AD AD8215

High Voltage,
Current Shunt Monitor
AD8215
±4000 V HBM ESD
High common-mode voltage range
−2 V to +65 V operating
−3 V to +68 V survival
Buffered output voltage
Wide operating temperature range
8-Lead SOIC_N: −40°C to +125°C
Excellent ac and dc performance
6 μV/°C typical offset drift
−8 ppm/°C typical gain drift
120 dB typical CMRR at dc
FUNCTIONAL BLOCK DIAGRAM
IN+
IN–
V+
A1
PROPRIETARY
OFFSET
CIRCUITRY
OUT
G = +20
AD8215
APPLICATIONS
High-side current sensing
Motor controls
Transmission controls
Engine management
Suspension controls
Vehicle dynamic controls
DC-to-dc converters
GND
07203-001
FEATURES
Figure 1.
GENERAL DESCRIPTION
The AD8215 is a high voltage, precision current shunt monitor. It
features a set gain of 20 V/V, with a maximum ±0.3% gain error
over the entire temperature range. The buffered output voltage
directly interfaces with any typical converter. Excellent commonmode rejection from −2 V to +65 V is independent of the 5 V
supply. The AD8215 performs unidirectional current
measurements across a shunt resistor in a variety of industrial
and automotive applications, such as motor controls, solenoid
controls, or battery management.
Special circuitry 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. The AD8215
has an operating temperature range of −40°C to +125°C and is
offered in a small 8-lead SOIC_N package.
Rev. 0
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
©2008 Analog Devices, Inc. All rights reserved.
AD8215
TABLE OF CONTENTS
Features .............................................................................................. 1
Theory of Operation ...................................................................... 10
Applications....................................................................................... 1
Application Notes ........................................................................... 11
Functional Block Diagram .............................................................. 1
Output Linearity......................................................................... 11
General Description ......................................................................... 1
Applications Information .............................................................. 12
Revision History ............................................................................... 2
High-Side Current Sensing with a Low-Side Switch ............. 12
Specifications..................................................................................... 3
High-Side Current Sensing ....................................................... 12
Absolute Maximum Ratings............................................................ 4
Low-Side Current Sensing ........................................................ 12
ESD Caution.................................................................................. 4
Outline Dimensions ....................................................................... 13
Pin Configuration and Function Descriptions............................. 5
Ordering Guide .......................................................................... 13
Typical Performance Characteristics ............................................. 6
REVISION HISTORY
1/08—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
AD8215
SPECIFICATIONS
TOPR = −40°C to +125°C, TA = 25°C, VS = 5 V, RL = 25 kΩ (RL is the output load resistor), unless otherwise noted.
Table 1.
Parameter
GAIN
Initial
Accuracy
Accuracy Over Temperature
Drift
VOLTAGE OFFSET
Offset Voltage, RTI
Over Temperature, RTI
Drift
INPUT
Input Impedance
Differential
Common Mode
Common-Mode Input Voltage Range
Differential Input Voltage Range
Common-Mode Rejection Ratio
Min
Typ
Max
Unit
Conditions
−8
±0.15
±0.3
−15
V/V
%
%
ppm/°C
VO ≥ 0.1 V dc, TA
TOPR
TOPR
+6
±1
±2.5
+18
mV
mV
μV/°C
TA
TOPR
TOPR
+65
kΩ
MΩ
kΩ
V
mV
dB
dB
Common-mode voltage > 5 V
Common-mode voltage < 5 V
Common-mode continuous
Differential input voltage
TOPR, f = dc to 50 kHz, VCM > 5 V
TOPR, f = dc to 40 kHz, VCM < 5 V
20
0
−15
5
5
3.5
−2
100
80
OUTPUT
Output Voltage Range Low
250
120
90
0.03
TA
TOPR
TA
TOPR
2
V
V
V
V
Ω
450
4.5
kHz
V/μs
TOPR
TA
7
70
μV p-p
nV/√Hz
0.10
Output Voltage Range High
4.95
4.90
Output Impedance
DYNAMIC RESPONSE
Small Signal −3 dB Bandwidth
Slew Rate
NOISE
0.1 Hz to 10 Hz, RTI
Spectral Density, 1 kHz, RTI
POWER SUPPLY
Operating Range
Quiescent Current Over Temperature
Power Supply Rejection Ratio
TEMPERATURE RANGE
For Specified Performance
1
4.5
1.3
5.5
2.2
V
mA
dB
+125
°C
75
−40
VCM > 5 V 1 , TOPR
TOPR
When the input common-mode voltage is less than 5 V, the supply current increases, which can be calculated by IS = −0.275 (VCM) + 2.5.
Rev. 0 | Page 3 of 16
AD8215
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Supply Voltage
Continuous Input Voltage
Continuous Differential Input Voltage
Reverse Supply Voltage
Human Body Model (HBM) ESD Rating
Charged Device Model (CDM) ESD Rating
Operating Temperature Range
Storage Temperature Range
Output Short-Circuit Duration
ESD CAUTION
Rating
12.5 V
−3 V to +68 V
0.5 V
−0.3 V
±4000 V
±1000 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.
Rev. 0 | Page 4 of 16
AD8215
1
8
–IN 1
GND 2
AD8215
NC 3
6
55
07203-002
2
TOP VIEW
NC 4 (Not to Scale)
NC
6
V+
5
OUT
Figure 3. Pin Configuration
Table 3. Pin Function Descriptions
Mnemonic
−IN
GND
NC
OUT
V+
+IN
+IN
7
NC = NO CONNECT
Figure 2. Metallization Diagram
Pin No.
1
2
3, 4, 7
5
6
8
8
X
−228
−273
N/A
+265
+273
+229
Y
+519
−251
N/A
−466
−266
+519
Rev. 0 | Page 5 of 16
Description
Inverting Input.
Ground.
No Connect.
Buffered Output.
Supply.
Noninverting Input.
07203-003
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
AD8215
1.2
1.0
0.8
0.6
0.2
GAIN (dB)
VOSI (mV)
0.4
0
–0.2
–0.4
–0.6
–0.8
–1.2
–40
–20
0
20
40
60
80
100
120
TEMPERATURE (°C)
07203-017
–1.0
100k
1M
10M
FREQUENCY (Hz)
Figure 4. Typical Offset Drift vs. Temperature
Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p)
140
10
9
130
TOTAL OUTPUT ERROR (%)
COMMON-MODE VOLTAGE >5V
120
CMRR (dB)
40
35
30
25
20
15
10
5
0
–5
–10
–15
–20
–25
–30
–35
–40
10k
07203-018
TYPICAL PERFORMANCE CHARACTERISTICS
110
COMMON-MODE VOLTAGE <5V
100
90
80
8
7
6
5
4
3
2
70
1
1k
10k
100k
1M
FREQUENCY (Hz)
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 250
DIFFERENTIAL INPUT VOLTAGE (mV)
Figure 5. Typical CMRR vs. Frequency
Figure 8. Total Output Error vs. Differential Input Voltage
2500
–480
2000
–490
INPUT BIAS CURRENT (µA)
1000
500
0
–500
–1000
–500
–510
–520
–540
–550
–2000
–560
–20
0
20
40
60
80
100
TEMPERATURE (°C)
120
Figure 6. Typical Gain Error vs. Temperature
VIN+
–530
–1500
07203-016
GAIN ERROR (ppm)
1500
–2500
–40
07203-022
100
VIN–
–570
0
25
50
75
100
125
150
175
200
225
250
DIFFERENTIAL INPUT VOLTAGE (mV)
Figure 9. Input Bias Current vs. Differential Input Voltage, VCM = 0 V
Rev. 0 | Page 6 of 16
07203-007
10
07203-024
60
AD8215
120
100
100mV/DIV
INPUT
1
90
IN+
80
1V/DIV
70
OUTPUT
IN–
2
60
07203-012
INPUT BIAS CURRENT (µA)
110
50
0
25
50
75
100
125
150
175
200
225
250
DIFFERENTIAL INPUT VOLTAGE (mV)
TIME (400ns/DIV)
07203-006
40
Figure 13. Fall Time
Figure 10. Input Bias Current vs. Differential Input Voltage, VCM = 5 V
0.8
0.4
100mV/DIV
1
–0.4
OUTPUT
–0.8
–1.2
1V/DIV
2
–1.6
07203-015
INPUT BIAS CURRENT (mA)
INPUT
0
–2.0
–4
–2
0
2
4
6
8
65
INPUT COMMON-MODE VOLTAGE (V)
TIME (400ns/DIV)
07203-004
–2.4
Figure 14. Rise Time
Figure 11. Input Bias Current vs. Input Common-Mode Voltage
4.0
200mV/DIV
INPUT
3.0
1
2.5
2V/DIV
2.0
OUTPUT
1.5
1.0
–4
–2
0
2
4
6
8
INPUT COMMON-MODE VOLTAGE (V)
65
07203-013
2
TIME (1µs/DIV)
07203-005
SUPPLY CURRENT (mA)
3.5
Figure 15. Differential Overload Recovery (Falling)
Figure 12. Supply Current vs. Common-Mode Voltage
Rev. 0 | Page 7 of 16
AD8215
12
200mV/DIV
1
OUTPUT
2V/DIV
07203-014
2
11
10
9
8
7
6
5
–40
TIME (1µs/DIV)
–20
0
20
40
60
80
100
120
07203-010
MAXIMUM OUTPUT SINK CURRENT (mA)
INPUT
140
TEMPERATURE (°C)
Figure 16. Differential Overload Recovery (Rising)
Figure 19. Maximum Output Sink Current vs. Temperature
1
2V/DIV
2
07203-019
0.01%/DIV
9
8
7
6
5
4
–40
TIME (4µs/DIV)
–20
0
20
40
60
80
100
120
07203-011
MAXIMUM OUTPUT SOURCE CURRENT (mA)
10
140
TEMPERATURE (°C)
Figure 17. Settling Time (Falling)
Figure 20. Maximum Output Source Current vs. Temperature
5.0
4.6
OUTPUT VOLTAGE RANGE (V)
2V/DIV
1
0.01%/DIV
07203-020
3.8
3.4
3.0
2.6
2.2
1.8
1.4
1.0
TIME (4µs/DIV)
0
1
2
3
4
5
6
7
8
OUTPUT SOURCE CURRENT (mA)
Figure 18. Settling Time (Rising)
Figure 21. Output Voltage Range vs. Output Source Current
Rev. 0 | Page 8 of 16
9
07203-008
2
4.2
AD8215
2.0
2400
1800
1500
1.2
COUNT
OUTPUT VOLTAGE RANGE (V)
2100
1.6
0.8
1200
900
600
0.4
1
2
3
4
5
6
7
8
9
10
11
12
OUTPUT SINK CURRENT (mA)
0
–16
–14
–6
–4
–2
0
15
20
1600
1400
1200
2500
1000
COUNT
2000
1500
800
600
1000
400
500
200
0
–2
–1
0
VOS (mV)
1
2
0
–20
07203-021
COUNT
–8
Figure 24. Gain Drift Distribution
+125°C
+25°C
–40°C
3000
–10
GAIN DRIFT (ppm/°C)
Figure 22. Output Voltage Range from GND vs. Output Sink Current
3500
–12
07203-023
0
07203-009
0
07203-030
300
–15
–10
–5
0
5
OFFSET DRIFT (µV/°C)
Figure 23. Offset Distribution
Figure 25. Offset Drift
Rev. 0 | Page 9 of 16
10
AD8215
THEORY OF OPERATION
In typical applications, the AD8215 amplifies a small differential
input voltage generated by the load current flowing through a
shunt resistor. The AD8215 rejects high common-mode
voltages (up to 65 V) and provides a ground-referenced,
buffered output that interfaces with an analog-to-digital converter
(ADC). Figure 26 shows a simplified schematic of the AD8215.
ISHUNT
RSHUNT
A load current flowing through the external shunt resistor
produces a voltage at the input terminals of the AD8215. The
input terminals are connected to A1 by R and R1. The inverting
terminal, which has very high input impedance, is held to
(VCM) − (ISHUNT × RSHUNT)
because negligible current flows through R. A1 forces the
noninverting input to the same potential. Therefore, the current
that flows through R1 is equal to
IIN = (ISHUNT × RSHUNT)/R1
IIN
R1
R
This current (IIN) is converted back to a voltage via ROUT. The
output buffer amplifier has a gain of 20 V/V and offers excellent
accuracy as the internal gain setting resistors are precision trimmed
to within 0.01% matching. The resulting output voltage is equal to
V+
A1
PROPRIETARY
OFFSET
CIRCUITRY
OUT =
(ISHUNT × RSHUNT ) × 20
AD8215
GND
07203-025
G = +20
ROUT
OUT = (ISHUNT × RSHUNT) × 20
Figure 26. Simplified Schematic
Rev. 0 | Page 10 of 16
AD8215
APPLICATION NOTES
OUTPUT LINEARITY
In all current sensing applications, and especially in automotive
and industrial environments 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 AD8215 contains
specific circuitry on the input stage, which ensures that even
when the differential input voltage is very small and the
common-mode voltage is also low (below the 5 V supply),
the input-to-output linearity is maintained. Figure 27 shows
the differential input voltage vs. the corresponding output
voltage at different common modes.
Regardless of the common mode, the AD8215 provides a
correct output voltage when the differential input is at least
2 mV, which is due to the voltage range of the output amplifier
that can go as low as 33 mV typical. The specified minimum
output amplifier voltage is 100 mV to provide sufficient guardbands. The ability of the AD8215 to work with very small
differential inputs, regardless of the common-mode voltage,
allows for more dynamic range, accuracy, and flexibility in any
current sensing application.
200
180
140
120
100
80
60
40
IDEAL VOUT (mV)
VOUT (mV) @ VCM = 0V
VOUT (mV) @ VCM = 65V
20
07203-026
OUTPUT VOLTAGE (mV)
160
0
0
1
2
3
4
5
6
7
8
9
10
DIFFERENTIAL INPUT VOLTAGE (mV)
Figure 27. Gain Linearity Due to Differential and Common-Mode Voltage
Rev. 0 | Page 11 of 16
AD8215
APPLICATIONS INFORMATION
HIGH-SIDE CURRENT SENSING WITH A LOW-SIDE
SWITCH
OVERCURRENT
DETECTION (<100ns)
In such load control configurations, the PWM-controlled
switch is ground referenced. An inductive load (solenoid) is tied
to a power supply. A resistive shunt is placed between the switch
and the load (see Figure 28). An advantage of placing the shunt on
the high side is that the entire current, including the recirculation
current, can be measured because the shunt remains in the loop
when the switch is off. In addition, diagnostics can be enhanced
because shorts to ground can be detected with the shunt on the
high side. In this circuit configuration, when the switch is
closed, the common-mode voltage moves down to near the
negative rail. When the switch is opened, 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.
5
6
7
8
OUT
GND
NC
–IN
NC
VREG
+IN
VS
4
3
2
1
AD8214
5V
5
6
7
8
OUT
V+
NC
IN+
AD8215
NC
4
SHUNT
CLAMP
DIODE
NC GND IN–
3
2
5
1
INDUCTIVE
LOAD
BATTERY
5V
BATTERY
SWITCH
7
IN+
NC
6
5
07203-028
8
V+ OUT
AD8215
SHUNT
Figure 29. Battery-Referenced Shunt Resistor
IN– GND NC
NC
2
4
5
1
4
3
LOW-SIDE CURRENT SENSING
SWITCH
07203-027
In systems where low-side current sensing is preferred, the
AD8215 provides an integrated solution with great accuracy.
Ground noise is rejected, CMRR is typically higher than 90 dB,
and output linearity is not compromised, regardless of the input
differential voltage.
Figure 28. Low-Side Switch
HIGH-SIDE CURRENT SENSING
In this configuration, the shunt resistor is referenced to the
battery. High voltage is present at the inputs of the current sense
amplifier. In this mode, the recirculation current is again measured
and shorts to ground can be detected. When the shunt is battery
referenced, the AD8215 produces a linear ground-referenced
analog output. An AD8214 can also be used to provide an overcurrent detection signal in as little as 100 ns (see Figure 29).
This feature is useful in high current systems where fast
shutdown in over-current conditions is essential.
5V
5
6
7
8
OUT
V+
NC
IN+
AD8215
NC
4
INDUCTIVE
LOAD
CLAMP
DIODE
SWITCH
BATTERY
NC GND IN–
3
2
1
5
SHUNT
Figure 30. Ground-Referenced Shunt Resistor
Rev. 0 | Page 12 of 16
07203-029
INDUCTIVE
LOAD
CLAMP
DIODE
AD8215
OUTLINE DIMENSIONS
5.00 (0.1968)
4.80 (0.1890)
1
5
4
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
0.10
SEATING
PLANE
6.20 (0.2441)
5.80 (0.2284)
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
0.31 (0.0122)
0.50 (0.0196)
0.25 (0.0099)
45°
8°
0°
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-012-A A
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
012407-A
8
4.00 (0.1574)
3.80 (0.1497)
Figure 31. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model
AD8215YRZ 1
AD8215YRZ-RL1
AD8215YRZ-R71
1
Temperature Range
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
Package Description
8-Lead SOIC_N
8-Lead SOIC_N, 13” Tape and Reel
8-Lead SOIC_N, 7” Tape and Reel
Z = RoHS Compliant Part.
Rev. 0 | Page 13 of 16
Package Option
R-8
R-8
R-8
AD8215
NOTES
Rev. 0 | Page 14 of 16
AD8215
NOTES
Rev. 0 | Page 15 of 16
AD8215
NOTES
©2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D07203-0-1/08(0)
Rev. 0 | Page 16 of 16