MAX4080,81 Datasheet by Maxim Integrated

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General Description
The MAX4080/MAX4081 are high-side, current-sense
amplifiers with an input voltage range that extends from
4.5V to 76V making them ideal for telecom, automotive,
backplane, and other systems where high-voltage current
monitoring is critical. The MAX4080 is designed for uni-
directional current-sense applications and the MAX4081
allows bidirectional current sensing. The MAX4081 sin-
gle output pin continuously monitors the transition from
charge to discharge and avoids the need for a separate
polarity output. The MAX4081 requires an external refer-
ence to set the zero-current output level (VSENSE = 0V).
The charging current is represented by an output voltage
from VREF to VCC, while discharge current is given from
VREF to GND.
For maximum versatility, the 76V input voltage range
applies independently to both supply voltage (VCC) and
common-mode input voltage (VRS+). High-side current
monitoring does not interfere with the ground path of the
load being measured, making the MAX4080/MAX4081
particularly useful in a wide range of high-voltage sys-
tems.
The combination of three gain versions (5V/V, 20V/V,
60V/V = F, T, S suffix) and a user-selectable, external
sense resistor sets the full-scale current reading and its
proportional output voltage. The MAX4080/MAX4081
offer a high level of integration, resulting in a simple, accu-
rate, and compact current-sense solution.
The MAX4080/MAX4081 operate from a 4.5V to 76V sin-
gle supply and draw only 75µA of supply current. These
devices are specified over the automotive operating tem-
perature range (-40°C to +125°C) and are available in a
space-saving 8-pin µMAX® or SO package.
Applications
Automotive (12V, 24V, or 42V Batteries)
48V Telecom and Backplane Current Measurement
Bidirectional Motor Control
Power-Management Systems
Avalanche Photodiode and PIN-Diode Current
Monitoring
General System/Board-Level Current Sensing
Precision High-Voltage Current Sources
Benefits and Features
Ideal for High-Voltage Current Monitoring Applications
Wide 4.5V to 76V Input Common-Mode Range
Independent Operating Supply Voltage
High Accuracy and Low Quiescent Current Support
Precision Application Requirements
±0.1% Full-Scale Accuracy
Low 100μV Input Offset Voltage
Three Gain Versions Available
- 5V/V (MAX4080F/MAX4081F)
- 20V/V (MAX4080T/MAX4081T)
- 60V/V (MAX4080S/MAX4081S)
75μA Supply Current (MAX4080)
Flexible Current Sensing Supports Monitoring of
Charge and Discharge of Batteries
Bidirectional (MAX4081) or Unidirectional
(MAX4080) ISENSE
Reference Input for Bidirectional OUT (MAX4081)
Minimizes Required Board Space
8-Pin μMAX Package
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
PART TEMP RANGE PIN-PACKAGE
MAX4080FAUA+ -40°C to +125°C 8 µMAX
MAX4080FAUA/V+ -40°C to +125°C 8 µMAX
MAX4080FASA+ -40°C to +125°C 8 SO
MAX4080TAUA+ -40°C to +125°C 8 µMAX
MAX4080TAUA/V+ -40°C to +125°C 8 µMAX
N.C.
OUTGND
1
+
2
8
7
RS-
N.C.VCC
N.C.
RS+
µMAX/SO
TOP VIEW
3
4
6
5
MAX4080
REF1B
OUTGND
1
2
8
7
RS-
REF1AVCC
N.C.
RS+
µMAX/SO
3
4
6
5
MAX4081
+
MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
19-2562; Rev 5; 5/15
Pin Configurations
Ordering Information
EVALUATION KIT AVAILABLE
VCC to GND ..........................................................-0.3V to +80V
RS+, RS- to GND ..................................................-0.3V to +80V
OUT to GND .......... -0.3V to the lesser of +18V or (VCC + 0.3V)
REF1A, REF1B to GND
(MAX4081 Only) -0.3V to the lesser of +18V or (VCC + 0.3V)
Output Short Circuit to GND......................................Continuous
Differential Input Voltage (VRS+ - VRS-) .............................. ±80V
Current into Any Pin .........................................................±20mA
Continuous Power Dissipation (TA = +70°C)
8-Pin ?MAX (derate 4.5mW/°C above +70°C) ............362mW
8-Pin SO (derate 5.88mW/°C above +70°C) ............... 471mW
Operating Temperature Range ......................... -40°C to +125°C
Junction Temperature ...................................................... +150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................. +300°C
Soldering Temperature (reflow) ....................................... +260°C
(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100k, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Operating Voltage Range VCC Inferred from PSRR test 4.5 76 V
Common-Mode Range CMVR Inferred from CMRR test (Note 3) 4.5 76 V
Supply Current ICC VCC = VRS+ = 76V,
no load
MAX4080 75 190 µA
MAX4081 103 190
Leakage Current IRS+, IRS- VCC = 0V, VRS+ = 76V 0.01 2 µA
Input Bias Current IRS+, IRS- VCC = VRS+ = 76V 5 12 µA
Full-Scale Sense Voltage
(Note 4) VSENSE
MAX4080F/MAX4081F ±1000
mVMAX4080T/MAX4081T ±250
MAX4080S/MAX4081S ±100
Gain AV
MAX4080F/MAX4081F 5
V/VMAX4080T/MAX4081T 20
MAX4080S/MAX4081S 60
Gain Accuracy DAV
VCC = VRS+ = 48V
(Note 5)
TA = +25°C±0.1 ±0.6
%TA = -40°C to +85°C±1
TA = TMIN to TMAX ±1.2
Input Offset Voltage VOS
VCC = VRS+ = 48V
(Note 6)
TA = +25°C ±0.1 ±0.6
mVTA = -40°C to +85°C±1
TA = TMIN to TMAX ±1.2
Common-Mode Rejection Ratio
(Note 7) CMRR VCC = 48V, VRS+ = 4.5V to 76V 100 124 dB
Power-Supply Rejection Ratio
(Note 7) PSRR VRS+ = 48V, VCC = 4.5V to 76V 100 122 dB
OUT High Voltage (VCC
VOH)
VCC = 4.5V, VRS+
= 48V, VREF1A =
VREF1B = 2.5V,
IOUT (sourcing) =
+500µA (Note 8)
MAX4080F/MAX4081F,
VSENSE = 1000mV
0.15 0.27 V
MAX4080T/MAX4081T,
VSENSE = 250mV
MAX4080S/MAX4081S,
VSENSE = 100mV
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
DC Electrical Characteristics
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.
Absolute Maximum Ratings
(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100k, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OUT Low Voltage VOL
VCC = VRS+ = 48V,
VREF1A = VREF1B =
2.5V, VSENSE =
-1000mV (for
MAX4081 only)
IOUT (sinking) = 10µA 4 15
IOUT (sinking) = 100µA 23 55
REF1A = REF1B Input Voltage
Range (MAX4081 Only)
(VREF
VGND)
Inferred from REF1A rejection ratio,
VREF1A = VREF1B 1.5 6 V
REF1A Input Voltage Range
(MAX4081 Only)
(VREF1A
VGND)
Inferred from REF1A rejection ratio,
VREF1B = VGND 3 12 V
REF1A Rejection Ratio
(MAX4081 Only)
VCC = VRS+ = 48V, VSENSE = 0V,
VREF1A = VREF1B = 1.5V to 6V 80 108 dB
REF/REF1A Ratio
(MAX4081 Only)
VREF1A = 10V, VREF1B = VGND,
VCC = VRS+ = 48V (Note 2) 0.497 0.500 0.503
REF1A Input Impedance
(MAX4081 Only) VREF1B = VGND 250 k
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
DC Electrical Characteristics (continued)
Note 1: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design.
Note 2: VREF is defined as the average voltage of VREF1A and VREF1B. REF1B is usually connected to REF1A or GND.
VSENSE is defined as VRS+ - VRS-.
Note 3: The common-mode range at the low end of 4.5V applies to the most positive potential at RS+ or RS-. Depending on the
polarity of VSENSE and the device’s gain, either RS+ or RS- can extend below 4.5V by the device’s typical full-scale value of
VSENSE.
Note 4: Negative VSENSE applies to MAX4081 only.
Note 5: VSENSE is:
MAX4080F, 10mV to 1000mV
MAX4080T, 10mV to 250mV
MAX4080S, 10mV to 100mV
MAX4081F, -500mV to +500mV
MAX4081T, -125mV to +125mV
MAX4081S, -50mV to +50mV
Note 6: VOS is extrapolated from the gain accuracy test for the MAX4080 and measured as (VOUT - VREF)/AV at VSENSE = 0V, for
the MAX4081.
Note 7: VSENSE is:
MAX4080F, 500mV
MAX4080T, 125mV
MAX4080S, 50mV
MAX4081F/T/S, 0V
VREF1B = VREF1A = 2.5V
Note 8: Output voltage is internally clamped not to exceed 18V.
Note 9: Output settles to within 1% of final value.
Note 10: The device will not experience phase reversal when overdriven.
(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100k, CLOAD = 20pF,
TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
Bandwidth BW VCC = VRS+ = 48V,
VOUT = 2.5V
MAX4080F/T/S 250 kHz
MAX4081F/T/S 150
OUT Settling Time to 1% of Final
Value
VSENSE = 10mV to 100mV 20 µs
VSENSE = 100mV to 10mV 20
Capacitive-Load Stability No sustained oscillations 500 pF
Output Resistance ROUT VSENSE = 100mV 0.1
Power-Up Time VCC = VRS+ = 48V, VSENSE = 100mV (Note 9) 50 µs
Saturation Recovery Time (Notes 9,10) 50 µs
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
AC Electrical Characteristics
Mmuaus MAxanam Mmaaar MAxoam s MAXADBVT MAxanm F
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)
MAX4080 toc09
FREQUENCY (kHz)
GAIN (dB)
100101
5
10
15
20
25
30
35
40
45
50
0
0.1 1000
MAX4081F/T/S
SMALL-SIGNAL GAIN vs. FREQUENCY
VOUT = 100mVP-P
MAX4081S
MAX4081T
MAX4081F
MAX4080 toc08
FREQUENCY (kHz)
GAIN (dB)
100101
5
10
15
20
25
30
35
40
45
50
0
0.1 1000
MAX4080F/T/S
SMALL-SIGNAL GAIN vs. FREQUENCY
VSENSE = 10mV
MAX4080S
MAX4080T
MAX4080F
MAX4080 toc07
FREQUENCY (Hz)
REFERENCE REJECTION RATIO (dB)
-110
-90
-100
-80
-60
-70
-50
-40
-20
-30
-10
0
-120
MAX4081F/T/S
REFERENCE REJECTION RATIO
vs. FREQUENCY
10k1k100101 100k
MAX4080 toc06
FREQUENCY (Hz)
POWER-SUPPLY REJECTION RATIO (dB)
100k10k1k10010
-120
-100
-110
-90
-80
-60
-70
-50
-40
-20
-30
-10
0
-130
1 1M
MAX4081F/T/S
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX4080 toc05
FREQUENCY (Hz)
COMMON-MODE REJECTION RATIO (dB)
100k10k1k10010
-120
-100
-110
-90
-80
-60
-70
-50
-40
-20
-30
-10
0
-130
1 1M
MAX4081F/T/S
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
GAIN ACCURACY vs. VCC
MAX4080 toc04
VCC (V)
GAIN ACCURACY (%)
6452402816
-0.15
-0.10
-0.05
0
-0.20
4 76
VRS+ = 48V
S VERSION
T VERSION
F VERSION
-0.5
-0.2
-0.3
-0.4
0
-0.1
0.4
0.3
0.2
0.1
0.5
-50 -25 0 25 50 75 100 125
GAIN ACCURACY vs. TEMPERATURE
MAX4080 toc03
TEMPERATURE (°C)
GAIN ACCURACY (%)
INPUT OFFSET VOLTAGE
vs. TEMPERATURE
MAX4080 toc02
-300
-250
-150
-200
0
50
-50
-100
300
100
150
200
250
INPUT OFFSET VOLTAGE (V)
-50 25 500-25 75 100 125 150
TEMPERATURE (°C)
0
20
15
10
5
30
25
35
-125 -75 -50 -25-100 0 25 50 75 100 125
INPUT OFFSET VOLTAGE HISTOGRAM
MAX4080 toc01
INPUT OFFSET VOLTAGE (µV)
PERCENTAGE (%)
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
Typical Operating Characteristics
\\ \ \\ n44 \
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)
MAX4080 toc18
INPUT
5mV/div
OUTPUT
300mV/div
20µs/div
MAX4080S
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc17
INPUT
5mV/div
OUTPUT
100mV/div
20µs/div
MAX4080T
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc16
INPUT
5mV/div
OUTPUT
25mV/div
20µs/div
MAX4080F
SMALL-SIGNAL TRANSIENT RESPONSE
45040035030025020015010050
50
100
150
200
250
300
0
0 500
VOUT LOW VOLTAGE
vs. IOUT (SINKING)
MAX4080 toc15
IOUT (SINKING) (µA)
VOUT LOW VOLTAGE (mV)
TA = +125°C
TA = +85°C
TA = +25°C
TA = 0°C
TA = -40°C
VCC = 4.5V
MAX4080 toc14
IOUT (SOURCING) (mA)
VOUT HIGH VOLTAGE (VCC - VOH) (V)
0.90.80.6 0.70.2 0.3 0.4 0.50.1
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0
0 1.0
VOUT HIGH VOLTAGE
vs. IOUT (SOURCING)
VCC = 4.5V
TA = +125°C
TA = +85°C
TA = +25°C
TA = 0
°
C
TA = -40°C
65
80
75
70
90
85
110
105
100
95
115
-50 -25 0 25 50 75 100 125
MAX4081
SUPPLY CURRENT vs. TEMPERATURE
MAX4080 toc13
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
VREF1A = VREF1B = 2.5V
65
80
75
70
90
85
110
105
100
95
115
-50 -25 0 25 50 75 100 125
MAX4080
SUPPLY CURRENT vs. TEMPERATURE
MAX4080 toc12
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
MAX4080 toc11
VCC (V)
SUPPLY CURRENT (µA)
645216 28 40
85
90
95
100
105
110
115
120
125
4 76
MAX4081
SUPPLY CURRENT vs. VCC
VREF = 2.5V
NO LOAD
VSENSE = 0V
60
65
75
70
80
85
4 2816 40 52 64 76
MAX4080
SUPPLY CURRENT vs. VCC
MAX4080 toc10
VCC (V)
SUPPLY CURRENT (µA)
NO LOAD
VSENSE = 0V
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6
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
Typical Operating Characteristics (continued)
F1 i7, VT Ffi‘ (‘7‘ f1 f7 VT
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)
MAX4080 toc27
INPUT
33mV/div
OUTPUT
2V/div
20µs/div
MAX4081S
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc26
INPUT
100mV/div
OUTPUT
2V/div
20µs/div
MAX4081T
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc25
INPUT
400mV/div
OUTPUT
2V/div
20µs/div
MAX4081F
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc24
INPUT
33mV/div
OUTPUT
2V/div
20µs/div
MAX4080S
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc23
INPUT
100mV/div
OUTPUT
2V/div
20µs/div
MAX4080T
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc22
INPUT
400mV/div
OUTPUT
2V/div
20µs/div
MAX4080F
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc21
INPUT
1mV/div
OUTPUT
50mV/div
20µs/div
MAX4081S
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc20
INPUT
2.5mV/div
OUTPUT
50mV/div
20µs/div
MAX4081T
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc19
INPUT
10mV/div
OUTPUT
50mV/div
20µs/div
MAX4081F
SMALL-SIGNAL TRANSIENT RESPONSE
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
Typical Operating Characteristics (continued)
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)
MAX4080 toc30
VCC
(0 TO 10V)
5V/div
OUTPUT
2.5V/div
100µs/div
MAX4080T
STARTUP DELAY
(VSENSE = 250mV)
MAX4080 toc29
INPUT
500mV/div
OUTPUT
2V/div
20µs/div
MAX4080F
SATURATION RECOVERY RESPONSE
(VCC = 4.5V)
MAX4080 toc28
4µs/div
VCC-TRANSIENT RESPONSE
VCC
5V/div
VOUT
1V/div
VRS+ = 20V
VCC = 20V STEP
VREF1 = VREF2 = 2.5V
VCC = 40V
VCC = 20V
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
Typical Operating Characteristics (continued)
Detailed Description
The MAX4080/MAX4081 unidirectional and bidirectional
high-side, current-sense amplifiers feature a 4.5V to 76V
input common-mode range that is independent of supply
voltage. This feature allows the monitoring of current out
of a battery as low as 4.5V and also enables high-side cur-
rent sensing at voltages greater than the supply voltage
(VCC). The MAX4080/MAX4081 monitors current through
a current-sense resistor and amplifies the voltage across
the resistor. The MAX4080 senses current unidirectional-
ly, while the MAX4081 senses current bidirectionally.
The 76V input voltage range of the MAX4080/MAX4081
applies independently to both supply voltage (VCC) and
common-mode, input-sense voltage (VRS+). High-side
current monitoring does not interfere with the ground
path of the load being measured, making the MAX4080/
MAX4081 particularly useful in a wide range of high-volt-
age systems.
Battery-powered systems require a precise bidirectional
current-sense amplifier to accurately monitor the battery’s
charge and discharge. The MAX4081 charging current
is represented by an output voltage from VREF to VCC,
while discharge current is given from VREF to GND.
Measurements of OUT with respect to VREF yield a posi-
tive and negative voltage during charge and discharge, as
illustrated in Figure 1 for the MAX4081T.
Current Monitoring
The MAX4080 operates as follows: current from the
source flows through RSENSE to the load (Figure 2), cre-
ating a sense voltage, VSENSE. 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 ampli-
fier’s open-loop gain forces its noninverting input to the
same voltage as the inverting input. Therefore, the drop
across RG1 equals VSENSE. The internal current mirror
multiplies IRG1 by a current gain factor, β, to give IA2 =
β × IRG1. Amplifier A2 is used to convert the output
current to a voltage and then sent through amplifier
A3. Total gain = 5V/V for MAX4080F, 20V/V for the
MAX4080T, and 60V/V for the MAX4080S.
The MAX4081 input stage differs slightly from the
MAX4080 (Figure 3). Its topology allows for monitoring
of bidirectional currents through the sense resistor. When
current flows from RS+ to RS-, the MAX4081 matches the
voltage drop across the external sense resistor, RSENSE,
by increasing the current through the Q1 and RG1. In this
way, the voltages at the input terminals of the internal
amplifier A1 are kept constant and an accurate measure-
ment of the sense voltage is achieved. In the following
amplifier stages of the MAX4081, the output signal of
amplifier A2 is level- shifted to the reference voltage
(VREF = VREF1A = VREF1B), resulting in a voltage at the
output pin (OUT)
PIN NAME FUNCTION
MAX4080 MAX4081
1 1 RS+ Power connection to the external-sense resistor.
2 2 VCC Supply Voltage Input. Decouple VCC to GND with at least a 0.1µF capacitor to
bypass line transients.
3, 6, 7 3 N.C. No Connection. No internal connection. Leave open or connect to ground.
4 4 GND Ground
5 5 OUT
Voltage Output. For the unidirectional MAX4080, VOUT is proportional to
VSENSE. For the bidirectional MAX4081, the difference voltage (VOUT - VREF) is
proportional to VSENSE and indicates the correct polarity.
8 8 RS- Load connection to the external sense resistor.
6 REF1B Reference Voltage Input: Connect REF1B to REF1A or to GND (see the External
Reference section).
7 REF1A
Reference Voltage Input: Connect REF1A and REF1B to a fixed reference
voltage (VREF). VOUT is equal to VREF when VSENSE is zero (see the External
Reference section).
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MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
Pin Description
%
that swings above VREF voltage for positive-sense volt-
ages and below VREF for negative-sense voltages.
VOUT is equal to VREF when VSENSE is equal to zero.
Set the full-scale output range by selecting RSENSE
and the appropriate gain version of the MAX4080/
MAX4081.
Note: For Gain = 5 (F), RG1 = RG2 = 160k.
For Gain = 20 (T), RG1 = RG2 = 60k.
For Gain = 60 (S), RG1 = RG2 = 20k.
Figure 3. MAX4081 Functional DiagramFigure 2. MAX4080 Functional Diagram
Figure 1. MAX4081T OUT Transfer Curve
VSENSE
RG1 RG2
VREF
RS-
REF1B
OUT
GND
REF1A
Q1 Q2
RF
125k
125k
RS+
CURRENT
MIRROR
CURRENT
MIRROR
A1
A2
MAX4081
RSENSE
VSENSE
ILOAD
OUT
RG1 RG2
RS-
Q1
RS+
CURRENT
MIRROR
A1
IA2
A3A2
MAX4080
MAX4081T
VSENSE ICHARGE
ILOAD
RSENSE
VCC
GND
RS+RS-
OUT
REF1A
REF1B
5V
SYSTEM LOAD
AND CHARGER
BATTERY
VOUT = VGND
VOUT = 10V
VREF1A = VREF1B = 5V
DISCHARGE CURRENT
4.5V TO 76V
VOUT - VREF
CHARGE CURRENT
5V
10V
-250mV 250mV
-5V
VSENSE
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10
MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
External References (MAX4081)
For the bidirectional MAX4081, the VOUT reference level
is controlled by REF1A and REF1B. VREF is defined as
the average voltage of VREF1A and VREF1B. Connect
REF1A and REF1B to a low-noise, regulated voltage
source to set the output reference level. In this mode,
VOUT equals VREF1A when VSENSE equals zero (see
Figure 4).
Alternatively, connect REF1B to ground, and REF1A to a
low-noise, regulated voltage source. In this case, the out-
put reference level (VREF) is equal to VREF1A divided by
two. VOUT equals VREF1A/2 when VSENSE equals zero.
In either mode, the output swings above the reference
voltage for positive current-sensing (VRS+ > VRS-). The
output swings below the reference voltage for negative
current-sensing (VRS+ < VRS-).
Applications Information
Recommended Component Values
Ideally, the maximum load current develops the full-scale
sense voltage across the current-sense resistor. Choose
the gain needed to yield the maximum output voltage
required for the application:
VOUT = VSENSE 5 AV
where VSENSE is the full-scale sense voltage, 1000mV
for gain of 5V/V, 250mV for gain of 20V/V, 100mV for gain
of 60V/V, and AV is the gain of the device.
In applications monitoring a high current, ensure that
RSENSE is able to dissipate its own I2R loss. If the resis-
tor’s power dissipation is exceeded, its value may drift or
it may fail altogether.
The MAX4080/MAX4081 sense a wide variety of currents
with different sense-resistor values. Table 1 lists common
resistor values for typical operation.
Table 1. Typical Component Values
FULL-SCALE LOAD
CURRENT, ILOAD (A)
CURRENT-SENSE
RESISTOR (m)
GAIN
(V/V)
FULL-SCALE
VSENSE
(mV)
MAX4081 FULL-SCALE
OUTPUT VOLTAGE
(VOUT - VREF, V)
0.500 1000 5 ±500 ±2.5
0.125 1000 20 ±125 ±2.5
0.050 1000 60 ±50 ±3.0
5.000 100 5 ±500 ±2.5
1.250 100 20 ±125 ±2.5
0.500 100 60 ±50 ±3.0
50.000 10 5 ±500 ±2.5
12.500 10 20 ±125 ±2.5
5.000 10 60 ±50 ±3.0
FULL-SCALE LOAD
CURRENT, ILOAD (A)
CURRENT-SENSE
RESISTOR (m)
GAIN
(V/V)
FULL-SCALE
VSENSE
(mV)
MAX4080 FULL-SCALE
OUTPUT VOLTAGE (V)
1.000 1000 5 1000 5.0
0.250 1000 20 250 5.0
0.100 1000 60 100 6.0
10.000 100 5 1000 5.0
2.500 100 20 250 5.0
1.000 100 60 100 6.0
50.000 10 5 500 2.5
25.000 10 20 250 5.0
10.000 10 60 100 6.0
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11
MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
‘ “if H} m7 NJ ‘WOJ “"D’ “H
The full-scale output voltage is VOUT = RSENSE × ILOAD
(MAX) × AV, for the MAX4080 and VOUT = VREF ± RSENSE
× ILOAD(MAX) × AV for the MAX4081. VSENSE(MAX) is
1000mV for the 5V/V gain version, 250mV for the 20V/V
gain version, and 100mV for the 60V/V gain version.
Choosing the Sense Resistor
Choose RSENSE based on the following criteria:
Voltage Loss: A high RSENSE value causes the pow-
er-source voltage to degrade through IR loss. For minimal
voltage loss, use the lowest RSENSE value.
Accuracy: A high RSENSE value allows lower cur-
rents to be measured more accurately. This is due
to offsets becoming less significant when the sense
voltage is larger. For best performance, select
RSENSE to provide approximately 1000mV (gain of
5V/V), 250mV (gain of 20V/V), or 100mV (gain of
60V/V) of sense voltage for the full-scale current in
each application.
Efficiency and Power Dissipation: At high current
levels, the I2R losses in RSENSE can be significant.
Take this into consideration when choosing the resis-
tor value and its power dissipation (wattage) rating.
Also, the sense resistor’s value might drift if it is
allowed to heat up excessively.
Inductance: Keep inductance low if ISENSE has a
large high-frequency component. Wire-wound resis-
tors have the highest inductance, while metal film is
somewhat better. Low-inductance, metal-film resistors
are also available. Instead of being spiral- wrapped
around a core, as in metal-film or wire-wound resis-
tors, they are a straight band of metal and are avail-
able in values under 1.
Because of the high currents that flow through RSENSE,
take care to eliminate parasitic trace resistance from
causing errors in the sense voltage. Either use a four-ter-
minal current-sense resistor or use Kelvin (force and
sense) PC board layout techniques.
Dynamic Range Consideration
Although the MAX4081 have fully symmetrical bidirec-
tional VSENSE input capability, the output voltage range
is usually higher from REF to VCC and lower from REF
to GND (unless the supply voltage is at the lowest end of
the operating range). Therefore, the user must consider
the dynamic range of current monitored in both directions
and choose the supply voltage and the reference voltage
(REF) to make sure the output swing above and below
REF is adequate to handle the swings without clipping or
running out of headroom.
Power-Supply Bypassing and Grounding
For most applications, bypass VCC to GND with a 0.1µF
ceramic capacitor. In many applications, VCC can be
connected to one of the current monitor terminals (RS+
or RS-). Because VCC is independent of the monitored
voltage, VCC can be connected to a separate regulated
supply.
If VCC will be subject to fast-line transients, a series
resistor can be added to the power-supply line of the
MAX4080/MAX4081 to minimize output disturbance. This
resistance and the decoupling capacitor reduce the rise
time of the transient. For most applications, 1k in con-
junction with a 0.1µF bypass capacitor work well.
The MAX4080/MAX4081 require no special consider-
ations with respect to layout or grounding. Consideration
should be given to minimizing errors due to the large
charge and discharge currents in the system.
Figure 4. MAX4081 Reference Inputs
MAX4081
RSENSE
ILOAD = 0
LOAD
VCC
GND
RS-RS+
OUT
REF1A
REF1B
5V
5V
10V
MAX4081
RSENSE
ILOAD = 0
LOAD
VCC
GND
RS-RS+
OUT
REF1A
REF1B
5V
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12
MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
+Denmes a Iead(Pb)rIree/ROHSrcomp/Ia"I package.
Power Management
The bidirectional capability of the MAX4081 makes it an
excellent candidate for use in smart battery packs. In the
application diagram (Figure 5), the MAX4081 monitors the
charging current into the battery as well as the discharge
current out of the battery. The microcontroller stores this
information, allowing the system to query the battery’s
status as needed to make system power-management
decisions.
+Denotes a lead(Pb)-free/RoHS-compliant package.
Figure 5. MAX4081 Used In Smart-Battery Application
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 µMAX U8+1 21-0036 90-0092
8 SO S8+2 21-0041 90-0096
PART TEMP RANGE PIN-PACKAGE
MAX4080TASA+ -40°C to +125°C 8 SO
MAX4080SAUA+ -40°C to +125°C 8 µMAX
MAX4080SAUA/V+ -40°C to +125°C 8 µMAX
MAX4080SASA+ -40°C to +125°C 8 SO
MAX4081FAUA+ -40°C to +125°C 8 µMAX
MAX4081FASA+ -40°C to +125°C 8 SO
MAX4081TAUA+ -40°C to +125°C 8 µMAX
MAX4081TASA+ -40°C to +125°C 8 SO
MAX4081SAUA+ -40°C to +125°C 8 µMAX
MAX4081SASA+ -40°C to +125°C 8 SO
PART GAIN (V/V) ISENSE
MAX4080FAUA 5 Unidirectional
MAX4080FASA 5 Unidirectional
MAX4080TAUA 20 Unidirectional
MAX4080TASA 20 Unidirectional
MAX4080SAUA 60 Unidirectional
MAX4080SASA 60 Unidirectional
MAX4081FAUA 5 Bidirectional
MAX4081FASA 5 Bidirectional
MAX4081TAUA 20 Bidirectional
MAX4081TASA 20 Bidirectional
MAX4081SAUA 60 Bidirectional
MAX4081SASA 60 Bidirectional
MAX4080
VCC = 4.5V TO 76V
RSENSE
ISENSE
SYSTEM
LOAD
VCC
GND
RS-RS+
OUT
MAX4081
RSENSE
VCC
GND
RS-RS+
OUT
REF1A
REF1B
SYSTEM
POWER
MANAGEMENT
AND
CHARGER
CIRCUITRY
µC
1.8V
SERIAL
INTERFACE
BATTERY
MAX1243
ADC
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13
MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.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.
Ordering Information (continued)
Chip Information
PROCESS: Bipolar
Typical Operating Circuit
Selector Guide
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 10/02 Initial release
1 11/08 Added values for RG1 and RG2 10
2 5/09 Added lead-free and automotive parts to Ordering Information 1
3 5/10 Removed automotive part and added soldering temperature 1, 2
4 7/11 Added automotive part designation 1
5 5/15 Updated Benefits and Features section 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated 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.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2015 Maxim Integrated Products, Inc.
14
MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers
with Voltage Output
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

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