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OPA381: Using input for overload protection

Part Number: OPA381
Other Parts Discussed in Thread: INA381

Hi team,

A customer wants to use the input of OPA381 for overload detection and would like to delay it with an RC filter (switch-on pulses etc). For that they would like to know how much current Vout can drive. They would like to avoid using a voltage follower in between.

Of course you can also filter at the input (page 23 data sheet 8.1.4) - I suppose by diverting the peaks above the shunt with a high pass - but what resistance do you use for the RC element? Do you have a formula for that?

Thanks,

Franz

  • Hi Franz,

    hmm, are you sure that we are talking about the OPA381? Or do you mean the INA381? In the datasheet of the latter section 8.1.4 does exist... :-)

    You want to accomplish an overload protection with the INA381? But you want to make the overload protection immune against "switch on pulses"? You mean "inrush currents"? Yes, this could eventually be done by the help of a suited RC low pass filter.

    Do you want to insert the RC low pass filter between the main output of INA381 and the comparator input of INA381?

    The main output of INA381 is rather strong and can sink or source more than 10mA. See figure 19 of datasheet:

    Kai

  • Hi Kai,

    Yes, your are right! Thank you for clearing up the confusion. I mixed up the name and actually wanted to refer to INA381. All other assumptions you made are correct as well. Your inputs will help!

    Best regards,

    Franz

  • War mir ein Vergnügen :-)

    Viel Glück!

    Kai