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ADA4099 Maximum Input voltage without supply

Category: Datasheet/Specs
Product Number: ADA4099

Will the +80V maximum input voltage still apply when the amplifier is not supplied?

Im currently working on a battery protection system where the ADA4099 is used to measure the current of the battery, however there can be cases where the battery is connected and the ADA4099 is not supplied (5V voltage regulator for the supply voltage is not connected to the battery). Is the ADA4099 still capable of 50V input voltage and 50V differential input voltage?

best regards
Peter

  • Hi Peter,

    We are checking on this.
    But first I want to confirm. When you say "not supplied", does it mean that the supply is floating or is it at 0V?

    Thanks and Best Regards,
    Sham

  • I would say that it is partially floating. The OPAMP is supplied from a common 5V rail.

    This 5V rail could be actually floating, but there are other parts on this 5V rail that would draw power. GND connection is pretty much guaranteed all of the time, so those other devices would pull the 5V rail to GND to some degree.

    However it would be possible to add a Diode to the supply pin in which case the supply voltage would be floating.

    The only thing that could be potentially dangerous is, that the amplfier is used to control a mosfet so it should not exceed 20V output when the 5V rail is floating.

  • Hi Peter,

    When the ADA4099 is unpowered, the input will be on a high impedance state. If you input 50V then 50V will be visible in the input.

    As for the output, it will still sink or source current from the supplies only this time, the value of VCC and VEE will be low.

    But if we ensure that SHUTDOWN mode is enabled, the output will appear as high impedance with two steering diodes connected to either supply.

    Best Regards,
    Sham

  • Hi Sham,

    thank you for your research. This helps me a lot Slight smile

    Best Regards,
    Peter