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PDF AD8218 Data sheet ( Hoja de datos )
| Número de pieza | AD8218 | |
| Descripción | Bidirectional Current Shunt Monitor | |
| Fabricantes | Analog Devices | |
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Data Sheet
FEATURES
High common-mode voltage range
4 V to 80 V operating
−0.3 V to +85 V survival
Buffered output voltage
Gain = 20 V/V
Wide operating temperature range: −40°C to +125°C
Excellent ac and dc performance
±100 nV/°C typical offset drift
±50 µV typical offset
±5 ppm/°C typical gain drift
110 dB typical CMRR at dc
APPLICATIONS
High-side current sensing
48 V telecom
Power management
Base stations
Bidirectional motor control
Precision high voltage current sources
GENERAL DESCRIPTION
The AD8218 is a high voltage, high resolution current shunt
amplifier. It features a set gain of 20 V/V, with a maximum
±0.35% gain error over the entire temperature range. The
buffered output voltage directly interfaces with any typical
converter. The AD8218 offers excellent input common-mode
rejection from 4 V to 80 V. The AD8218 performs bidirectional
current measurements across a shunt resistor in a variety of
industrial and telecom applications, including motor control,
battery management, and base station power amplifier bias
control.
Zero Drift, Bidirectional
Current Shunt Monitor
AD8218
FUNCTIONAL BLOCK DIAGRAM
VS
AD8218
R4
–IN
+IN
ENB
R1
R2
LDO R3
OUT
REF
Figure 1.
GND
The AD8218 offers breakthrough performance throughout the
−40°C to +125°C temperature range. It features a zero-drift core,
which leads to a typical offset drift of ±100 nV/°C throughout
the operating temperature range and the common-mode voltage
range. Special attention is devoted to output linearity being
maintained throughout the input differential voltage range of
0 mV to ~250 mV. The AD8218 also includes an internal 80 mV
reference that can be enabled for optimal dynamic range in
unidirectional current sense applications. The typical input
offset voltage is ±50 µV.
The AD8218 is offered in an 8-lead MSOP package and an
8-lead LFCSP package.
Rev. B
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 ©2011–2013 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
AD8218
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Maximum Input Voltage ( +IN, −IN to GND)
Differential Input Voltage (+IN to –IN)
Human Body Model (HBM) ESD Rating
Operating Temperature Range (TOPR)
Storage Temperature Range
Output Short-Circuit Duration
Rating
−0.3 V to +85 V
±5 V
±2000 V
−40°C to +125°C
−65°C to +150°C
Indefinite
Data Sheet
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. B | Page 4 of 16
5 Page 
AD8218
THEORY OF OPERATION
AMPLIFIER CORE
In typical applications, the AD8218 amplifies a small differential
input voltage generated by the load current flowing through
a shunt resistor. The AD8218 rejects high common-mode vol-
tages (up to 80 V) and provides a ground-referenced, buffered
output. Figure 28 shows a simplified schematic of the AD8218.
ILOAD
ICHARGE
AD8218
5V CF
VS GND
R4
LOAD
V2
V1
4V
TO
80V
–IN
SHUNT +IN
ENB
R1
R2
LDO R3
OUT
REF
VREF
GND
Figure 28. Simplified Schematic
Data Sheet
The AD8218 is configured as a difference amplifier. The
transfer function is
OUT = ((R4/R1) × (V1 − V2)) + VREF
Resistors R4 and R1 are matched to within 0.01% and have
values of 1.5 MΩ and 75 kΩ, respectively, meaning an input-
to-output total gain of 20 V/V for the AD8218. The difference
between V1 and V2 is the voltage across the shunt resistor, or
VIN. Therefore, the input-to-output transfer function of the
AD8218 is
OUT (V) = (20 × VIN) + VREF
The AD8218 accurately amplifies the input differential signal,
rejecting high voltage common modes ranging from 4 V to 80 V.
The main amplifier uses a novel zero-drift architecture, providing
the end user with breakthrough temperature stability. The
offset drift is typically less than ±100 nV/°C. This performance
leads to optimal accuracy and dynamic range.
OUTPUT CLAMPING
After the input common-mode voltage in the application is
above 5.2 V, the internal LDO output of the AD8218 also
reaches its maximum value of 5.2 V, which is the maximum
output range of the AD8218. Because in typical applications
the output interfaces with a converter, clamping the AD8218
output voltage to 5.2 V ensures that the ADC input is not
damaged due to excessive overvoltage.
Rev. B | Page 10 of 16
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet AD8218.PDF ] | |
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