The MAX4172 is a low-cost, precision, high-side current-
sense amplifier for portable PCs, telephones, and other
systems where battery/DC power-line monitoring is critical.
High-side power-line monitoring is especially useful in
battery-powered systems, since it does not interfere with
the battery charger’s ground path. Wide bandwidth and
ground-sensing capability make the device suitable for
closed-loop battery-charger and general-purpose current-
source applications. The 0 to 32V input common-mode
range is independent of the supply voltage, which ensures
that current-sense feedback remains viable, even when
connected to a battery in deep discharge.
To provide a high level of flexibility, the MAX4172 functions
with an external sense resistor to set the range of load
current to be monitored. It has a current output that can
be converted to a ground-referred voltage with a single
resistor, accommodating a wide range of battery voltages
and currents.
An open-collector power-good output (PG) indicates
when the supply voltage reaches an adequate level
to guarantee proper operation of the current-sense
amplifier. The MAX4172 operates with a 3.0V to 32V
supply voltage, and is available in a space-saving, 8-pin
μMAX
®
or SO package.
●
Ideal for High-Side Monitoring
• 3V to 32V Supply Operation
• ±0.5% Typical Full-Scale Accuracy Over Temperature
• High Accuracy +2V to +32V Common-Mode
Range, Functional Down to 0V, Independent of
Supply Voltage
• 800kHz Bandwidth [V
SENSE
= 100mV (1C)]
• 200kHz Bandwidth [V
SENSE
= 6.25mV (C/16)]
●
Minimizes Board Space Requirements
•
μMAX and SO Packages
Ordering Information
PART
MAX4172ESA+
MAX4172EUA+
MAX4172GUA+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +105°C
PIN-PACKAGE
8 SO
8 μMAX
8 µMAX
+Denotes
a lead(Pb)-free/RoHS-compliant package.
Typical Operating Circuit
UNREGULATED
DC SUPPLY
3V TO 32V
R
SENSE
50mΩ
V
SENSE
Applications
●
●
●
●
●
●
●
Portable PCs: Notebooks/Subnotebooks/Palmtops
Battery-Powered/Portable Equipment
Closed-Loop Battery Chargers/Current Sources
Smart-Battery Packs
Portable/Cellular Phones
Portable Test/Measurement Systems
Energy Management Systems
LOW-COST
SWITCHING
REGULATOR
0 TO 32V
ANALOG OR
LOGIC SUPPLY
RS-
PG
100kΩ
2A
RS+
V+
MAX4172
OUT
GND
FEEDBACK LOOP
V
OUT
= 500mV/A
POWER GOOD
LOAD/
BATTERY
Pin Configuration
TOP VIEW
RS+ 1
RS- 2
N.C. 3
N.C. 4
µMAX/SO
I
OUT
=
V
SENSE
/ 100Ω
+
MAX4172
8
7
6
5
V+
PG
OUT
GND
R
OUT
1kΩ
LOW-COST BATTERY CHARGER/CURRENT SOURCE
μMAX is a registered trademark of Maxim Integrated Products, Inc.
19-1184; Rev 4; 6/16
MAX4172
Low-Cost, Precision, High-Side
Current-Sense Amplifier
Absolute Maximum Ratings
V+, RS+, RS-,
PG
.................................................-0.3V to +36V
OUT .............................................................-0.3V to (V+ + 0.3V)
Differential Input Voltage, V
RS+
- V
RS-
..........................±700mV
Current into Any Pin .........................................................±50mA
Continuous Power Dissipation (T
A
= +70°C)
SO (derate 5.88mW/°C above +70°C) ........................471mW
μMAX (derate 4.10mW/°C above +70°C)
...................330mW
Operating Temperature Range
MAX4172E_A ................................................. -40°C to +85°C
MAX4172G_A ............................................... -40°C to +105°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................. +300°C
Soldering Temperature (reflow) .......................................+260°C
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
(V+ = +3V to +32V; V
RS+
, V
RS-
= 0 to 32V; T
A
= T
MIN
to T
MAX
; unless otherwise noted. Typical values are at V+ = +12V,
V
RS+
= 12V, T
A
= +25°C.)
PARAMETER
Operating Voltage Range
Input Voltage Range
Supply Current
Input Offset Voltage
Positive Input Bias Current
Negative Input Bias
Current
Maximum V
SENSE
Voltage
Low-Level Current Error
SYMBOL
V+
V
RS-
I
V+
I
OUT
= 0mA
V+ = 12V, V
RS+
= 12V
V
RS+
≤ 2.0V
V
RS+
> 2.0V, I
OUT
= 0mA
V
RS+
≤ 2.0V, I
OUT
= 0mA
V
RS+
> 2.0V
V
RS+
≤ 2.0V
CONDITIONS
MIN
3
0
MAX4172ESA
MAX4172EUA
0
-325
0
-650
150
MAX4172ESA
MAX4172EUA
MAX4172ESA,
T
A
= -40°C to 0°C
Output Current Error
V
SENSE
= 100mV, V+ = 12V,
V
RS+
= 12V
MAX4172EUA,
T
A
= -40°C to 0°C
MAX4172ESA,
T
A
= 0°C to +105°C
MAX4172EUA,
T
A
= 0°C to +105°C
OUT Power-Supply
Rejection Ratio
OUT Common-Mode
Rejection Ratio
ΔI
OUT
/ΔV+
3V ≤ V+ ≤ 32V, V
RS+
> 2.0V
0.2
0.03
175
±8.0
±15
±20
±50
µA
±10
±15
μA/V
μA/V
50
0
0.8
±0.1
±0.2
4
27
42.5
+42.5
85
85
µA
µA
mV
µA
TYP
MAX
32
32
1.6
±0.75
±1.6
mV
UNITS
V
V
mA
V
OS
I
RS+
I
RS-
V
SENSE
= 6.25mV, V+ = 12V,
V
RS+
= 12V (Note 1)
ΔI
OUT
/ΔV
RS+
2.0V < V
RS+
< 32V
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Maxim Integrated
│
2
MAX4172
Low-Cost, Precision, High-Side
Current-Sense Amplifier
Electrical Characteristics (continued)
(V+ = +3V to +32V; V
RS+
, V
RS-
= 0 to 32V; T
A
= T
MIN
to T
MAX
; unless otherwise noted. Typical values are at V+ = +12V,
V
RS+
= 12V, T
A
= +25°C.)
PARAMETER
Maximum Output Voltage
(OUT)
Bandwidth
Maximum Output Current
Transconductance
V+ Threshold for
PG
Output Low (Note 2)
PG
Output Low Voltage
Leakage Current into
PG
Power-Off Input Leakage
Current (RS+, RS-)
OUT Rise Time
OUT Fall Time
OUT Settling Time to 1%
OUT Output Resistance
V
OL
I
OUT
G
m
SYMBOL
I
OUT
≤ 1.5mA
V
SENSE
= 100mV
800
200
1.5
9.8
9.7
1.75
10
10
2.77
2.67
0.4
1
0.1
400
800
1.3
6
20
1
10.2
10.3
V
SENSE
= 6.25mV (Note 1)
T
A
= 0°C to +105°C
G
m
= I
OUT
/(V
RS+
- V
RS-
),
V
SENSE
= 100mV, V
RS+
> 2.0V T
A
= -40°C to 0°C
V+ rising
V+ falling
I
SINK
= 1.2mA, V+ = 2.9V, T
A
= +25°C
V+ = 2.5V, T
A
= +25°C
V+ = 0V, V
RS+
= V
RS-
= 32V
V
SENSE
= 0 to 100mV, 10% to 90%
V
SENSE
= 5mV to 100mV
V
SENSE
= 150mV
V
SENSE
= 100mV to 0mV, 90% to 10%
Rising
Falling
CONDITIONS
MIN
TYP
MAX
V+ - 1.2
UNITS
V
kHz
mA
mA/V
V
V
µA
µA
ns
ns
µs
MΩ
Note 1:
6.25mV = 1/16 of typical full-scale sense voltage (C/16).
Note 2:
Valid operation of the MAX4172 is guaranteed by design when
PG
is low.
Typical Operating Characteristics
(V+ = +12V, V
RS+
= 12V, R
OUT
= 1kΩ, T
A
= +25°C, unless otherwise noted.)
MAX4172-01
MAX4172-02
QUIESCENT SUPPLY CURRENT (μA)
T
A
= +105°C
950
850
750
650
550
450
T
A
= -40°C
I
OUT
= 0mA
0
10
20
V+ (V)
30
T
A
= +85°C
0.9
0.8
0.7
ERROR (%)
0.6
0.5
0.4
0.3
0.2
0.1
T
A
= -40°C
V
SENSE
= 100mV
6
4
ERROR (%)
T
A
= +25°C
V
SENSE
= 6.25mV
T
A
= -40°C
T
A
= +105°C
2
0
-2
-4
T
A
= +105°C
0
10
20
V+ (V)
T
A
= +85°C
I
OUT
= 0mA
30
40
T
A
= +25°C
T
A
= +85°C
T
A
= +25°C
0
10
20
V+ (V)
30
40
40
0
-6
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Maxim Integrated
│
3
MAX4172-03
1050
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
1.0
OUTPUT ERROR
vs. SUPPLY VOLTAGE
8
C/16 LOAD OUTPUT ERROR
vs. SUPPLY VOLTAGE
MAX4172
Low-Cost, Precision, High-Side
Current-Sense Amplifier
Typical Operating Characteristics (continued)
(V+ = +12V, V
RS+
= 12V, R
OUT
= 1kΩ, T
A
= +25°C, unless otherwise noted.)
ERROR vs. SENSE VOLTAGE
MAX4172-04
35
30
ERROR (%)
30
25
ERROR (%)
20
15
10
5
V
SENSE
= 100mV
25
20
15
10
5
0
-5
0.1m
1m
10m
V
SENSE
(V)
100m
1
0.5V
P-P
1.0V
P-P
5mV
P-P
0.01
0.1
1
10
100
1000
0
POWER-SUPPLY FREQUENCY (kHz)
0.6
OUTPUT ERROR (%)
0.2
-0.2
-0.6
-1.0
-1.4
-1.8
0
4
T
A
= +85°C
V
SENSE
= 100mV
MAX4172-06
2.88
V+ TRIP THRESHOLD (V)
2.78
2.68
2.58
2.48
2.38
T
A
= -40°C
T
A
= +105°C
T
A
= +25°C
8
12
16
V+ (V)
20
24
28
32
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
0 to 10mV V
SENSE
TRANSIENT RESPONSE
0 to 100mV V
SENSE
TRANSIENT RESPONSE
MAX4172-08
MAX4172-09
V
SENSE
5mV/div
GND
V
SENSE
50mV/div
GND
V
OUT
50mV/div
GND
10µs/div
V
OUT
500mV/div
GND
10µs/div
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Maxim Integrated
│
4
MAX4172-07
1.0
OUTPUT ERROR
vs. COMMON MODE VOLTAGE
2.98
V+ THRESHOLD FOR
PG
OUTPUT LOW
vs. TEMPERATURE
MAX4172-05
40
35
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX4172
Low-Cost, Precision, High-Side
Current-Sense Amplifier
Typical Operating Characteristics (continued)
(V+ = +12V, V
RS+
= 12V, R
OUT
= 1kΩ, T
A
= +25°C, unless otherwise noted.)
STARTUP DELAY
MAX4172-10
V+ to
PG
POWER-UP DELAY
MAX4172-11
V
OUT
500mV/div
GND
PG
2V/div
GND
V+
2V/div
GND
5µs/div
V
SENSE
= 100mV
V+
2V/div
GND
10ms/div
100kW PULLUP RESISTOR FROM
PG
TO +4V
Pin Description
PIN
1
2
3, 4
5
6
7
8
NAME
RS+
RS-
N.C.
GND
OUT
PG
V+
FUNCTION
Power connection to the external sense resistor. The “+” indicates the direction of current flow.
Load-side connection for the external sense resistor. The “-” indicates the direction of current flow.
No Connect. No internal connection. Leave open or connect to GND.
Ground
Current Output. OUT is proportional to the magnitude of the sense voltage (V
RS+
- V
RS-
). A 1kΩ
resistor from OUT to ground will result in a voltage equal to 10V/V of sense voltage.
Power Good Open-Collector Logic Output. A low level indicates that V+ is sufficient to power the
MAX4172, and adequate time has passed for power-on transients to settle out.
Supply Voltage Input for the MAX4172
Detailed Description
The MAX4172 is a unidirectional, high-side current-
sense amplifier with an input common-mode range that is
independent of supply voltage. This feature not only
allows the monitoring of current flow into a battery in deep
discharge, but also enables high-side current sensing at
voltages far in excess of the supply voltage (V+).
The MAX4172 current-sense amplifier’s unique topology
simplifies current monitoring and control. The MAX4172’s
amplifier operates as shown in
Figure 1.
The battery/
load current flows through the external sense resistor
(R
SENSE
), from the RS+ node to the RSnode. Current
flows through R
G1
and Q1, and into the current mirror,
where it is multiplied by a factor of 50 before appearing
at OUT.
To analyze the circuit of
Figure 1,
assume that current
flows from RS+ to RS-, and that OUT is connected to
GND through a resistor. Since A1’s inverting input is high
impedance, no current flows though R
G2
(neglecting the
input bias current), so A1’s negative input is equal to
V
SOURCE
- (I
LOAD
x R
SENSE
). A1’s open-loop gain forces
its positive input to essentially the same voltage level as
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