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INA333: current sensing by using INA333 for battery operated device.

Srinivas Beera
Prodigy 220 points
Part Number: INA333

Dear respected, 

This is regarding INA333 in-Amp for using current  measuement for battery operated device. Two connections from battery positive terminal connected VIN+ and VIN- of  INA333 with 0.1Ohm resistor. See attached

image for reference. When I am not shorting System GND to INA GND , there is no change in output from INA> 

When I am connecting System GND and INA GND , I can able to detect current sense. But ideally it has to work without connecting system GND and INA GNDs right????? as we are processing differential inputs 

  

  • 0
    TI__Expert 6250 points
    Hi Srinivas,

    This is likely being caused by an input common mode violation. The input common mode must be between V- +.1 and V+ -.1 volts for the device to function at unity gain. Depending on the configured gain and desired output voltage, the common mode input may be further constrained, as shown in Figures 20-23 in the INA333 datasheet.

    With no connection between the system ground and INA ground, the common mode voltage of the inputs may float unpredictably. Tying the two grounds together fixes this common mode voltage to the battery voltage.