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PDF AD8208 Data sheet ( Hoja de datos )
| Número de pieza | AD8208 | |
| Descripción | Precision Difference Amplifier | |
| Fabricantes | Analog Devices | |
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Data Sheet
FEATURES
Qualified for automotive applications
EMI filters included
High common-mode voltage range
−2 V to +45 V operating
−24 V to +80 V survival
Buffered output voltage
Gain = 20 V/V
Low-pass filter (1-pole or 2-pole)
Wide operating temperature range
−40°C to +125°C for WB grade
−40°C to +150°C for WH grade
Excellent ac and dc performance
±1 mV voltage offset
−5 ppm/°C typical gain drift
80 dB CMRR minimum dc to 10 kHz
APPLICATIONS
High-side current sensing
Motor controls
Solenoid controls
Power management
Low-side current sensing
Diagnostic protection
GENERAL DESCRIPTION
The AD8208 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 common-
mode voltage range extends from −2 V to +45 V at a single +5 V
supply. The AD8208 is qualified for automotive applications. The
amplifier offers enhanced input overvoltage and ESD protection,
and includes EMI filtering.
High Voltage,
Precision Difference Amplifier
AD8208
FUNCTIONAL BLOCK DIAGRAM
VS A1 A2
EMI
FILTER
+IN
EMI
FILTER
–IN
EMI
FILTER
+
G = 10
–
AD8208
+
G=2
–
OUT
GND
Figure 1.
Automotive applications demand robust, precision components for
improved system control. The AD8208 provides excellent ac and
dc performance, minimizing errors in the application. Typical
offset and gain drift in both the SOIC and MSOP packages are
less than 5 µV/°C and 10 ppm/°C, respectively. The device also
delivers a minimum CMRR of 80 dB from dc to 10 kHz.
The AD8208 features an externally accessible 100 kΩ resistor at
the output of the preamplifier (A1), which can be used for low-
pass filtering and for establishing gains other than 20.
Rev. C
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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2010–2013 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
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
Operating Temperature Range
WBR and WBRM Grade
WHR and WHRM Grade
Storage Temperature Range
Output Short-Circuit Duration
Lead Temperature Range (Soldering, 10 sec)
Rating
12 V
−24 V to +80 V
±12 V
0.3 V
±4000 V
−40°C to +125°C
−40°C to +150°C
−65°C to +150°C
Indefinite
300°C
AD8208
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. C | Page 5 of 20
5 Page 
Data Sheet
THEORY OF OPERATION
The AD8208 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 AD8208 consists of two amplifiers (A1 and A2), a resistor
network, a small voltage reference, and a bias circuit (not shown);
see Figure 24.
The set of input attenuators preceding A1 consists 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 140 V/V to provide
a total system gain, from ±IN to the output of A1, equal to 10
V/V, as shown in the following equation:
Gain (A1) = 1/14 (V/V) × 140(V/V) = 10 V/V
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). A low-pass filter can be easily implemented
AD8208
by connecting A1 to A2 and placing a capacitor to ground (see
Figure 33).
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
AD8208 provides a total system gain equal to
Total Gain of (A1 + A2) (V/V) = 10 (V/V) × 2 (V/V) = 20 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 +IN VS
A1 A2
RA RA
RB
RF RC
RB
RG
RC
+
A1
–
RFILTER
RF
+
A2
–
RM
OUT
RF1
RF2
350mV
GND
Figure 24. Simplified Schematic
Rev. C | Page 11 of 20
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet AD8208.PDF ] | |
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