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INA300: Extending common-mode input range

Bryan McLaughlin
Expert 1110 points

Part Number: INA300

The app note SLLA190: Extending Voltage Range of Current Shunt Monitor was very useful (thanks FAQ page!). 

Could this "Zener drop" technique be used with a high-side current shunt comparator like INA300?

We want to implement a simple current trip on high-side current on a 200V photodiode bias supply. The threshold should be around 10mA, and a sense resistor in the tens-to-hundreds of ohms is acceptable.

  • 0
    TI__Genius 14825 points
    Bryan,
    while it possible to power a device with a zener diode in the way that app note describes, it doesn't work for voltage output devices like the INA300. That one works on the INA138-INA169 family of devices because they are current output.
    It's good that you can accept larger shunt resistors to get the small current of 10mA; using very small resistors would not give you much signal to work with. Have you considered a diff-amp approach? There might also be some merit to voltage dividers on the inputs, but that gets lousy error fast especially with small signals.
  • 0 in reply to Jason Bridgmon
    TI__Genius 14825 points
    Bryan,
    Haven't heard back from you on this in a while, I'm going to close out this thread. If you need further support on this or other TI products, come on back and reply or start a new thread if this one is locked. Happy new year!