC Board
Figure 3. Current Source
MAX4173
R
SENSE
I
LOAD
0 TO +28V
V
SENSE
V
CC
OUT
V
IN
GND
RS+
+3V TO +28V
0.1
F
RS-
LOAD/
BATTERY
LOW-COST
SWITCHING
REGULATOR
10.0
100
5.0
50
2.0
10
10
20
10.0
100
5.0
50
2.0
5
20
20
10.0
100
5.0
50
2.0
1
100
20
10.0
100
5.0
50
1000
CURRENT-SENSE RESISTOR
R
SENSE
(m
)
20
GAIN
2.0
0.1
FULL-SCALE OUTPUT VOLTAGE
(FULL-SCALE V
SENSE
= 100mV)
V
OUT
(V)
FULL-SCALE LOAD CURRENT
I
LOAD
(A)
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
_______________________________________________________________________________________
9
TOP VIEW
RS-
N.C.
OUT
1
2
8
7
RS+
N.C.
N.C.
GND
V
CC
3
4
6
5
MAX4173
SO
Pin Configurations
Chip Information
TRANSISTOR COUNT: 187
5
RS-
GND
GND
RS+
V
CC
1
6
OUT
MAX4173
2
3
4
SOT23-6
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
10
______________________________________________________________________________________
Package Information
6LSOT.EPS
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
______________________________________________________________________________________
11
Package Information (continued)
SOICN.EPS
MAX4173T/F/H
Low-Cost, SOT23, Voltage-Output,
High-Side Current-Sense Amplifier
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.
12
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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.
12
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
NOTES
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