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INA219: Filter and Protection

Part Number: INA219

Hello:

I have an application using the INA219A to read the current of a motor. I read on section "8.4.1 Filtering and Input Considerations" that is was recommended to protect the inputs of the INA219 with TVS diodes, but I am unsure of the best place they should be. I also wanted to ask for the best way to protect the INA219. I built the following circuit but it seems I am getting a voltage between the INA219 pins of 39mV with no load (less than 2uV on the Rsense resistor). I believe I put the TVS diodes on a wrong position, which is causing this offset.

My application does need all the protection we can get, so I would really appreciate if you could recommend the best practice for it.

The INA219A will measure the current going into an HBRIDGE. Nothing else is connected to the H bridge motor voltage (VMOTOR_IN).

Thanks!

  • Hi Eduardo,

    The position of the TVS seems correct. You can refer to the following TI Design for reference.
    www.ti.com/.../tidu473.pdf

    Have you measure the vsense without the TVS? What is that number?

    Regards
  • Hello Mayrim:

    Thank you for your response. I removed the TVS diode and measured the voltage and it was still the same!

    I removed the capacitor and the system seems to have shorted when I re-applied power. I do rework on a anti-static environment, and I really cannot explain what could have happened when removing the capacitor as it was a simple job.

    However the issue remains on other boards. This 39mV offset is still there without the TVS! I can send you the gerber files of the board if you would like me to, but I think the traces where made as short as possible and routed with similar lengths. I must send you the gerbers to an e-mail address; I cant put them on the forum!

    Thanks,

    -Eduardo Garcia
  • Hi Eduardo,

    You are saying that you measure across the shunt resistor and you see 2uV and then you measure in the INA219 input pins and you see 39mV (with and without the TVS)? If so, I suspect you might be having layout issues.

    Email me your files to see if I can spot something on the layout. mayrim.verdejo@ti.com
  • Hello:

    Thank you for your message. And sorry for the late reply.

    I measured again and now I am getting 130uV on the shunt and 510uV on the capacitor. I will send you the gerber files for the board.

    Thanks!

  • This issue was supported offline. There were layout problems. Proper layout advice was provided to the customer.

    Regards,