AD8211 Analog Devices, AD8211 Datasheet - Page 10

• Manufacturer Part Number: AD8211
• Description: High Voltage Current Shunt Monitor
• Manufacturer: Analog Devices

Specifications of AD8211

• Filter Option: No
• Common Mode Input (v)min: -2V
• Common Mode Input (v)max: +65V
• Bandwidth G=10 (khz Typ): 500kHz
• Cmrr (db): 120dB
• Vcc-vee: 4.5V to 5.5V

AD8211
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.
I
IN
Q1
R1
R
OUT
A1
R
I
SHUNT
SHUNT
GND
Figure 23. Simplified Schematic
PROPRIETARY
CIRCUITRY
OFFSET
AD8211
R
G = +20
V
V+
OUT
= (I
SHUNT
× R
SHUNT
) × 20
Rev. A | Page 10 of 16
A load current flowing through the external shunt resistor
produces a voltage at the input terminals of the AD8211. The
input terminals are connected to Amplifier A1 by Resistor R
and Resistor R1. The inverting terminal, which has very high
input impedance is held to
because negligible current flows through Resistor R. Amplifier
A1 forces the noninverting input to the same potential. Therefore,
the current that flows through Resistor R1, is equal to
This current (I
output buffer amplifier has a gain of 20 V/V and offers excellent
accuracy as the internal gain setting resistors are precision trimmed
to within 0.01% matching. The resulting output voltage is equal to
(V
I
V
IN
OUT
CM
= (I
) − (I
= (I
SHUNT
SHUNT
SHUNT
IN
) is converted back to a voltage via R
× R
× R
× R
SHUNT
SHUNT
SHUNT
)/R1
) × 20
)
OUT
. The