High Resolution, Zero-Drift
Current Shunt Monitor
AD8217
High common-mode voltage range
4.5 V to 80 V operating
0 V to 85 V survival
Buffered output voltage
Wide operating temperature range: −40°C to +125°C
Excellent ac and dc performance
±100 nV/°C typical offset drift
±100 μV typical offset
±5 ppm/°C typical gain drift
100 dB typical CMRR at dc
FUNCTIONAL BLOCK DIAGRAM
R4
AD8217
–IN
R1
OUT
+IN
R2
R3
LDO
09161-001
FEATURES
GND
Figure 1.
APPLICATIONS
High side current sensing
48 V telecom
Power management
Base stations
Unidirectional motor control
Precision high voltage current sources
GENERAL DESCRIPTION
The AD8217 is a high voltage, high-resolution current shunt
amplifier. It features a set gain of 20 V/V, with a maximum
±0.35% gain error over the entire temperature range. The
buffered output voltage directly interfaces with any typical
converter. The AD8217 offers excellent common-mode rejection
from 4.5 V to 80 V, and includes an internal LDO, which directly
powers the device from the high voltage rail. Therefore, no additional supply is necessary, provided that the input common-mode
range is 4.5 V to 80 V. The AD8217 performs unidirectional
current measurements across a shunt resistor in a variety of
industrial and telecom applications including motor control,
battery management, and base station power amplifier bias
control.
The AD8217 offers breakthrough performance throughout the
−40°C to +125°C temperature range. It features a zero-drift
core, which leads to a typical offset drift of ±100 nV/°C
throughout the operating temperature and common-mode
voltage range. Special attention is devoted to output linearity
being maintained throughout the input differential voltage range
of 0 mV to 250 mV, regardless of the common-mode voltage
present, and the typical input offset voltage is ±100 μV.
The AD8217 is offered in a 8-lead MSOP package and is
specified from −40°C to +125°C.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2010–2011 Analog Devices, Inc. All rights reserved.
AD8217
TABLE OF CONTENTS
Features .............................................................................................. 1
Amplifier Core............................................................................ 10
Applications....................................................................................... 1
Internal LDO............................................................................... 10
Functional Block Diagram .............................................................. 1
Application Notes ........................................................................... 11
General Description ......................................................................... 1
Output Linearity......................................................................... 11
Revision History ............................................................................... 2
Applications Information .............................................................. 12
Specifications..................................................................................... 3
High-Side Current Sensing ....................................................... 12
Absolute Maximum Ratings............................................................ 4
Motor Control Current Sensing ............................................... 12
ESD Caution.................................................................................. 4
Outline Dimensions ....................................................................... 13
Pin Configuration and Function Descriptions............................. 5
Ordering Guide .......................................................................... 13
Typical Performance Characteristics ............................................. 6
Theory of Operation ...................................................................... 10
REVISION HISTORY
3/11—Rev. 0 to Rev. A
Changes to Features.......................................................................... 1
Changes to Figure 18........................................................................ 8
7/10—Revision 0: Initial Version
Rev. A | Page 2 of 16
AD8217
SPECIFICATIONS
TOPR = −40°C to +125°C, TA = 25°C, RL = 25 kΩ, input common-mode voltage (VCM = 4.5 V) (RL is the output load resistor), unless
otherwise noted.
Table 1.
Parameter
GAIN
Initial
Accuracy
Accuracy over Temperature
Gain vs. Temperature
VOLTAGE OFFSET
Offset Voltage (RTI) 1
Over Temperature (RTI)1
Offset Drift
INPUT
Bias Current 2
Common-Mode Input Voltage Range
Differential Input Voltage Range 3
Common-Mode Rejection (CMRR)
OUTPUT
Output Voltage Range Low
Output Voltage Range High
Output Impedance
DYNAMIC RESPONSE
Small Signal −3 dB Bandwidth
Slew Rate
NOISE
0.1 Hz to 10 Hz, (RTI)1
Spectral Density, 1 kHz, (RTI)1
POWER SUPPLY
Operating Range
Quiescent Current Over Temperature
Power Supply Rejection Ratio (PSRR)
TEMPERATURE RANGE
For Specified Performance
Min
Typ
Max
Unit
Test Conditions/Comments
V/V
%
%
ppm/°C
VO ≥ 0.1 V dc, TA
TOPR
TOPR
μV
μV
nV/°C
25°C
TOPR
TOPR
250
100
μA
μA
V
mV
dB
TA
TOPR
Common-mode continuous
Differential input voltage
TOPR
TA 4
TA4
2
V
V
Ω
500
1
kHz
V/μs
2.3
110
μV p-p
nV/√Hz
20
±0.1
±0.35
±5
±250
±300
±100
500
800
80
4.5
90
0.01
5
4.5
90
−40
80
800
V
μA
dB
+125
°C
110
1
Power regulated from common mode
Throughout input common mode
TOPR
RTI = referred to input.
Refer to Figure 8 for further information on the input bias current. This current varies based on the input common-mode voltage. Additionally, the input bias current
flowing to the +IN pin is also the supply current to the internal LDO.
3
The differential input voltage is specified as 250 mV typical because the output is internally clamped to 5 V. This ensures the output voltage does not exceed 5 V and
can interface and not cause damage to any typical converter, regardless of the high voltage present at the inputs of the AD8217 (up to 80 V).
4
See Figure 17 and Figure 18 for further information on the output range of the AD8217 with various loads. The AD8217 output clamps to a maximum voltage of 5.6 V
when the voltage at pin +IN is greater than 5.6 V. When the voltage at +IN is less than 5.6 V, the output reaches a maximum value of (V+IN − 100 mV).
2
Rev. A | Page 3 of 16
AD8217
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Maximum Input Voltage ( +IN, −IN to GND)
Differential Input Voltage (+IN to –IN)
HBM (Human Body Model) ESD Rating
Operating Temperature Range (TOPR)
Storage Temperature Range
Output Short-Circuit Duration
Rating
0 V to 85 V
±1 V
±2000 V
−40°C to +125°C
−65°C to +150°C
Indefinite
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
Rev. A | Page 4 of 16
AD8217
+IN 1
NC 2
AD8217
NC 3
TOP VIEW
(Not to Scale)
GND 4
8
–IN
7
NC
6
NC
5
OUT
NC = NO CONNECT
09161-002
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
Mnemonic
+IN
NC
NC
GND
OUT
NC
NC
−IN
Description
Noninverting Input. Supply pin to the internal LDO.
No Connect. No internal connection to pin.
No Connect. No internal connection to pin.
Ground.
Output.
No Connect. No internal connection to pin.
No Connect. No internal connection to pin.
Inverting Input.
Rev. A | Page 5 of 16
AD8217
TYPICAL PERFORMANCE CHARACTERISTICS
30
40
27
38
24
36
MAGNITUDE (dB)
21
VOSI (µV)
34
32
30
18
15
12
9
28
6
26
0
–20
0
20
40
60
80
100
120
140
TEMPERATURE (°C)
1k
Figure 3. Typical Input Offset vs. Temperature
10k
100k
FREQUENCY (Hz)
1M
09161-006
3
09161-003
24
–40
Figure 6. Typical Small-Signal Bandwidth (VOUT = 200 mV p-p)
10
140
9
130
8
TOTAL OUTPUT ERROR (%)
120
CMRR (dB)
110
100
90
–40°C
+25°C
+125°C
80
70
7
6
5
4
3
2
1
0
–1
–2
–3
60
–5
10k
100k
1M
FREQUENCY (Hz)
0
09161-004
1000
Figure 4. Typical CMRR vs. Frequency
450
700
INPUT BIAS CURRENT (µA)
800
400
350
300
250
200
15
20
25
30
35
DIFFERENTIAL INPUT (mV)
40
45
50
+IN
600
500
400
300
200
100
150
–20
0
20
40
60
TEMPERATURE (°C)
80
100
120
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
INPUT COMMON-MODE VOLTAGE (V)
Figure 5. Typical Gain Error vs. Temperature
Figure 8. Input Bias Current vs. Input Common-Mode Voltage
(Differential Input Voltage = 5 mV)
Rev. A | Page 6 of 16
09161-008
–IN
0
09161-005
GAIN ERROR (ppm)
10
Figure 7. Total Output Error vs. Differential Input Voltage
500
100
–40
5
09161-007
–4
50
100
AD8217
INPUT
100mV/DIV
INPUT
5mV/DIV
OUTPUT
2V/DIV
1µs/DIV
5µs/DIV
Figure 9. Rise Time (Differential Input = 5 mV)
09161-012
100mV/DIV
09161-009
OUTPUT
Figure 12. Fall Time (Differential Input = 200 mV)
INPUT
200mV/DIV
INPUT
OUTPUT
2V/DIV
2V/DIV
5µs/DIV
09161-010
OUTPUT
5µs/DIV
Figure 10. Rise Time (Differential Input = 200 mV)
09161-013
100mV/DIV
Figure 13. Differential Overload Recovery, Rising
INPUT
INPUT
5mV/DIV
200mV/DIV
OUTPUT
OUTPUT
100mV/DIV
5µs/DIV
Figure 11. Fall Time (Differential Input = 5 mV)
Figure 14. Differential Overload Recovery, Falling
Rev. A | Page 7 of 16
09161-014
1µs/DIV
09161-011
2V/DIV
AD8217
250
MAXIMUM OUTPUT SINK CURRENT (mA)
11.5
11.0
10.5
10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
0 10 20 30 40 50 60 70 80 90 100 110 120
TEMPERATURE (°C)
150
100
50
0
09161-015
5.0
–40 –30 –20 –10
200
0
Figure 15. Maximum Output Sink Current vs. Temperature
0.5
1.0
1.5
2.0
2.5
3.0
3.5
OUTPUT SINK CURRENT (mA)
4.0
4.5
5.0
Figure 18. Output Voltage Range From GND vs. Output Sink Current
9.0
8.5
INPUT
8.0
50V/DIV
7.5
7.0
6.5
OUTPUT
6.0
1V/DIV
5.5
5.0
4.5
150
TEMPERATURE (°C)
500ns/DIV
09161-016
140
130
110
120
90
100
80
70
60
50
40
30
20
0
10
–10
–20
–30
–40
4.0
09161-019
MAXIMUM OUTPUT SOURCE CURRENT (mA)
9.5
Figure 19. Common-Mode Step Response, Rising
Figure 16. Maximum Output Source Current vs. Temperature
5.000
4.990
INPUT
4.980
50V/DIV
4.970
OUTPUT
4.960
1V/DIV
4.950
4.940
4.930
4.910
4.900
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
OUTPUT SOURCE CURRENT (mA)
4.5
5.0
Figure 17. Output Voltage Range vs. Output Source Current
1µs/DIV
Figure 20. Common-Mode Step Response (Falling)
Rev. A | Page 8 of 16
09161-020
4.920
09161-017
OUTPUT VOLTAGE SWING FROM RAIL (V)
5.010
0
09161-018
OUTPUT VOLTAGE RANGE FROM GND (mV)
12.0
AD8217
1200
700
1000
600
500
800
COUNT
COUNT
800
600
400
300
400
200
–150
–100
–50
0
50
100
150
100
0
200
VOSI (µV)
600
400
200
09161-022
COUNT
800
0
GAIN DRIFT (ppm/°C)
–0.2
0
0.2
Figure 23. Input Offset Drift Distribution
1000
–5
–0.4
OFFSET DRIFT (µV/°C)
Figure 21. Input Offset Distribution
0
–10
09161-023
0
–200
09161-021
200
5
10
Figure 22. Gain Drift Distribution
Rev. A | Page 9 of 16
0.4
AD8217
THEORY OF OPERATION
AMPLIFIER CORE
In typical applications, the AD8217 amplifies a small differential
input voltage generated by the load current flowing through
a shunt resistor. The AD8217 rejects high common-mode voltages (up to 80 V) and provides a ground-referenced, buffered
output that interfaces with an analog-to-digital converter (ADC).
Figure 24 shows a simplified schematic of the AD8217.
R4
AD8217
ILOAD
–IN
R1
V2
SHUNT +IN
V1
4.5V
TO
80V
OUT
R2
R3
LDO
GND
Figure 24. Simplified Schematic
The AD8217 is configured as a difference amplifier. The
transfer function is
OUT = (R4/R1) × (V1 − V2)
Resistors R4 and R1 are matched to within 0.01% and have
values of 1.5 MΩ and 75 kΩ, respectively, meaning an input
to output total gain of 20 V/V for the AD8217.
09161-024
LOAD
The AD8217 accurately amplifies the input differential signal,
rejecting high voltage common modes ranging from 4.5 V to 80 V.
The main amplifier uses a novel zero-drift architecture, providing
the end user with an extremely stable part over temperature.
The offset drift is typically less than ±100 nV/°C. This performance leads to optimal accuracy and dynamic range.
INTERNAL LDO
The AD8217 includes an internal LDO, which allows the device
to power directly from the common-mode voltage at the inputs.
No additional standalone supply is necessary, provided that the
common-mode voltage at the +IN pin is at least 4.5 V and up to
80 V. Once the common-mode voltage is above 5.6 V, the LDO
output reaches its maximum value, that is 5.6 V. This is also the
maximum output voltage range of the AD8217. Because the
AD8217 output typically interfaces with a converter, the 5.6 V
maximum output range ensures the ADC input is not damaged
due to excessive overvoltage.
The input bias current flowing through Pin +IN powers the
internal LDO and, therefore, doubles as the supply current
for the AD8217. This current varies depending on the input
common-mode voltage. See Figure 8 for additional information.
Rev. A | Page 10 of 16
AD8217
APPLICATION NOTES
OUTPUT LINEARITY
In all current sensing applications where the common-mode
voltage can vary significantly, it is important that the current
sensor maintain the specified output linearity, regardless of
the input differential or common-mode voltage. The AD8217
maintains a very high input-to-output linearity even when the
differential input voltage is very small.
Regardless of the common mode, the AD8217 provides a
correct output voltage when the input differential is at least
1 mV. The ability of the AD8217 to work with very small
differential inputs, regardless of the common-mode voltage,
allows for optimal dynamic range, accuracy, and flexibility in
any current sensing application.
200
180
160
OUTPUT (mV)
140
120
100
80
60
40
0
0
1
2
3
4
5
6
7
DIFFERENTIAL INPUT (mV)
8
9
10
09161-025
20
Figure 25. Gain Linearity at Small Differential Inputs (VCM = 4.5 V to 80 V)
Rev. A | Page 11 of 16
AD8217
APPLICATIONS INFORMATION
HIGH-SIDE CURRENT SENSING
MOTOR CONTROL CURRENT SENSING
In this configuration, the shunt resistor is referenced to the
battery (see Figure 26). High voltage is present at the inputs
of the current sense amplifier. When the shunt is battery
referenced, the AD8217 produces a linear ground-referenced
analog output. The AD8217 includes an internal LDO, which
allows the part to be powered from the high voltage rail, with
no need for an additional standalone supply.
The AD8217 is a practical, accurate solution for high-side
current sensing in motor control applications. In cases where
the shunt resistor is referenced to battery and the current
flowing is unidirectional (as shown in Figure 27), the AD8217
monitors the current with no additional supply pin necessary.
BATTERY
IMOTOR
ILOAD
4.5V
TO
80V
SHUNT
ADC
–IN
+IN
MOTOR
–IN
+IN
AD8217
AD8217
09161-026
GND
GND
09161-027
OUT
OUT
Figure 27. High-Side Current Sensing in Motor Control
Figure 26. Battery-Referenced Shunt Resistor
Rev. A | Page 12 of 16
AD8217
OUTLINE DIMENSIONS
3.20
3.00
2.80
8
3.20
3.00
2.80
1
5.15
4.90
4.65
5
4
PIN 1
IDENTIFIER
0.65 BSC
0.95
0.85
0.75
15° MAX
1.10 MAX
0.40
0.25
6°
0°
0.23
0.09
0.80
0.55
0.40
COMPLIANT TO JEDEC STANDARDS MO-187-AA
100709-B
0.15
0.05
COPLANARITY
0.10
Figure 28. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model 1
AD8217BRMZ
AD8217BRMZ-RL
AD8217BRMZ-R7
1
Temperature Range
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
Package Description
8-Lead Mini Small Outline Package (MSOP)
8-Lead Mini Small Outline Package (MSOP)
8-Lead Mini Small Outline Package (MSOP)
Z = RoHS Compliant Part.
Rev. A | Page 13 of 16
Package Option
RM-8
RM-8
RM-8
Branding
Y2L
Y2L
Y2L
AD8217
NOTES
Rev. A | Page 14 of 16
AD8217
NOTES
Rev. A | Page 15 of 16
AD8217
NOTES
©2010–2011 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D09161-0-3/11(A)
Rev. A | Page 16 of 16