High Voltage,
Precision Difference Amplifier
AD8209A
Data Sheet
FUNCTIONAL BLOCK DIAGRAM
±8000 V HBM ESD for shunt-based applications
AEC-Q100 qualified
EMI filters included
High common-mode voltage range
−2 V to +50 V operating
−20 V to +70 V survival
Buffered output voltage
Gain = 14 V/V
Low-pass filter (single-pole or two-pole)
Wide operating temperature range: −40°C to +125°C
Excellent ac and dc performance
±1 mV typical voltage offset
−5 ppm/°C typical gain drift
80 dB CMRR minimum dc to 10 kHz
Qualified for automotive applications
VS
A1
AD8209A
EMI
FILTER
+IN
EMI
FILTER
–IN
EMI
FILTER
A2
+
+
G=2
–
G=7
–
GND
OUT
14511-001
FEATURES
Figure 1.
APPLICATIONS
High-side current sensing
Motor controls
Solenoid controls
Power management
Low-side current sensing
Diagnostic protection
GENERAL DESCRIPTION
The AD8209A is a single-supply difference amplifier ideal for
amplifying and low-pass filtering small differential voltages in the
presence of a large common-mode voltage. The input commonmode voltage range extends from −2 V to +50 V at a single 5 V
supply. The AD8209A is qualified per AEC-Q100 specifications.
The amplifier offers enhanced input overvoltage and ESD
protection, and includes electromagnetic interference (EMI)
filtering.
Rev. A
Automotive applications demand robust, precision components for
improved system control. The AD8209A provides excellent ac and
dc performance, minimizing errors in the application. Typical
offset and gain drift in the MSOP package are less than 5 µV/°C
and −5 ppm/°C, respectively. The device also delivers a minimum
common-mode rejection ratio (CMRR) of 80 dB from dc to
10 kHz.
The AD8209A features an externally accessible 100 kΩ resistor
at the output of the preamplifier (A1) that can be used for lowpass filtering and for establishing gains other than 14 V/V.
Document Feedback
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
©2016 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
AD8209A
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
High-Side Current Sensing with a Low-Side Switch ............. 11
Applications ....................................................................................... 1
High Rail Current Sensing ........................................................ 11
Functional Block Diagram .............................................................. 1
Low-Side Current Sensing ........................................................ 11
General Description ......................................................................... 1
Gain Adjustment ........................................................................ 12
Revision History ............................................................................... 2
Gain Trim .................................................................................... 13
Specifications..................................................................................... 3
Low-Pass Filtering ...................................................................... 13
Absolute Maximum Ratings ............................................................ 4
ESD Caution .................................................................................. 4
High Line Current Sensing with Low-Pass Filtering and Gain
Adjustment .................................................................................. 14
Pin Configuration and Function Descriptions ............................. 5
Outline Dimensions ....................................................................... 15
Typical Performance Characteristics ............................................. 6
Ordering Guide .......................................................................... 15
Theory of Operation ...................................................................... 10
Automotive Products ................................................................. 15
Applications Information .............................................................. 11
REVISION HISTORY
11/2016—Rev. 0 to Rev. A
Change to Figure 27 ....................................................................... 11
7/2016—Revision 0: Initial Version
Rev. A | Page 2 of 15
Data Sheet
AD8209A
SPECIFICATIONS
Operating temperature (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
SYSTEM GAIN
Initial
Error vs. Temperature
Gain Drift
VOLTAGE OFFSET
Initial Input Offset (Referred to
Input (RTI))
Input Offset (RTI) over
Temperature
Voltage Offset vs. Temperature
INPUT
Input Impedance
Differential
Common Mode
VCM (Continuous)
CMRR 1
PREAMPLIFIER (A1)
Gain
Gain Error
Output Voltage Range
Output Resistance
OUTPUT BUFFER (A2)
Gain
Gain Error
Output Voltage Range 3, 4
Output Voltage Range 5
Input Bias Current
Output Resistance
DYNAMIC RESPONSE
System Bandwidth
Slew Rate
NOISE
0.1 Hz to 10 Hz
Spectral Density, 1 kHz (RTI)
POWER SUPPLY
Operating Range
Quiescent Current
Quiescent Current vs. Temperature
Power Supply Rejection Ratio
(PSRR)
TEMPERATURE RANGE
Test Conditions/Comments
Min
Typ
Max
Unit
V/V
%
ppm/°C
14
0.075 V ≤ VOUT ≤ (VS − 0.1 V), dc, TOPR
TOPR
−5
±0.15
±15
Input common-mode voltage (VCM) = 0.15 V, at TA
±1
±2
mV
±4
mV
+20
µV/°C
440
220
+50
kΩ
kΩ
V
dB
dB
VCM = 0 V, TOPR
VCM = 0 V, TOPR
−20
VCM = −2 V to +50 V, dc
f = dc to 10 kHz, 2 TOPR
360
180
−2
80
80
400
200
100
7
0.0375 V ≤ VOUT ≤ (VS − 0.1 V), dc, TOPR
+0.3
VS − 0.1
103
V/V
%
V
kΩ
−0.3
0.05
+0.3
VS − 0.1
V/V
%
V
0.05
VS − 0.1
50
−0.3
0.025
97
100
2
0.075 V ≤ VOUT ≤ (VS − 0.1 V), dc, TOPR
RL = 25 kΩ, differential input = 0 V, TOPR; Pin 3 (A1 output)
driving Pin 4 (A2 input)
Pin 4 (A2 input) driven with an external source
TOPR
RL = 1 kΩ, frequency = dc
VIN = 0.01 V p-p, VOUT = 0.14 V p-p
VIN = 0.28 V, VOUT = 4 V step
2
V
nA
Ω
100
1
kHz
V/µs
20
500
µV p-p
nV/√Hz
4.5
Typical at TA
VOUT = 0.1 V dc, VS = 5 V, TOPR
VS = 4.5 V to 5.5 V, TOPR
70
For specified performance at TOPR
−40
5.5
1.6
2.7
80
+125
V
mA
mA
dB
°C
Source imbalance < 2 Ω.
The AD8209A preamplifier exceeds 80 dB CMRR at 10 kHz. However, because the output is available only via the 100 kΩ resistor, even a small amount of pin to pin
capacitance between the ±IN pins and the A1 and A2 pins can couple an input common-mode signal larger than the greatly attenuated preamplifier output. The
effect of pin to pin coupling can be neglected in all applications by using a filter capacitor from Pin 3 to GND.
3
The output voltage range of the AD8209A varies depending on the load resistance and temperature. For additional information on this specification, refer to Figure 12
and Figure 13.
4
The output voltage range of A2 assumes that Pin 3 (A1 output) and Pin 4 (A2 input) are shorted together. A 25 kΩ load resistor is used for testing.
5
The output voltage range of A2 assumes Pin 4 (A2 input) is driven with an external voltage source. A 25 kΩ load resistor is used for testing.
1
2
Rev. A | Page 3 of 15
AD8209A
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Supply Voltage
Continuous Input Voltage (Common Mode)
Differential Input Voltage
Reversed Supply Voltage Protection
ESD Human Body Model for Shunt-Based
Applications1
Operating Temperature Range
Storage Temperature Range
Output Short-Circuit Duration
Lead Temperature Range (Soldering 10 sec)
1
Rating
9V
−20 V to +70 V
±16 V
0.3 V
±8000 V
−40°C to +125°C
−65°C to +150°C
Indefinite
300°C
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
Shunt-based applications have a low impedance shunt resistor between +IN
and −IN. See Figure 24 for an example of a shunt-based application.
Rev. A | Page 4 of 15
Data Sheet
AD8209A
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
–IN
+IN
VS
GND
GND
A1 3
TOP VIEW
(Not to Scale)
A2 4
8
+IN
7
VS
6
DNC
5
OUT
DNC = DO NOT CONNECT
A1
A2
OUT
14511-003
AD8209A
14511-002
–IN 1
GND 2
Figure 2. Pin Configuration
Figure 3. Metallization Photograph
Table 3. Pin Function Descriptions1
Pin No.
1
N/A
2
2
3
4
5
N/A
N/A
6
Mnemonic
−IN
OPEN
GND
GND
A1
A2
OUT
OPEN
OPEN
DNC
Coordinates
X
Y
−305
+375
−305
+282
−309
+149
−326
−7
−321
−185
−321
−375
+321
−345
+322
−162
+327
−54
Not applicable Not applicable
Size (μm)
70 × 70
70 × 70
70 × 142
70 × 70
70 × 142
70 × 70
70 × 142
70 × 70
70 × 70
Not applicable
7
N/A
8
VS
OPEN
+IN
+309
+305
+305
70 × 70
70 × 70
70 × 70
1
+185
+375
+282
N/A means not applicable.
Rev. A | Page 5 of 15
Description
Inverting Input.
Bond pads are not connected to any external pins.
Ground.
Ground.
Preamplifier (A1) Output.
Buffer (A2) Input.
Buffer (A2) Output.
No Connect.
Bond pads are not connected to any external pins.
Do Not Connect. Do not connect to this pin; Pin 6
does not connect to any bond pads.
Supply.
Bond pads are not connected to any external pins.
Noninverting Input.
AD8209A
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
TOPR = −40°C to +125°C, TA = 25°C, VS = 5 V, RL = 25 kΩ (RL is the output load resistor), unless otherwise noted.
1000
0.70
0.55
750
0.40
500
GAIN ERROR (ppm)
VOSI (mV)
0.25
0.10
–0.05
–0.20
–0.35
250
0
–250
–500
–0.50
–20
0
20
40
60
80
100
120
140
TEMPERATURE (°C)
–1000
–40
14511-004
–0.80
–40
0
–20
20
40
60
80
120
100
140
TEMPERATURE (°C)
Figure 4. Offset (VOSI) vs. Temperature
14511-007
–750
–0.65
Figure 7. Gain Error vs. Temperature
30
1.0
TOTAL INPUT BIAS CURRENT (mA)
25
20
15
GAIN (dB)
10
5
0
–5
–10
0.8
0.6
0.4
0.2
0
–0.2
10000
100000
–0.4
–24
14511-005
–20
1000
1000000
FREQUENCY (Hz)
12
24
36
48
60
72
Figure 8. Total Input Bias Current vs. Input Common-Mode Voltage,
+IN and −IN Pins Connected (Shorted)
140
–60
130
–55
A2 INPUT BIAS CURRENT (nA)
120
110
100
90
80
70
60
50
–40°C
+25°C
+125°C
–50
–45
–40
–35
–30
–25
–20
100
1k
10k
FREQUENCY (Hz)
Figure 6. CMRR vs. Frequency
100k
1M
–10
A2 INPUT VOLTAGE (V)
14511-009
–15
40
14511-006
CMRR (dB)
0
INPUT COMMON-MODE (V)
Figure 5. Small Signal Bandwidth
30
10
–12
14511-008
–15
Figure 9. A2 Input Bias Current vs. A2 Input Voltage and Temperature
Rev. A | Page 6 of 15
Data Sheet
AD8209A
2.0
OUTPUT VOLTAGE RANGE (V)
MAXIMUM OUTPUT SINK CURRENT (mA)
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
14511-010
0
TEMPERATURE (°C)
0
1
2
3
4
5
6
7
8
9
10
11
12
OUTPUT SINK CURRENT (mA)
Figure 13. A2 Output Voltage Range from GND vs. Output Sink Current
Figure 10. Maximum Output Sink Current vs. Temperature
8.0
INPUT
100mV/DIV
7.0
OUTPUT
6.0
500mV/DIV
–20
0
20
40
60
80
100
120
140
TEMPERATURE (°C)
14511-014
5.0
TIME (2μs/DIV)
14511-011
MAXIMUM OUTPUT SOURCE CURRENT (mA)
9.0
4.0
–40
Figure 14. Rise Time
Figure 11. Maximum Output Source Current vs. Temperature
5.0
100mV/DIV
4.0
INPUT
3.5
3.0
500mV/DIV
2.5
2.0
OUTPUT
0
1
2
3
4
5
6
7
8
OUTPUT SOURCE CURRENT (mA)
TIME (2μs/DIV)
Figure 15. Fall Time
Figure 12. A2 Output Voltage Range vs. Output Source Current
Rev. A | Page 7 of 15
14511-015
1.5
14511-012
OUTPUT VOLTAGE RANGE (V)
4.5
1.0
14511-013
0.2
AD8209A
Data Sheet
200mV/DIV
2V/DIV
INPUT
2V/DIV
0.01%/DIV
TIME (2μs/DIV)
14511-018
14511-016
OUTPUT
TIME (20μs/DIV)
Figure 18. Settling Time, Rising
Figure 16. Differential Overload Recovery, Rising
200mV/DIV
2V/DIV
INPUT
2V/DIV
0.01%/DIV
TIME (20μs/DIV)
Figure 19. Settling Time, Falling
Figure 17. Differential Overload Recovery, Falling
Rev. A | Page 8 of 15
14511-019
TIME (2μs/DIV)
14511-017
OUTPUT
Data Sheet
AD8209A
–3
–2
–1
0
1
2
3
4
VOS (mV)
–20
–5
0
5
10
OFFSET DRIFT (µV/°C)
15
20
14511-021
–10
–5
0
5
10
Figure 22. Gain Drift Distribution
COUNT
–15
–10
GAIN DRIFT (ppm /°C)
Figure 20. Offset Distribution
–20
–15
Figure 21. Offset Drift Distribution
Rev. A | Page 9 of 15
15
20
14511-022
–4
14511-020
COUNT
COUNT
+125°C
+25°C
–40°C
AD8209A
Data Sheet
THEORY OF OPERATION
The AD8209A is a single-supply difference amplifier typically used
to amplify a small differential voltage in the presence of rapidly
changing, high common-mode voltages.
The AD8209A consists of two amplifiers (A1 and A2), a resistor
network, a small voltage reference, and a bias circuit (not shown);
see Figure 23.
The set of input attenuators preceding A1 consist of RA, RB, and
RC, which feature a combined series resistance of approximately
400 kΩ ± 20%. The purpose of these resistors is to attenuate the
input voltage to match the input voltage range of A1. This balanced
resistor network attenuates the common-mode signal by a ratio
of 1/14. The A1 amplifier inputs are held within the power supply
range, even as Pin 1 and Pin 8 exceed the supply or fall below the
common (ground). A reference voltage of 350 mV biases the
attenuator above ground, allowing Amplifier A1 to operate in
the presence of negative common-mode voltages.
The input resistor network also attenuates normal (differential)
mode voltages. Therefore, A1 features a gain of 97 V/V to provide
a total system gain, from ±IN to the output of A1, equal to 7 V/V,
as shown in the following equation:
A low-pass filter can be easily implemented by connecting A1 to
A2 and placing a capacitor to ground (see Figure 32).
The value of RF1 and RF2 is 10 kΩ, providing a gain of 2 V/V for
Amplifier A2. When connecting Pin A1 and Pin A2 together, the
AD8209A provides a total system gain equal to
Total Gain of (A1 + A2) (V/V) = 7 (V/V) × 2 (V/V) = 14 V/V
at the output of A2 (the OUT pin).
The ratios of RA, RB, RC, and RF are trimmed to a high level of
precision, allowing a typical CMRR value that exceeds 80 dB. This
performance is accomplished by laser trimming the resistor ratio
matching to better than 0.01%.
–IN
RA
+IN
VS
RA
–
RF
RB
RG
RC
RC
A2
RFILTER
+
+
RB
A1
A1
OUT
A2
–
RF1
RF
RM
RF2
A precision trimmed, 100 kΩ resistor is placed in series with the
output of Amplifier A1. The user has access to this resistor via
an external pin (A1).
Rev. A | Page 10 of 15
14511-025
350mV
Gain (A1) = 1/14 (V/V) × 97 (V/V) = 7 V/V
GND
Figure 23. Simplified Schematic
Data Sheet
AD8209A
APPLICATIONS INFORMATION
HIGH-SIDE CURRENT SENSING
WITH A LOW-SIDE SWITCH
HIGH RAIL CURRENT SENSING
In load control configurations for high-side current sensing with a
low-side switch, the pulse-width modulation (PWM) controlled
switch is ground referenced. An inductive load (solenoid) connects
to a power supply/battery. A resistive shunt is placed between the
switch and the load (see Figure 24). An advantage of placing the
shunt on the high side is that the entire current, including the
recirculation current, is monitored because the shunt remains
in the loop when the switch is off. In addition, shorts to ground can
be detected with the shunt on the high side, enhancing the
diagnostics of the control loop. 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.
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 AD8209A produces a linear ground-referenced analog output.
Additionally, the AD8214 can be used to provide an overcurrent
detection signal in as little as 100 ns (see Figure 26). This feature is
useful in high current systems where fast shutdown in overcurrent
conditions is essential.
OVERCURRENT
DETECTION (