AD8206
Single-Supply, 42 V System
Difference Amplifier
AD8206
Ideal for current shunt applications
High common-mode voltage range
−2 V to +65 V operating
−5 V to +68 V survival
Gain = 20
Wide operating temperature range
Die: −40°C to +150°C
8-lead SOIC: −40°C to +125°C
Adjustable offset
Available in SOIC and die form
EXCELLENT AC AND DC PERFORMANCE
15 μV/°C offset drift
30 ppm/°C gain drift
80 dB CMRR dc to 20 kHz
FUNCTIONAL BLOCK DIAGRAM
V+
6
+IN 8
5
OUT
7
VREF1
3
VREF2
–IN 1
AD8206
NC 4
2
NC = NO CONNECT
GND
04953-001
FEATURES
Figure 1.
APPLICATIONS
High-side current sensing in
Motor controls
Transmission controls
Diesel-injection controls
Engine management
Suspension controls
Vehicle dynamic controls
DC-to-dc converters
GENERAL DESCRIPTION
The AD8206 is a single-supply difference amplifier for
amplifying small differential voltages in the presence of large
common-mode voltages. The operating input common-mode
voltage range extends from −2 V to +65 V. The typical singlesupply voltage is 5 V.
The AD8206 is offered in die and packaged form. The operating
temperature range for the die is 25°C higher (up to 150°C) than
the packaged part to enable the user to apply the AD8206 in
high temperature applications.
Excellent DC performance over temperature keeps errors in the
measurement loop to a minimum. Offset drift is typically less
than 15 μV/°C, and gain drift is typically below 30 ppm/°C.
The output offset can be adjusted from 0.08 V to 4.7 V with
a 5 V supply by using the VREF1 and VREF2 pins. With VREF1
attached to the V+ pin, and VREF2 attached to the GND pin,
the output is set at half scale. Attaching both pins to GND
causes the output to be unipolar, starting near ground.
Attaching both pins to V+ causes the output to be unipolar
starting near V+. Other offsets can be obtained by applying
an external voltage to the VREF1 and VREF2 pins.
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
© 2005 Analog Devices, Inc. All rights reserved.
AD8206
TABLE OF CONTENTS
Features .............................................................................................. 1
Unidirectional Operation.............................................................9
Excellent AC and DC Performance................................................ 1
Ground Referenced Output .........................................................9
Applications....................................................................................... 1
V+ Referenced Output .................................................................9
Functional Block Diagram .............................................................. 1
Bidirectional Operation................................................................9
General Description ......................................................................... 1
External ReferenceD Output .................................................... 10
Revision History ............................................................................... 2
Splitting the Supply .................................................................... 10
Specifications..................................................................................... 3
Splitting an External Reference ................................................ 10
Absolute Maximum Ratings............................................................ 4
Applications..................................................................................... 11
ESD Caution.................................................................................. 4
High-Side Current Sense with a Low-Side Switch................. 11
Pin Configuration and Function Descriptions............................. 5
High-Side Current Sense with a High-Side Switch ............... 11
Typical Performance Characteristics ............................................. 6
Outline Dimensions ....................................................................... 12
Theory of Operation ........................................................................ 8
Ordering Guide .......................................................................... 12
Output Offset Adjustment............................................................... 9
REVISION HISTORY
7/05—Revision 0: Initial Version
Rev. 0 | Page 2 of 12
AD8206
SPECIFICATIONS
TA = operating temperature range, VS = 5 V, unless otherwise noted.
Table 1.
Parameter
GAIN
Initial
Accuracy
Accuracy Over Temperature
Gain vs. Temperature
VOLTAGE OFFSET
Offset Voltage (RTI)
Over Temperature (RTI)
Offset Drift
INPUT
Input Impedance
Differential
Common Mode
Input Voltage Range
Common-Mode Rejection
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 Accuracy 3
Accuracy, RTO
Output Offset Adjustment Range
VREF Input Voltage Range
VREF Divider Resistor Values
POWER SUPPLY
Operating Range
Quiescent Current Over Temperature
Power Supply Rejection Ratio
Temperature Range
For Specified Performance
1
2
3
AD8206 SOIC
Min
Typ Max
Conditions
Min
AD8206 DIE
Typ Max
20
VO ≥ 0.1 V dc, 25°C
Specified temperature range
20
±1
±1.2
±1
±1.3
30
25°C
Specified temperature range
Common mode, continuous
Differential 1
25°C, f = dc to 20 kHz 2
Operating temperature range,
f = dc to 20 kHz2
RL = 25 kΩ
±2
±4.5
15
400
200
400
200
−2
76
76
+65
250
86
80
76
76
4.7
+65
250
86
80
0.08
4.7
mV
mV
μV/°C
kΩ
kΩ
V
mV
dB
dB
200
200
V
Ω
100
0.5
100
0.5
kHz
V/μs
20
0.5
20
0.5
μV p-p
μV/√Hz
0.503
±2
0.497
0.503
±2
V/V
mV/V
0.08
0.0
24
4.7
VS
40
0.08
0.0
24
4.7
VS
40
V
V
kΩ
5.5
2
4.5
5.5
2
V
mA
dB
+150
°C
4.5
32
70
−40
32
70
+125
Input voltage range = ±125 mV with half-scale offset.
Source imbalance <2 Ω.
The offset adjustment is ratiometric to the power supply when VREF1 and VREF2 are used as a divider between the supplies.
Rev. 0 | Page 3 of 12
−2
V/V
%
%
ppm/°C
0.497
VO = 0.1 V dc
Operating temperature range
±2.5
±6
15
0.08
Divider to supplies
Voltage applied to VREF1 and VREF2
in parallel
VS = 5 V
30
Unit
−40
AD8206
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Supply Voltage
Continuous Input Voltage
Reverse Supply Voltage
Operating Temperature Range
Storage Temperature Range
Output Short-Circuit Duration
Rating
12.5 V
−5 V to +68 V
0.3 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 and 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
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. 0 | Page 4 of 12
AD8206
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
–IN 1
GND 2
8
AD8206
+IN
VREF1
TOP VIEW
6 V+
(Not to Scale)
5 OUT
NC 4
7
NC = NO CONNECT
04953-003
VREF2 3
Figure 3. Pin Configuration
04953-002
Table 3. Pin Function Descriptions
Figure 2. Metallization Diagram
Pin No.
1
2
3
4
5
6
7
8
Mnemonic
−IN
GND
VREF2
NC
OUT
V+
VREF1
+IN
X
−209
−447
−432
N/A
+444
+444
+456
+207
Y
+486
+34
−480
N/A
−495
−227
+342
+486
Die size is 1245 μm by 1400 μm.
Die thickness is 13 mil.
Minimum passivation opening (minimum bond pad size)
is 92 μm × 92 μm.
Passivation type is 8KA USG (Oxide) + 10KA Oxynitride.
Bond pad metal composition is 98.5% Al, 1% Si, and 0.5% Cu.
Backside potential is V+.
Rev. 0 | Page 5 of 12
AD8206
TYPICAL PERFORMANCE CHARACTERISTICS
40
500
400
35
300
30
25
TYPICAL
IN SOIC
0
–100
TYPICAL
DIE
–200
04953-036
–400
–20
0
20
40
60
80
TEMPERATURE (°C)
15
10
–300
–500
–40
20
100
120
140
5
04953-007
100
GAIN (dB)
VOSI (μV)
200
0
10
100
1k
10k
FREQUENCY (Hz)
100k
1M
Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p)
Figure 4. Typical Offset Drift
120
110
100
90
200mV/DIV
CMR (dB)
80
70
60
50
40
30
10
0
10
100
1k
10k
100k
FREQUENCY (Hz)
1M
1V/DIV
04953-023
04953-004
20
10M
40μs/DIV
Figure 5. CMR vs. Frequency
Figure 8. Rise/Fall Time
12000
250mV/DIV
10000
8000
GAIN ERROR (ppm)
6000
TYPICAL
IN SOIC
4000
2000
0
–2000
TYPICAL
DIE
–4000
2V/DIV
–6000
–12000
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
100
120
04953-025
04953-035
–8000
–10000
140
2μs/DIV
Figure 6. Gain Drift
Figure 9. Differential Overload Recovery (Falling)
Rev. 0 | Page 6 of 12
AD8206
04953-024
2V/DIV
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
04953-030
250mV/DIV
MAXIMUM OUTPUT SINK CURRENT (mA)
0.50
0.05
0
–40
2μs/DIV
Figure 10. Differential Overload Recovery (Rising)
–20
0
20
40
60
80
TEMPERATURE (°C)
100
120
140
Figure 13. Output Sink Current vs. Temperature
04953-022
0.01%/DIV
9
8
7
6
5
4
3
2
1
0
–40
40μs/DIV
04953-031
2V/DIV
MAXIMUM OUTPUT SOURCE CURRENT (mA)
10
Figure 11. Settling Time
–20
0
20
40
60
80
TEMPERATURE (°C)
100
120
140
Figure 14. Output Source Current vs. Temperature
5.0
4.9
50V/DIV
04953-026
50mV/DIV
1μs/DIV
4.7
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
04953-034
OUTPUT VOLTAGE RANGE (V p-p)
4.8
3.6
3.5
0
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT SOURCE CURRENT (mA)
3.5
Figure 15. Output Voltage Range vs. Output Source Current
Figure 12. Common-Mode Response
Rev. 0 | Page 7 of 12
4.0
AD8206
THEORY OF OPERATION
The AD8206 is a single-supply difference amplifier that uses
a unique architecture to accurately amplify small differential
current shunt voltages in the presence of rapidly changing
common-mode voltage. It is offered in both packaged and
die form.
In typical applications, the AD8206 is used to measure current
by amplifying the voltage across a current shunt placed across
the inputs.
The gain of the AD8206 is 20 V/V, with an accuracy of 1.2%.
This accuracy is guaranteed over the operating temperature
range of −40°C to +125°C. The die temperature range is
−40°C to +150°C with a guaranteed gain accuracy of 1.3%.
The input offset is less than 2 mV referred to the input at 25°C,
and 4.5 mV maximum referred to the input over the full
operating temperature range for the packaged part. The die
input offset is less than 6 mV referred to the input over the die
operating temperature range.
The AD8206 operates with a single supply from 4.5 V to
10 V (absolute maximum = 12.5 V). The supply current is
less than 2 mA.
High accuracy trimming of the internal resistors allows the
AD8206 to have a typical common-mode rejection ratio better
than 80 dB from dc to 20 kHz. The minimum common-mode
rejection ratio over the operating temperature is 76 dB for both
the die and packaged part.
The output offset can be adjusted from 0.08 V to 4.7 V
(VS = 5 V) for unidirectional and bidirectional operation.
By attenuating the voltages at Pin 1 and Pin 8, the A1 amplifier
inputs are held within the power supply range, even if Pin 1
and Pin 8 exceed the supply or fall below common (ground). A
reference voltage of 250 mV biases the attenuator above ground.
This allows the amplifier to operate in the presence of negative
common-mode voltages.
The input network also attenuates normal (differential) mode
voltages. A1 amplifies the attenuated signal by 26. The input
and output of this amplifier are differential to maximize the
ac common-mode rejection.
A2 converts the differential voltage from A1 into a single-ended
signal and provides further amplification. The gain of this
second stage is 12.86.
The reference inputs, VREF1 and VREF2, are tied through resistors
to the positive input of A2, 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. The gain is 0.5 V/V when they are used
to divide the supply.
The ratios of Resistors RA, RB, RC, RD, and RF are trimmed to a
high level of precision to allow the common-mode rejection
ratio to exceed 80 dB. This is accomplished by laser trimming
the resistor ratio matching to better than 0.01%.
The total gain of 20 is made up of the input attenuation of
1/16.7 multiplied by the first stage gain of 26 and the second
stage gain of 12.86.
The output stage is a Class A with a PNP pull-up transistor and
a 300 μA current sink pull-down.
–IN
RA
The set of input attenuators preceding A1 consist of RA, RB, and
RC, which reduce the common-mode voltage to match the input
voltage range of A1. The two attenuators form a balanced bridge
network. When the bridge is balanced, the differential voltage
created by a common-mode voltage is 0 V at the inputs of A1.
The input attenuation ratio is 1/16.7. The combined series
resistance of RA, RB, and RC is approximately 200 kΩ ± 20%.
+IN
RA
A1
RB
RB
RC
RC
250mV
RF
RF
RD
RD
A2
AD8206
RE
RF
VOUT
VREF1
RREF
RREF
GND
VREF2
Figure 16. Simplified Schematic
Rev. 0 | Page 8 of 12
04953-013
The AD8206 consists of two amplifiers (A1 and A2), a
resistor network, a small voltage reference, and a bias
circuit (not shown), see Figure 16.
AD8206
OUTPUT OFFSET ADJUSTMENT
The output of the AD8206 can be adjusted for unidirectional or
bidirectional operation.
UNIDIRECTIONAL OPERATION
Unidirectional operation allows the AD8206 to measure
currents through a resistive shunt in one direction. The basic
modes for unidirectional operation are ground referenced
output mode and V+ referenced output mode.
V+ REFERENCED OUTPUT
This 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 18).
V+
+IN
For unidirectional operation, the output can be set at the
negative rail (near ground) or at the positive rail (near V+)
when the differential input is 0 V. The output moves to the
opposite rail when a correct polarity differential input voltage is
applied. In this case, full scale is approximately 250 mV. 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 needs to be negative to move the output down. If the
output is set at ground, the polarity is positive to move the
output up.
OUT
–IN
VREF1
AD8206
NC
VREF2
04953-015
GND
NC = NO CONNECT
Figure 18. V+ Referenced Output
GROUND REFERENCED OUTPUT
When using the AD8206 in this 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 17).
Table 5. V+= 5 V
VIN (Referred to −IN)
0V
−250 mV
VO
4.7 V
0.08 V
V+
+IN
BIDIRECTIONAL OPERATION
OUT
–IN
Bidirectional operation allows the AD8206 to measure currents
through a resistive shunt in two directions.
VREF1
AD8206
NC
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.
VREF2
04953-014
GND
NC = NO CONNECT
Figure 17. Ground Referenced Output
Table 4. V+ = 5 V
VIN (Referred to −IN)
0V
250 mV
VO
0.08 V
4.7 V
Table 6. V+ = 5 V, VO = 2.5 V with VIN = 0 V
VIN (Referred to −IN)
+100 mV
−100 mV
VO
4.5 V
0.5 V
Adjusting the output is accomplished by applying voltage(s) to
the referenced inputs.
VREF1 and VREF2 are tied to internal resistors that connect to an
internal offset node. There is no operational difference between
the pins.
Rev. 0 | Page 9 of 12
AD8206
EXTERNAL REFERENCED OUTPUT
Tying both pins together and to a reference produces an output
equal to the reference voltage when there is no differential input
(see Figure 19). The output moves down from the reference
voltage when the input is negative, relative to the −IN pin and
up when the input is positive, relative to the −IN pin.
V+
+IN
OUT
–IN
VREF1
AD8206
V+
+IN
OUT
–IN
NC
VREF2
VREF1
AD8206
04953-017
GND
NC = NO CONNECT
2.5V VOLTAGE
REFERENCE
Figure 20. Split Supply
NC
SPLITTING AN EXTERNAL REFERENCE
VREF2
NC = NO CONNECT
04953-016
GND
In this case, an external reference is divided by 2 with an
accuracy of approximately 0.5% by connecting one VREF pin to
ground and the other VREF pin to the reference (see Figure 21).
Figure 19. External Referenced Output
SPLITTING THE SUPPLY
V+
+IN
OUT
–IN
VREF1
AD8206
5V
NC
VREF2
GND
NC = NO CONNECT
Figure 21. Split External Reference
Rev. 0 | Page 10 of 12
VOLTAGE
REFERENCE
04953-018
By tying one reference pin to V+ and the other to the ground
pin, the output is set at half of the supply when there is no
differential input (see Figure 20). The benefit is that no external
reference is required to offset the output for bidirectional
current measurement. This 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 goes to 2.75 V.
AD8206
APPLICATIONS
A typical application for the AD8206 is high-side measurement
of a current through a solenoid for PWM control of the solenoid
opening. Typical applications include hydraulic transmission
control and diesel injection control.
Two typical circuit configurations are used for this type of
application.
When using a high-side switch, the battery voltage is connected
to the load when the switch is closed, causing the commonmode voltage to increase to the battery voltage. In this case,
when the switch is opened, the voltage reversal across the
inductive load causes the common-mode voltage to be held
one diode drop below ground by the clamp diode.
5V
HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE
SWITCH
SWITCH
In this case, the PWM control 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 22).
An advantage of placing the shunt on the high side is that the
entire current, including the recirculation current, can be
measured since 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.
42V
BATTERY
+IN VREF1 +VS
OUT
AD8206
SHUNT
–IN
GND VREF2 NC
CLAMP
DIODE
04953-020
INDUCTIVE
LOAD
NC = NO CONNECT
Figure 23. High-Side Switch
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.
5V
42V
BATTERY
INDUCTIVE
LOAD
+IN VREF1 +VS
OUT
AD8206
SHUNT
–IN
The AD8206 measures current in both directions as the
H-bridge switches and the motor changes direction. The
output of the AD8206 is configured in an external reference
bidirectional mode, see the Output Offset Adjustment section.
GND VREF2 NC
NC = NO CONNECT
04953-019
SWITCH
CONTROLLER
5V
Figure 22. Low-Side Switch
HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE
SWITCH
MOTOR
+IN VREF1 +VS
OUT
AD8206
This configuration minimizes the possibility of unexpected
solenoid activation and excessive corrosion (see Figure 23). In
this case, both the switch and the shunt are on the high side.
When the switch is off, this removes the battery from the load,
which prevents damage from potential shorts to ground, while
still allowing the recirculating current to be measured and
providing for diagnostics. Removing the power supply from the
load for the majority of the time minimizes the corrosive effects
that could be caused by the differential voltage between the load
and ground.
Rev. 0 | Page 11 of 12
SHUNT
–IN
GND VREF2 NC
5V
2.5V
NC = NO CONNECT
Figure 24. Motor Control Application
04953-021
CLAMP
DIODE
Another typical application for the AD8206 is as part of
the control loop in H-bridge motor control. In this case, the
AD8206 is placed in the middle of the H-bridge (see Figure 24)
so that it can accurately measure current in both directions by
using the shunt available at the motor. This is a better solution
than a ground referenced op amp because ground is not typically a stable reference voltage in this type of application. This
instability in the ground reference causes the measurements
that could be made with a simple ground referenced op amp to
be inaccurate.
AD8206
OUTLINE DIMENSIONS
5.00 (0.1968)
4.80 (0.1890)
8
5
4.00 (0.1574)
3.80 (0.1497) 1
4
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
6.20 (0.2440)
5.80 (0.2284)
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
COPLANARITY
SEATING 0.31 (0.0122)
0.10
PLANE
0.50 (0.0196)
× 45°
0.25 (0.0099)
8°
0.25 (0.0098) 0° 1.27 (0.0500)
0.40 (0.0157)
0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012AA
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
Figure 25. 8-Lead Standard Small Outline Package [SOIC]
Narrow Body (R-8)
Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model
AD8206YRZ 1
AD8206YRZ-REEL1
AD8206YRZ-REEL71
AD8206YCSURF
1
Temperature Range
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +150°C
Package Description
8-Lead SOIC
8-Lead SOIC, 13” Tape and Reel
8-Lead SOIC, 7” Tape and Reel
Die Form
Z = Pb-free part.
© 2005 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D04953–0–7/05(0)
Rev. 0 | Page 12 of 12
Package Option
R-8
R-8
R-8
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