High Voltage, High Precision Current Sensing with Output Level Shifting Using the AD8210 Current Sense Amplifier and the AD8274 Difference Amplifier (CN0116)
Current monitoring is a critical function in a variety of applications such as power management, solenoid control, and motor control. Accurate current sensing and diagnostic protection from shorts to GND are achieved by monitoring current on the high side of the load.
An integrated device such as the AD8210 simplifies high side current monitoring by providing a high voltage interface and bidirectional current monitoring capability across the shunt resistor. The AD8210 offers high common-mode rejection (CMR) and excellent temperature performance, for optimal accuracy in the application. The AD8210 amplifies the current flowing through a shunt resistor to a load and provides a ground referenced output voltage that is proportional to the load current.
In applications where dual supplies are used, the output of the AD8210 can drive a precision, low distortion difference amplifier like the AD8274, as shown in Figure 1. The AD8274 provides additional gain and level shifts the AD8210 output to around a desired output common-mode voltage. This facilitates interfacing to other circuit components that use dual supplies. The precision AD780 provides a 2.5 V reference voltage that enables bidirectional current monitoring by the AD8210 and also provides a reference voltage for the AD8274 level shifting function.
Figure 1. Current Sensing and Level Shifting Around GND Using the AD8210, AD8274, and AD780 (Simplified Schematic: Decoupling and All Connections Not Shown)
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