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INA333 not supply and input signal over GND

gregoire.lumeau
Intellectual 330 points
Other Parts Discussed in Thread: INA333

Hey,


I would like to use an INA333 to do measure. But some time I switch off INA supply (to reduce energy consumming) and the input signal could have a positive or negative value (arround +/-700mV).

If I do that, can I deteriorate my INA333 ?

NB : input signal and INA supply haven't the same reference.

Thanks for your help

  • 0
    TI__Genius 12335 points

    Gregoire,

    In the powered-down state you risk forward biasing the ESD diodes on the inputs of the INA333. Imagine a diode from each input to the power supply rails. When powered on, these diodes are reversed biased and do not affect the operation of the part. However, when the device is unpowered, an input signal may forward bias the diode. The current through these diodes should be limited to <10mA to avoid damaging them and typically this is done with a series resistor. Because your signal is 700mV a resistor value in the 10s of ohms should be sufficient to protect the inputs in most cases.       

  • 0 in reply to John Caldwell
    Intellectual 330 points

    John,


    Ground of INA and measured signal aren't connected. So I don't think any current through diodes which are between input and power supply.

    If I understand, important parameter is the current which can through the diode. A tension between V+/GND and V-/GND cann't damaged INA while any current is forward ?