AD629BR Analog Devices Inc, AD629BR Datasheet - Page 9

• Manufacturer Part Number: AD629BR
• Description: Instrumentation Amplifier IC
• Manufacturer: Analog Devices Inc

Specifications of AD629BR

• No. Of Amplifiers: 1
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Peak Reflow Compatible (260 C): No
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC
• Rohs Status: RoHS non-compliant
• Design Resources: Measuring -48 V High-Side Current Using AD629, AD8603, AD780, and AD7453 (CN0100)
• Amplifier Type: Differential
• Number Of Circuits: 1
• Slew Rate: 2.1 V/µs
• -3db Bandwidth: 500kHz
• Voltage - Input Offset: 100µV
• Current - Supply: 900µA
• Current - Output / Channel: 25mA
• Voltage - Supply, Single/dual (±): 5 V ~ 36 V, ±2.5 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Output Type: -
• Gain Bandwidth Product: -
• Current - Input Bias: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

THEORY OF OPERATION
The AD629 is a unity gain, differential-to-single-ended
amplifier (diff amp) that can reject extremely high common-
mode signals (in excess of 270 V with 15 V supplies). It consists
of an operational amplifier (op amp) and a resistor network.
To achieve high common-mode voltage range, an internal
resistor divider (Pin 3 or Pin 5) attenuates the noninverting
signal by a factor of 20. Other internal resistors (Pin 1, Pin 2,
and the feedback resistor) restore the gain to provide a differential
gain of unity. The complete transfer function equals
Laser wafer trimming provides resistor matching so that
common-mode signals are rejected while differential input
signals are amplified.
V
OUT
= V (+IN) − V (−IN)
Rev. B | Page 9 of 16
To reduce output drift, the op amp uses super beta transistors
in its input stage. The input offset current and its associated
temperature coefficient contribute no appreciable output
voltage offset or drift, which has the added benefit of reducing
voltage noise because the corner where 1/f noise becomes
dominant is below 5 Hz. To reduce the dependence of gain
accuracy on the op amp, the open-loop voltage gain of the op
amp exceeds 20 million, and the PSRR exceeds 140 dB.
REF(–)
–V
+IN
–IN
Figure 29. Functional Block Diagram
S
1
2
3
4
21.1kΩ
AD629
380kΩ
380kΩ
NC = NO CONNECT
380kΩ
20kΩ
8
7
6
5
NC
+V
OUTPUT
REF(+)
S
AD629