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AD8211WYRJZ-R7

P1-P3P4-P6P7-P9P10-P12P13-P14
Data Sheet AD8211
Rev. C | Page 9 of 13
2.0
0
0
06824-116
OUTPUT SINK CURRENT (mA)
OUTPUT VOLTAGE RANGE FROM GND (V)
12
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
1 2 3 4 5 6 7 8 9
10
11
Figure 22. Output Voltage Range from GND vs. Output Sink Current
AD8211 Data Sheet
Rev. C | Page 10 of 13
THEORY OF OPERATION
In typical applications, the AD8211 amplifies a small differential
input voltage generated by the load current flowing through a
shunt resistor. The AD8211 rejects high common-mode voltages
(up to 65 V) and provides a ground referenced, buffered output
that interfaces with an analog-to-digital converter (ADC).
Figure 23 shows a simplified schematic of the AD8211.
06824-022
V+
V
OUT
= (I
SHUNT
× R
SHUNT
) × 20
G = +20
AD8211
A1
PROPRIETARY
OFFSET
CIRCUITRY
GND
R1
R
OUT
Q1
R
I
SHUNT
I
IN
R
SHUNT
Figure 23. Simplified Schematic
A load current flowing through the external shunt resistor
produces a voltage at the input terminals of the AD8211. The
input terminals connect to Amplifier A1 by Resistor R and
Resistor R1. The inverting terminal, which has very high input
impedance, is held to the following because negligible current
flows through Resistor R:
(V
CM
) − (I
SHUNT
× R
SHUNT
)
Amplifier A1 forces the noninverting input to the same potential.
Therefore, the current that flows through Resistor R1 is equal to
I
IN
= (I
SHUNT
× R
SHUNT
)/R1
This current (I
IN
) is converted back to a voltage via R
OUT
. The
output buffer amplifier has a gain of 20 V/V and offers excellent
accuracy because the internal gain setting resistors are precision
trimmed to within 0.01% matching. The resulting output voltage
is equal to
V
OUT
= (I
SHUNT
× R
SHUNT
) × 20
Data Sheet AD8211
Rev. C | Page 11 of 13
APPLICATION NOTES
OUTPUT LINEARITY
In all current sensing applications, and especially in automotive
and industrial environments where the common-mode voltage
can vary significantly, it is important that the current sensor
maintain the specified output linearity, regardless of the input
differential or common-mode voltage. The AD8211 contains
specific circuitry on the input stage, which ensures that even
when the differential input voltage is very small, and the
common-mode voltage is also low (below the 5 V supply),
the input-to-output linearity is maintained. Figure 24 shows
the input differential voltage vs. the corresponding output
voltage at different common modes.
200
0
0
06824-115
DIFFERENTIAL INPUT VOLTAGE (mV)
OUTPUT VOLTAGE (mV)
10
180
160
140
120
100
80
60
40
20
1
2
3
4
5
6 7
8 9
IDEAL V
OUT
(mV)
V
OUT
(mV) @ V
CM
= 0V
V
OUT
(mV) @ V
CM
= 65V
Figure 24. Gain Linearity Due to Differential and Common-Mode Voltage
Regardless of the common mode voltage, the AD8211 provides
a correct output voltage when the input differential is at least
2 mV, which is due to the voltage range of the output amplifier
that can go as low as 33 mV typical. The specified minimum
output amplifier voltage is 100 mV to provide sufficient guard
bands. The ability of the AD8211 to work with very small
differential inputs, regardless of the common-mode voltage,
allows for additional dynamic range, accuracy, and flexibility in
any current sensing application.
P1-P3P4-P6P7-P9P10-P12P13-P14

AD8211WYRJZ-R7

Mfr. #:
Buy AD8211WYRJZ-R7
Manufacturer:
Analog Devices Inc.
Description:
Current Sense Amplifiers High Voltage Current Shunt Amp
Lifecycle:
New from this manufacturer.
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