Datenblatt-pdf.com


AD8479 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD8479
Beschreibung Very High Common-Mode Voltage Precision Difference Amplifier
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 16 Seiten
AD8479 Datasheet, Funktion
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






AD8479 Datasheet, Funktion
AD8479
TYPICAL PERFORMANCE CHARACTERISTICS
VS = ±15 V, TA = 25°C, unless otherwise noted.
60
N = 393
MEAN = –33.5249
SD = 30.5258
50
40
30
20
10
0
–150
–100
–50
0
50 100
CMRR (µV/V)
Figure 4. CMRR Distribution
70 N = 395
MEAN = –29.0415
SD = 57.0658
60
50
40
30
20
10
0
–300
–200
–100 0 100
GAIN ERROR (µV/V)
200
Figure 5. Gain Error Distribution
300
70
N = 377
MEAN = 344.277
60 SD = 1086.57
50
40
30
20
10
0
–4000
–2000 0 2000
OFFSET VOLTAGE (µV)
Figure 6. Offset Voltage Distribution
4000
Data Sheet
100
90
80
70
60
50
40
1
10 100 1k 10k
FREQUENCY (Hz)
Figure 7. CMRR vs. Frequency
100k
1M
120
100
+PSRR
80
–PSRR
60
40
20
0
0.1 1
10 100 1k 10k 100k 1M
FREQUENCY (Hz)
Figure 8. PSRR vs. Frequency
35
VS = ±15V
30
25
20
15
VS = ±5V
10
5
0
100
1k 10k 100k
FREQUENCY (Hz)
Figure 9. Large Signal Frequency Response
1M
Rev. 0 | Page 6 of 16

6 Page









AD8479 pdf, datenblatt
AD8479
APPLICATIONS INFORMATION
BASIC CONNECTIONS
Figure 34 shows the basic connections for operating the
AD8479 with a dual supply. A supply voltage from ±2.5 V to
±18 V is applied across Pin 7 and Pin 4. Both supplies should be
decoupled close to the pins using 0.1 μF capacitors. Electrolytic
capacitors of 10 μF, also located close to the supply pins, may be
required if low frequency noise is present on the power supply.
Although multiple amplifiers can be decoupled by a single set of
10 μF capacitors, each AD8479 should have its own set of 0.1 μF
capacitors so that the decoupling point can be located directly at
the IC power pins.
REF(–)
1
+VS
AD8479
+2.5V TO +18V
8 NC
ISHUNT
(SEE
TEXT)
RSHUNT
–IN
2
+IN
3
7
+VS
0.1µF
(SEE
TEXT)
6 VOUT = ISHUNT × RSHUNT
–VS 4
0.1µF
REF(+)
5
NC = NO CONNECT
–VS
–2.5V TO –18V
Figure 34. Basic Connections
The differential input signal, which typically results from a
load current flowing through a small shunt resistor, is applied to
Pin 2 and Pin 3 with the polarity shown in Figure 34 to obtain a
positive gain. The common-mode voltage on the differential
input signal can range from −600 V to +600 V, and the maximum
differential voltage is ±14.7 V. When configured as shown in
Figure 34, the device operates as a simple gain-of-1, differential-
to-single-ended amplifier; the output voltage is the shunt resistance
times the shunt current. The output is measured with respect to
Pin 1 and Pin 5.
Pin 1 and Pin 5 (REF(−) and (REF(+)) should be grounded for a
gain of unity and should be connected to the same low impedance
ground plane. Failure to do this results in degraded common-mode
rejection. Pin 8 is a no connect pin and should be left open.
SINGLE-SUPPLY OPERATION
Figure 35 shows the connections for operating the AD8479 with
a single supply. Because the output can swing to within only about
0.3 V of either rail, an offset must be applied to the output. This
offset can be applied by connecting REF(+) and REF(−) to a low
impedance reference voltage that is capable of sinking current
(some ADCs provide this voltage as an output). Therefore, for a
single supply of 10 V, VREF can be set to 5 V for a bipolar input
signal, allowing the output to swing ±9.4 V around the central
5 V reference voltage. For unipolar input signals, VREF can be set
to approximately 1 V, allowing the output to swing from 1 V (for
a 0 V input) to within 0.3 V of the positive rail.
Data Sheet
ISHUNT
REF(–)
1
AD8479
+VS
8 NC
RSHUNT
–IN
2
+IN
VX
3
VY
–VS 4
7
+VS
6
0.1µF
REF(+)
5 OUTPUT = VOUT – VREF
NC = NO CONNECT
VREF
Figure 35. Operation with a Single Supply
When the AD8479 is operated with a single supply and a
reference voltage is applied to REF(+) and REF(−), the input
common-mode voltage range of the AD8479 is reduced. The
reduced input common-mode range depends on the voltage at
the inverting and noninverting inputs of the internal op amp,
labeled VX and VY in Figure 35. These nodes can swing to within
1 V of either rail. Therefore, for a single supply voltage of 10 V,
VX and VY can have a value from 1 V to 9 V. If VREF is set to 5 V,
the allowable common-mode voltage range is +245 V to −235 V.
The common-mode voltage range can be calculated as follows:
VCM(±) = 60 × (VX or VY(±)) − (59 × VREF)
SYSTEM-LEVEL DECOUPLING AND GROUNDING
The use of ground planes is recommended to minimize the
impedance of ground returns and, therefore, the size of dc errors.
Figure 36 shows how to use grounding in a mixed-signal environ-
ment, that is, with digital and analog signals present. To isolate
low level analog signals from a noisy digital environment, many
data acquisition components have separate analog and digital
ground returns. All ground pins from mixed-signal components,
such as ADCs, should return through a low impedance analog
ground plane. Digital ground lines of mixed-signal converters
should also be connected to the analog ground plane.
ANALOG POWER
SUPPLY
–5V +5V GND
DIGITAL
POWER SUPPLY
GND +5V
0.1µF
0.1µF 0.1µF
0.1µF
47
–VS +VS
+IN 3
AD8479 OUTPUT 6
–IN 2
REF(–) REF(+)
15
VDD AGND DGND
12
GND VDD
VIN1
ADC
MICROPROCESSOR
VIN2
Figure 36. Optimal Grounding Practice for a Dual Supply Environment
with Separate Analog and Digital Supplies
Rev. 0 | Page 12 of 16

12 Page





SeitenGesamt 16 Seiten
PDF Download[ AD8479 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
AD847High Speed/ Low Power Monolithic Op AmpAnalog Devices
Analog Devices
AD8475Fully Differential Funnel AmplifierAnalog Devices
Analog Devices
AD8476Fully Differential Amplifier and ADC DriverAnalog Devices
Analog Devices
AD8479Very High Common-Mode Voltage Precision Difference AmplifierAnalog Devices
Analog Devices

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche