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PDF AD8479 Data sheet ( Hoja de datos )
| Número de pieza | AD8479 | |
| Descripción | Very High Common-Mode Voltage Precision Difference Amplifier | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Data Sheet
Very High Common-Mode Voltage
Precision Difference Amplifier
AD8479
FEATURES
±600 V common-mode voltage range
Rail-to-rail output
Fixed gain of 1
Wide power supply range of ±2.5 V to ±18 V
550 μA typical power supply current
Excellent ac specifications
90 dB minimum CMRR
130 kHz bandwidth
High accuracy dc performance
5 ppm maximum gain nonlinearity
10 µV/°C maximum offset voltage drift
5 ppm/°C maximum gain drift
APPLICATIONS
High voltage current sensing
Battery cell voltage monitors
Power supply current monitors
Motor controls
Isolation
GENERAL DESCRIPTION
The AD8479 is a difference amplifier with a very high input
common-mode voltage range. The AD8479 is a precision device
that allows the user to accurately measure differential signals in
the presence of high common-mode voltages up to ±600 V.
The AD8479 can replace costly isolation amplifiers in applications
that do not require galvanic isolation. The device operates over
a ±600 V common-mode voltage range and has inputs that are
protected from common-mode or differential mode transients
up to ±600 V.
The AD8479 has low offset voltage, low offset voltage drift,
low gain drift, low common-mode rejection drift, and excellent
common-mode rejection ratio (CMRR) over a wide frequency
range.
The AD8479 is available in a space-saving 8-lead SOIC package
and is operational over the −40°C to +125°C temperature range.
FUNCTIONAL BLOCK DIAGRAM
AD8479
REF(–) 1
8 NC
1MΩ
–IN 2
+IN 3
1MΩ
–VS 4
7 +VS
6 OUTPUT
5 REF(+)
NOTES
1. NC = NO CONNECT. DO NOT CONNECT TO THIS PIN.
Figure 1.
800
VS = ±15V
600
400
VS = ±5V
200
0
–200
–400
–600
–800
–20
–15 –10
–5 0
5
VOUT (V)
10 15 20
Figure 2. Input Common-Mode Voltage vs. Output Voltage
Rev. 0
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
©2013 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
REF(–) 1
8 NC
–IN 2 AD8479 7 +VS
+IN 3 TOP VIEW 6 OUTPUT
–VS 4 (Not to Scale) 5 REF(+)
NOTES
1. NC = NO CONNECT. DO NOT CONNECT TO THIS PIN.
Figure 3. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
Mnemonic
Description
1
REF(−)
Negative Reference Voltage Input.
2 −IN
Inverting Input.
3 +IN
Noninverting Input.
4 −VS
Negative Supply Voltage.
5
REF(+)
Positive Reference Voltage Input.
6
OUTPUT
Output.
7 +VS
Positive Supply Voltage.
8 NC
No Connect. Do not connect to this pin.
AD8479
Rev. 0 | Page 5 of 16
5 Page 
Data Sheet
THEORY OF OPERATION
The AD8479 is a unity-gain, differential-to-single-ended
amplifier that can reject extremely high common-mode signals
in excess of 600 V with 15 V supplies. The AD8479 consists of
an operational amplifier (op amp) and a resistor network (see
Figure 33).
AD8479
REF(–) 1
8 NC
1MΩ
–IN 2
+IN 3
1MΩ
–VS 4
7 +VS
6 OUTPUT
5 REF(+)
NOTES
1. NC = NO CONNECT. DO NOT CONNECT TO THIS PIN.
Figure 33. Functional Block Diagram
AD8479
To achieve the high common-mode voltage range, an internal
resistor divider—connected to Pin 3 and Pin 5—attenuates the
noninverting signal by a factor of 60. The internal resistors at
Pin 1 and Pin 2, as well as the feedback resistor, restore the gain
to provide a differential gain of unity.
The complete transfer function is
VOUT = V (+IN) − V (−IN)
Laser wafer-trimming provides resistor matching so that
common-mode signals are rejected and differential input
signals are amplified.
To reduce output voltage drift, the op amp uses super beta tran-
sistors in its input stage. The input offset current and its associated
temperature coefficient contribute no appreciable output voltage
offset or drift, which has the added benefit of reducing voltage
noise because the corner where 1/f noise becomes dominant is
below 5 Hz. To reduce the dependence of gain accuracy on the
op amp, the open-loop voltage gain of the op amp exceeds
20 million V/V, and the PSRR exceeds 90 dB.
Rev. 0 | Page 11 of 16
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AD8479.PDF ] | |
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