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PDF AD8418 Data sheet ( Hoja de datos )
| Número de pieza | AD8418 | |
| Descripción | Current Sense Amplifier | |
| Fabricantes | Analog Devices | |
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Data Sheet
Bidirectional, Zero Drift,
Current Sense Amplifier
AD8418
FEATURES
Typical 0.1 µV/°C offset drift
Maximum ±400 µV voltage offset over full temperature range
2.7 V to 5.5 V power supply operating range
Electromagnetic interference (EMI) filters Included
High common-mode input voltage range
−2 V to +70 V operating
−4 V to +85 V survival
Initial gain = 20 V/V
Wide operating temperature range: −40°C to +125°C
Bidirectional operation
Available in 8-lead SOIC and 8-lead MSOP
Common-mode rejection ratio (CMRR): 86 dB, dc to 10 kHz
Qualified for automotive applications
APPLICATIONS
High-side current sensing in
Motor controls
Solenoid controls
Power management
Low-side current sensing
Diagnostic protection
GENERAL DESCRIPTION
The AD8418 is a high voltage, high resolution current shunt
amplifier. It features an initial gain of 20 V/V, with a maximum
±0.15% gain error over the entire temperature range. The
buffered output voltage directly interfaces with any typical
converter. The AD8418 offers excellent input common-mode
rejection from −2 V to +70 V. The AD8418 performs bidirectional
current measurements across a shunt resistor in a variety of
automotive and industrial applications, including motor
control, battery management, and solenoid control.
The AD8418 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 0.1 µV/°C throughout the
operating temperature range and the common-mode voltage
range. The AD8418 is fully qualified for automotive applications
and includes EMI filters and patented circuitry to enable output
accuracy with pulse-width modulation (PWM) type input
common-mode voltages. The typical input offset voltage is
±200 µV. The AD8418 is offered in 8-lead MSOP and SOIC
packages.
Table 1. Related Devices
Part No. Description
AD8205 Current sense amplifier, gain = 50
AD8206 Current sense amplifier, gain = 20
AD8207 High accuracy current sense amplifier, gain = 20
AD8210 High speed current sense amplifier, gain = 20
70V
VCM
0V
50A
ISHUNT
–50A
VCM = –2V TO +70V
FUNCTIONAL BLOCK DIAGRAM
VS = 2.7V TO 5.5V
VS VREF1
ISHUNT
+IN
RSHUNT
–IN
EMI
FILTER
EMI
FILTER
+
G = 20
–
AD8418
OUT
VS
VS/2
GND
VREF2
Figure 1.
0V
VOUT
Rev. 0
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Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor 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
Free Datasheet http://www.datasheet4u.com/
1 page  
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
AD8418
–IN 1
GND 2
VREF2 3
NC 4
AD8418
TOP VIEW
(Not to Scale)
8 +IN
7 VREF1
6 VS
5 OUT
NC = NO CONNECT. DO NOT
CONNECT TO THIS PIN.
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
Mnemonic
1 −IN
2 GND
3 VREF2
4 NC
5 OUT
6 VS
7 VREF1
8 +IN
Description
Negative Input.
Ground.
Reference Input 2.
No Connect. Do not connect to this pin.
Output.
Supply.
Reference Input 1.
Positive Input.
Rev. 0 | Page 5 of 16
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5 Page 
Data Sheet
OUTPUT OFFSET ADJUSTMENT
The output of the AD8418 can be adjusted for unidirectional or
bidirectional operation.
UNIDIRECTIONAL OPERATION
Unidirectional operation allows the AD8418 to measure currents
through a resistive shunt in one direction. The basic modes for
unidirectional operation are ground referenced output mode
and VS referenced output mode.
For unidirectional operation, the output can be set at the negative
rail (near ground) or at the positive rail (near VS) when the
differential input is 0 V. The output moves to the opposite rail
when a correct polarity differential input voltage is applied. 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 must be positive to move
the output up.
Ground Referenced Output
When using the AD8418 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 27).
VS
AD8418
R4
R1
–IN –
+IN +
R2
R3
OUT
VREF1
VREF2
GND
Figure 27. Ground Referenced Output
AD8418
VS 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 28).
VS
AD8418
R4
R1
–IN –
+IN +
R2
R3
OUT
VREF1
VREF2
GND
Figure 28. VS Referenced Output
BIDIRECTIONAL OPERATION
Bidirectional operation allows the AD8418 to measure currents
through a resistive shunt in two directions.
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.
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 11 of 16
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AD8418.PDF ] | |
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