Bidirectional, Zero Drift,
Current Sense Amplifier
AD8417
Data Sheet
FEATURES
GENERAL DESCRIPTION
Typical 0.1 µV/°C offset drift
Maximum ±400 µV voltage offset over full temperature range
2.7 V to 5.5 V power supply operating range
EMI filters included
High common-mode input voltage range
−2 V to +70 V continuous
−3 V to +80 V survival
Initial gain = 60 V/V
Wide operating temperature range
AD8417WB (8-lead MSOP, 8-lead SOIC_N, and 10-lead
MSOP) and AD8417B (8-lead MSOP): −40°C to +125°C
AD8417WH (8-lead SOIC_N and 8-lead MSOP):
−40°C to +150°C
Bidirectional operation
Available in 8-lead SOIC_N, 8-lead MSOP, and FMEA tolerant
10-lead MSOP pinout
CMRR: 86 dB, dc to 10 kHz
AEC-Q100 qualified for automotive applications
The AD8417 is a high voltage, high resolution current sense
amplifier. It features an initial gain of 60 V/V, with a maximum
±0.3% gain error over the entire temperature range. The buffered
output voltage directly interfaces with any typical converter.
The AD8417 offers excellent input common-mode rejection
from −2 V to +70 V. The AD8417 performs bidirectional current
measurements across a shunt resistor in a variety of automotive
and industrial applications, including motor control, power
management, and solenoid control.
The AD8417 offers breakthrough performance throughout the
−40°C to +150°C temperature range (AD8417WH). It features
a zero drift core, which leads to a typical offset drift of 0.1 µV/°C
throughout the operating temperature range and the commonmode voltage range. The AD8417 is qualified for automotive
applications. The device includes electromagnetic interference
(EMI) filters and patented (U.S. Patent 8,624,668 B2) circuitry
to enable output accuracy with pulse-width modulation (PWM)
type input common-mode voltages. The typical input offset voltage
is ±200 µV. The AD8417 is offered in 8-lead MSOP and 8-lead
SOIC_N, along with a 10-lead MSOP pinout option engineered
for failure mode and effects analysis (FMEA).
APPLICATIONS
High-side current sensing in
Motor controls
Solenoid controls
Power management
Low-side current sensing
Diagnostic protection
Table 1. Related Devices
Part No.
AD8205
AD8206
AD8207
AD8210
AD8418
Description
Current sense amplifier, gain = 50
Current sense amplifier, gain = 20
High accuracy current sense amplifier, gain = 20
High speed current sense amplifier, gain = 20
High accuracy current sense amplifier, gain = 20
TYPICAL APPLICATION CIRCUIT
VCM = –2V TO +70V
VS = 2.7V TO 5.5V
70V
VS
VREF 1
AD8417
VCM
+IN
ISHUNT
EMI
FILTER
OUT
G = 60
RSHUNT
50A
VOUT
+
0V
–IN
VS
VS/2
EMI
FILTER
–
ISHUNT
–50A
VREF 2
11882-001
0V
GND
Figure 1.
Rev. E
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AD8417
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Bidirectional Operation ............................................................ 11
Applications ...................................................................................... 1
External Referenced Output ..................................................... 12
General Description ......................................................................... 1
Splitting the Supply .................................................................... 12
Typical Application Circuit ............................................................ 1
Splitting an External Reference ................................................ 12
Revision History ............................................................................... 2
Applications Information ............................................................. 13
Specifications..................................................................................... 3
Motor Control ............................................................................ 13
Absolute Maximum Ratings ........................................................... 4
Solenoid Control ........................................................................ 14
ESD Caution.................................................................................. 4
Pinout Option Engineered for FMEA ..................................... 15
Pin Configurations and Function Descriptions ........................... 5
Outline Dimensions ....................................................................... 16
Typical Performance Characteristics ............................................. 6
Ordering Guide .......................................................................... 17
Theory of Operation ...................................................................... 10
Automotive Products ................................................................ 17
Output Offset Adjustment ............................................................ 11
Unidirectional Operation.......................................................... 11
REVISION HISTORY
3/2020—Rev. D to Rev. E
Added 10-Lead MSOP ................................................................ Universal
Changed AD8417WB to AD8417WB and AD8417B, and
Patented to Patented (U.S. Patent 8,624,668 B2) ...... Throughout
Changes to Features Section and General Description Section ...... 1
Changed Functional Block Diagram Section to Typical
Application Circuit Section............................................................. 1
Changes to Figure 2 and Table 4 Caption ..................................... 5
Added Figure 3; Renumbered Sequentially and Table 5;
Renumbered Sequentially ............................................................... 5
Changes to Figure 11 to Figure 15 ................................................. 7
Changes to Figure 16 to Figure 19 ................................................. 8
Change to Figure 23 ......................................................................... 9
Deleted Figure 26; Renumbered Sequentially ............................ 10
Added Pinout Option Engineered for FMEA Section and
Table 6 .............................................................................................. 15
Updated Outline Dimensions ....................................................... 17
Changes to Ordering Guide .......................................................... 17
6/2019—Rev. C to Rev. D
Changes to Features Section ............................................................1
Changes to Table 3 ............................................................................4
Changes to Figure 33 ..................................................................... 13
10/2017—Rev. B to Rev. C
Change to Splitting an External Reference Section ................... 12
4/2015—Rev. A to Rev. B
Change to Figure 36 ....................................................................... 14
11/2014—Rev. 0 to Rev. A
Added AD8417WH ...........................................................Universal
Changes to Features Section and General Description Section ........1
Changes to Specifications Section and Table 2 .............................3
Changes to Table 3 ............................................................................4
Changes to Ordering Guide .......................................................... 16
11/2013—Revision 0: Initial Version
Rev. E | Page 2 of 17
Data Sheet
AD8417
SPECIFICATIONS
TA = −40°C to +125°C (operating temperature range) for the AD8417WB and AD8417B, TA = −40°C to +150°C for the AD8417WH,
VS = 5 V, unless otherwise noted.
Table 2.
Parameter
GAIN
Initial
Error Over Temperature
Gain vs. Temperature
VOLTAGE OFFSET
Offset Voltage, Referred to the Input (RTI)
Over Temperature, RTI
Offset Drift
INPUT
Input Bias Current
Input Voltage Range
Common-Mode Rejection Ratio (CMRR)
OUTPUT
Output Voltage Range
Output Resistance
DYNAMIC RESPONSE
Small Signal −3 dB Bandwidth
Slew Rate
NOISE
0.1 Hz to 10 Hz, RTI
Spectral Density, 1 kHz, RTI
OFFSET ADJUSTMENT
Ratiometric Accuracy1
Accuracy, Referred to the Output (RTO)
Output Offset Adjustment Range
POWER SUPPLY
Operating Range
Quiescent Current Over Temperature
Test Conditions/Comments
Typ
Max
Unit
±0.3
+10
V/V
%
ppm/°C
±400
+0.4
µV
µV
µV/°C
60
Specified temperature range
−10
25°C
Specified temperature range
±200
−0.4
+0.1
130
Common mode, continuous
Specified temperature range, f = dc
f = dc to 10 kHz
−2
90
RL = 25 kΩ
0.045
Divider to supplies
Voltage applied to VREF1 and VREF2 in parallel
VS = 5 V
0.499
+70
100
86
VS − 0.035
2
V
Ω
250
1
kHz
V/µs
2.3
110
µV p-p
nV/√Hz
0.045
V/V
mV/V
V
2.7
5.5
V
4.1
4.2
mA
mA
dB
+125
+150
°C
°C
80
AD8417WB and AD8417B
AD8417WH
−40
−40
The offset adjustment is ratiometric to the power supply when VREF1 and VREF2 are used as a divider between the supplies.
Rev. E | Page 3 of 17
µA
V
dB
dB
0.501
±1
VS − 0.035
VOUT = 0.1 V dc
AD8417WB and AD8417B
AD8417WH
Power Supply Rejection Ratio
Temperature Range
For Specified Performance
Operating Temperature Range
1
Min
AD8417
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter
Supply Voltage
Input Voltage Range
Survival Common-Mode
Differential
Reverse Supply Voltage
ESD Human Body Model (HBM)
Operating Temperature Range
AD8417WB and AD8417B
AD8417WH
Storage Temperature Range
Output Short-Circuit Duration
Rating
6V
−3 V to +80 V
5.5 V (magnitude)
0.3 V
±2000 V
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
ESD CAUTION
−40°C to +125°C
−40°C to +150°C
−65°C to +150°C
Indefinite
Rev. E | Page 4 of 17
Data Sheet
AD8417
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
+IN
7
VREF 2 3
VREF 1
TOP VIEW
(Not to Scale)
6
VS
5
OUT
NC 4
11882-002
8
AD8417
–IN 1
GND 2
NOTES
1. NC = NO CONNECT. DO NOT
CONNECT TO THIS PIN.
Figure 2. 8-Lead MSOP and 8-Lead SOIC_N Pin Configuration
Table 4. 8-Lead MSOP and 8-Lead SOIC_N Pin Function Descriptions
Mnemonic
−IN
GND
VREF2
NC
OUT
VS
VREF1
+IN
Description
Negative Input.
Ground.
Reference Input 2.
No Connect. Do not connect to this pin.
Output.
Supply.
Reference Input 1.
Positive Input.
–IN 1
10
+IN
NC 2
AD8417-10
9
NC
GND 3
TOP VIEW
(Not to Scale)
8
VREF 1
7
VS
6
OUT
VREF 2 4
NC 5
NOTES
1. NC = NO CONNECT. DO NOT
CONNECT TO THIS PIN.
11882-303
Pin No.
1
2
3
4
5
6
7
8
Figure 3. 10-Lead MSOP Pin Configuration
Table 5. 10-Lead MSOP Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
Mnemonic
−IN
NC
GND
VREF2
NC
OUT
VS
VREF1
NC
+IN
Description
Negative Input.
No Connect. Do not connect to this pin.
Ground.
Reference Input 2.
No Connect. Do not connect to this pin.
Output.
Supply.
Reference Input 1.
No Connect. Do not connect to this pin.
Positive Input.
Rev. E | Page 5 of 17
AD8417
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
50
14
40
12
20
GAIN (dB)
OFFSET VOLTAGE (µV)
30
10
8
6
10
0
–10
4
–20
2
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
–40
1000
11882-003
0
–40
100k
10k
10M
1M
FREQUENCY (Hz)
Figure 4. Typical Offset Voltage Drift vs. Temperature
11882-006
–30
Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p)
10
120
9
TOTAL OUTPUT ERROR (%)
110
CMRR (dB)
100
90
80
70
8
7
6
5
4
3
2
60
1k
100
10k
1M
100k
FREQUENCY (Hz)
0
11882-004
50
10
0
5
10
15
20
25
30
35
40
DIFFERENTIAL INPUT VOLTAGE (mV)
Figure 5. Typical CMRR vs. Frequency
11882-007
1
Figure 8. Total Output Error vs. Differential Input Voltage
500
0.5
NORMALIZED AT 25°C
400
BIAS CURRENT PER INPUT PIN (mA)
0.4
200
100
0
–100
–200
–300
–400
0.3
+IN
0.2
0.1
0
–IN
–0.1
–0.2
–0.3
–0.4
–25
–10
5
20
35
50
65
80
95
TEMPERATURE (°C)
110
125
Figure 6. Typical Gain Error vs. Temperature
VS = 2.7V
–0.5
–4 0
4
8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68
VCM (V)
Figure 9. Bias Current per Input Pin vs. VCM
Rev. E | Page 6 of 17
11882-008
–500
–40
11882-005
GAIN ERROR (µV/V)
300
Data Sheet
AD8417
4.5
VS = 5V
VS = 2.7V
10mV/DIV
3.5
INPUT
3.0
2.5
500mV/DIV
2.0
1.5
VS = 2.7V
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70
INPUT COMMON-MODE VOLTAGE (V)
11882-009
1.0
–5
TIME (1µs/DIV)
11882-012
OUTPUT
Figure 13. Fall Time (VS = 2.7 V)
Figure 10. Supply Current vs. Input Common-Mode Voltage
INPUT
25mV/DIV
10mV/DIV
INPUT
1V/DIV
OUTPUT
OUTPUT
VS = 5V
11882-010
VS = 2.7V
TIME (1µs/DIV)
TIME (1µs/DIV)
Figure 11. Rise Time (VS = 2.7 V)
11882-013
500mV/DIV
Figure 14. Fall Time (VS = 5 V)
INPUT
INPUT
50mV/DIV
25mV/DIV
OUTPUT
OUTPUT
1V/DIV
VS = 5V
TIME (1µs/DIV)
VS = 2.7V
TIME (1µs/DIV)
Figure 12. Rise Time (VS = 5 V)
11882-014
2V/DIV
11882-011
SUPPLY CURRENT (mA)
4.0
Figure 15. Differential Overload Recovery, Rising (VS = 2.7 V)
Rev. E | Page 7 of 17
AD8417
Data Sheet
INPUT
100mV/DIV
OUTPUT
100mV/DIV
OUTPUT
INPUT COMMON MODE
2.5V/DIV
VS = 5V
11882-015
VS = 5V
TIME (1µs/DIV)
11882-018
40V/DIV
TIME (4 µs/DIV)
Figure 19. Input Common-Mode Step Response (VS = 5 V, Inputs Shorted)
Figure 16. Differential Overload Recovery, Rising (VS = 5 V)
50mV/DIV
INPUT
2V/DIV
VS = 2.7V
TIME (1µs/DIV)
11882-016
OUTPUT
40
35
30
5V
25
2.7V
20
15
10
5
0
–40
Figure 17. Differential Overload Recovery, Falling (VS = 2.7 V)
–25
–10
5
20
35
50
65
80
95
110
125
11882-019
MAXIMUM OUTPUT SINK CURRENT (mA)
45
Figure 20. Maximum Output Sink Current vs. Temperature
100mV/DIV
INPUT
2.5V/DIV
VS = 5V
TIME (1µs/DIV)
11882-017
OUTPUT
35
30
5V
25
2.7V
20
15
10
5
0
–40
Figure 18. Differential Overload Recovery, Falling (VS = 5 V)
–25
–10
5
20
35
50
65
80
95
110
125
Figure 21. Maximum Output Source Current vs. Temperature
Rev. E | Page 8 of 17
11882-020
MAXIMUM OUTPUT SOURCE CURRENT (mA)
40
Data Sheet
AD8417
0.15
0
NORMALIZED AT 25°C
OUTPUT VOLTAGE RANGE FROM
POSITIVE RAIL (mV)
–50
0.10
–100
–150
CMRR (µV/V)
0.05
–200
–250
–300
0
–0.05
–350
–400
–0.10
0
1
2
3
4
5
6
7
8
9
10
OUTPUT SOURCE CURRENT (mA)
–0.15
–40
–25
–10
Figure 22. Output Voltage Range from Positive Rail vs. Output Source Current
5
20
35
50
65
80
95
110
125
11882-024
–500
11882-021
–450
Figure 25. CMRR vs. Temperature
300
250
2100
1800
200
1500
HITS
OUTPUT VOLTAGE RANGE FROM
GROUND (mV)
2400
150
1200
900
100
600
50
0
1
2
4
3
5
6
7
9
8
10
OUTPUT SINK CURRENT (mA)
Figure 23. Output Voltage Range from Ground vs. Output Sink Current
1800
1500
–40°C
+25°C
+125°C
900
600
300
0
–400
–300
–200
–100
0
100
200
VOSI WITH VCC = 5.0V (µV)
300
400
11882-023
HITS
1200
Figure 24. Offset Voltage Distribution
Rev. E | Page 9 of 17
0
–8
–6
–4
–2
0
2
4
GAIN ERROR DRIFT (ppm/°C)
Figure 26. Gain Error Drift Distribution
6
8
11882-125
0
11882-022
300
AD8417
Data Sheet
THEORY OF OPERATION
The AD8417 is a single-supply, zero drift, difference amplifier
that uses a unique architecture to accurately amplify small
differential current shunt voltages in the presence of rapidly
changing common-mode voltages.
In typical applications, the AD8417 measures current by
amplifying the voltage across a shunt resistor connected to its
inputs by a gain of 60 V/V (see Figure 1).
The AD8417 design provides excellent common-mode
rejection, even with PWM common-mode inputs that can
change at very fast rates, for example, 1 V/ns. The AD8417
contains patented (U.S. Patent 8,624,668 B2) technology to
eliminate the negative effects of such fast changing external
common-mode variations.
The AD8417 features an input offset drift of less than
0.4 µV/°C. This performance is achieved through a novel zero
drift architecture that does not compromise bandwidth, which
is typically rated at 250 kHz.
The reference inputs, VREF1 and VREF2, are tied through 100 kΩ
resistors to the positive input of the main amplifier, which allows
the output offset to be adjusted anywhere in the output operating
range. The gain is 1 V/V from the reference pins to the output
when the reference pins are used in parallel. When the pins are
used to divide the supply, the gain is 0.5 V/V.
The AD8417 offers breakthrough performance without
compromising any of the robust application needs typical of
solenoid or motor control. The ability to reject PWM input
common-mode voltages and the zero drift architecture
providing low offset and offset drift allows the AD8417 to
deliver total accuracy for these demanding applications.
Rev. E | Page 10 of 17
Data Sheet
AD8417
The output of the AD8417 can be adjusted for unidirectional or
bidirectional operation.
UNIDIRECTIONAL OPERATION
Unidirectional operation allows the AD8417 to measure
currents through a resistive shunt in one direction. The basic
modes for unidirectional operation are ground referenced
output mode and VS referenced output mode.
VS Referenced Output Mode
VS referenced output mode is set when both reference pins are
tied to the positive supply. It is typically used when the diagnostic
scheme requires detection of the amplifier and the wiring
before power is applied to the load (see Figure 28).
VS
For unidirectional operation, the output can be set at the negative
rail (near ground) or at the positive rail (near VS) when the
differential input is 0 V. The output moves to the opposite rail
when a correct polarity differential input voltage is applied. The
required polarity of the differential input depends on the output
voltage setting. If the output is set at the positive rail, the input
polarity must be negative to decrease the output. If the output is
set at ground, the polarity must be positive to increase the
output.
AD8417
R4
–IN
+
R2
VREF 1
R3
VREF 2
GND
BIDIRECTIONAL OPERATION
Bidirectional operation allows the AD8417 to measure currents
through a resistive shunt in two directions.
In this case, the output is set anywhere within the output range.
Typically, it is set at half scale for equal range in both directions.
In some cases, however, it is set at a voltage other than half
scale when the bidirectional current is nonsymmetrical.
VS
AD8417
R4
–
Apply voltage(s) to the referenced inputs to adjust the output.
VREF1 and VREF2 are tied to internal resistors that connect to an
internal offset node. There is no operational difference between
the pins.
OUT
+
+IN
OUT
Figure 28. VS Referenced Output
When using the AD8417 in ground referenced output mode,
both referenced inputs are tied to ground, which causes the
output to sit at the negative rail when there are zero differential
volts at the input (see Figure 27).
R1
–
+IN
Ground Referenced Output Mode
–IN
R1
11882-026
OUTPUT OFFSET ADJUSTMENT
R2
VREF 1
R3
VREF 2
11882-025
GND
Figure 27. Ground Referenced Output
Rev. E | Page 11 of 17
AD8417
Data Sheet
EXTERNAL REFERENCED OUTPUT
VS
Tying both pins together and to a reference produces an output
equal to the reference voltage when there is no differential input
(see Figure 29). The output decreases the reference voltage when
the input is negative, relative to the −IN pin, and increases when
the input is positive, relative to the −IN pin.
AD8417
R4
–IN
R1
–
OUT
+
+IN
R2
VS
VREF 1
R3
VREF 2
R4
–IN
R1
GND
–
OUT
Figure 30. Split Supply
+
+IN
11882-028
AD8417
R2
SPLITTING AN EXTERNAL REFERENCE
VREF 1
R3
VREF 2
11882-027
2.5V
GND
Use the internal reference resistors to divide an external reference
by 2 with an accuracy of approximately 0.2%. Split an external
reference by connecting one VREFx pin to ground and the other
VREFx pin to the reference (see Figure 31).
Figure 29. External Referenced Output
VS
SPLITTING THE SUPPLY
AD8417
R4
–IN
R1
–
OUT
+
+IN
R2
VREF 1
R3
VREF 2
GND
Figure 31. Split External Reference
Rev. E | Page 12 of 17
5V
11882-029
By tying one reference pin to VS and the other to GND, the output
is set at half of the supply when there is no differential input (see
Figure 30). The benefit of this configuration is that an external
reference is not required to offset the output for bidirectional
current measurement. Tying one reference pin to VS and the
other to GND creates a midscale offset that is ratiometric to the
supply, which means that if the supply increases or decreases,
the output remains at half the supply. For example, if the supply
is 5.0 V, the output is at half scale, or 2.5 V. If the supply increases
by 10% (to 5.5 V), the output increases to 2.75 V.
Data Sheet
AD8417
MOTOR CONTROL
3-Phase Motor Control
The AD8417 is ideally suited for monitoring current in 3-phase
motor applications.
The 250 kHz typical bandwidth of the AD8417 provides
instantaneous current monitoring. Additionally, the typical low
offset drift of 0.1 µV/°C means that the measurement error
between the two motor phases is at a minimum over temperature.
The AD8417 rejects PWM input common-mode voltages in the
−2 V to +70 V (with a 5 V supply) range. Monitoring the current
on the motor phase allows sampling of the current at any point
and provides diagnostic information, such as a short to GND
and the battery. Refer to Figure 33 for the typical phase current
measurement setup with the AD8417.
in this type of application. The instability of the ground reference
causes inaccuracies in the measurements that can be made with
a simple ground referenced op amp. The AD8417 measures
current in both directions as the H-bridge switches and the motor
changes direction. The output of the AD8417 is configured in an
external referenced bidirectional mode (see the Bidirectional
Operation section).
CONTROLLER
5V
+IN
MOTOR
VREF 1
VS
OUT
AD8417
SHUNT
–IN
GND VREF 2
NC
2.5V
H-Bridge Motor Control
Another typical application for the AD8417 is to form part of
the control loop in H-bridge motor control. In this case, place
the shunt resistor in the middle of the H-bridge to accurately
measure current in both directions by using the shunt available
at the motor (see Figure 32). Using an amplifier and shunt in
this location is a better solution than a ground referenced op
amp because ground is not typically a stable reference voltage
Figure 32. H-Bridge Motor Control
V+
IU
IV
IW
M
5V
5V
V–
OPTIONAL
DEVICE FOR
OVERCURRENT
PROTECTION AND
FAST (DIRECT)
SHUTDOWN OF
POWER STAGE
INTERFACE
CIRCUIT
AD8417
AD8417
CONTROLLER
BIDIRECTIONAL CURRENT MEASUREMENT
REJECTION OF HIGH PWM COMMON-MODE VOLTAGE (–2V TO +70V)
AMPLIFICATION
HIGH OUTPUT DRIVE
Figure 33. 3-Phase Motor Control
Rev. E | Page 13 of 17
11882-031
AD8214
5V
11882-030
APPLICATIONS INFORMATION
AD8417
Data Sheet
SOLENOID CONTROL
+IN
+
OUTPUT
5
NC
11882-033
4
11882-032
8
NC = NO CONNECT.
GND
In the high rail current sensing configuration, the shunt resistor is
referenced to the battery. High voltage is present at the inputs of
the current sense amplifier. When the shunt is battery referenced,
the AD8417 produces a linear ground referenced analog output.
Additionally, the AD8214 provides an overcurrent detection
signal in as little as 100 ns (see Figure 36). This feature is useful
in high current systems where fast shutdown in overcurrent
conditions is essential.
–IN
3
4
High Rail Current Sensing
NC
2
VREF 2
1
3
Figure 35. High-Side Switch
AD8417
–IN
SWITCH
5
NC = NO CONNECT.
–
SHUNT
2
1
NC
GND
6
INDUCTIVE
LOAD
–IN
CLAMP
DIODE
7
OUT
OUT
VS
+IN
VREF 1
7
8
GND
BATTERY
INDUCTIVE
LOAD
6
AD8417
SHUNT
5V
CLAMP
DIODE
7
8
OUTPUT
–
VREF 2
BATTERY
In this circuit configuration, when the switch is closed, the
common-mode voltage decreases to near the negative rail. When
the switch is open, the voltage reversal across the inductive load
causes the common-mode voltage to be held one diode drop
above the battery by the clamp diode.
+
VREF 1
SWITCH
In the case of a high-side current sense with a low-side switch,
the PWM control switch is ground referenced. Tie an inductive
load (solenoid) to a power supply and place a resistive shunt
between the switch and the load (see Figure 34). An advantage
of placing the shunt on the high side is that the entire current,
including the recirculation current, is measurable because the
shunt remains in the loop when the switch is off. In addition,
diagnostics are enhanced because shorts to ground are detected
with the shunt on the high side.
OUT
High-Side Current Sense with a Low-Side Switch
VS
5V
OVERCURRENT
DETECTION (
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