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DRV401 frequent power on-off-on

Keiichi Kajino
Expert 2365 points
Other Parts Discussed in Thread: DRV401

Hi, folks

I would like to know what happens on current sensing application which uses DRV401 when DRV401's power will be on-off-on while current flowing.

We suspect the induced current will cause voltage on device pin, especially ISx and ICOMPx pin.

I understand this is not a device question, but I would like to in a application point of view. 

  • 0
    TI__Genius 15410 points

    Hello,
     
    The DRV401 has diodes from the input terminals to the power supply rails. Therefore if there is a voltage on pins ISx while the device is powered off, the current should be limited to less than +/-75mA or the device can be damaged.

    The inputs to the differential amplifier (pin Icompx) is NOT internally protected against over voltage. Therefore, the current into these pins should be limited to less than 5mA and less than +/-10V or the device can be damaged.

    This information can be found on page 2 of the datasheet under the ABSOLUTE MAXIMUM RATINGS section.

    I recommend checking out our TI Precision Lab videos that go over Electrostatic Discharge (ESD) and Electrical Overstress (EOS).

    -Tim Claycomb

  • 0 in reply to Tim Claycomb
    Expert 2365 points

    Tim,

    Thanks you for your reply.

    Because of H bridge's drive ability is up to 250mA, I guess the current which should be compensated will be same value.
    As you mentioned, the limitation of 5mA of Icompx pin, I suspect the DRV401 can not alive if power off with measured current flowing. Am I correct?

    I know about what is EOS and ESD. This is why I wrote as  "application point of view" in advance.

  • 0 in reply to Keiichi Kajino
    TI__Genius 15410 points

    Hello Kajino-san,

    I believe I misspoke in my last post. The current must be limited to 5mA and +/-10V on the IAinx pins to the differential amplifier (not the Icompx pins). I am very sorry for any confusion this has caused.

    When the device is powered off, the H bridge will not output a current out of the Icompx pins. Therefore as long as the input pins to the differential amplifier (pins IAinx) are limited to +/-10V and 5mA, and the input pins, ISx, are limited to +/-75mA, the device will not be damaged.

    -Tim Claycomb

  • 0 in reply to Tim Claycomb
    Expert 2365 points
    Hello Tim.

    I got it. Thank you.
  • 0 in reply to Tim Claycomb
    Expert 2365 points
    Hello, Tim

    I suspect that latch-up when the device is ramping-up.
    Is the DRV401 stable during power ramp-up with the current flowing from/to IS?
  • 0 in reply to Keiichi Kajino
    TI__Genius 15410 points

    Hello Keiichi,

    I am looking into the possibility of latch up when the device is ramping up. I will provide an answer as soon as possible.

    Thank you,

    -Tim Claycomb

  • 0 in reply to Tim Claycomb
    TI__Genius 15410 points

    Hello Kajino-san,

    Thank you for your patience.

    After further consideration of the possibility of latch up, I do not believe the device will latch up. However, I do believe that it is likely that the device will be damaged.

    When the device is powered off, flux will build up in the magnetic sensor because there will be no current flowing through the compensation coil. Then when the device is powered back on, the H bridge will want to remove the flux in the magnetic sensor as fast as possible causing a lot of current to flow out of the compensation pins (Icomp1 and Icomp2) until the flux has been removed from the sensor. Therefore, I do not think the DRV401 is the best device for your application.

    If you would like to give more information about your application, I would be happy to try to recommend another solution.

    Thank you,

    -Tim Claycomb

  • 0 in reply to Tim Claycomb
    Expert 2365 points
    Hello Tim

    Thank you for your reply. I understood.