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INA282-Q1: How to improle for BCI

Tomoaki Yoshida
Expert 2200 points
Part Number: INA282-Q1
Other Parts Discussed in Thread: INA282

Hi,

Our customer has a issue for Bulk Current Injection test.

They are considering countermeasures.

 

#1

They insert condenser each input pin to GND and differential for input noise.

They are thinking of adding capacitors for improvement of input noise.

Please tell me the upper limit capacitance of both the input to GND and between positive and negative inputs.

#2

Is there a recommended countermeasure for BCI?

I think that it is better if only changing constants like #1 above, but please tell me if there is a recommended countermeasure.

Best regards,

Tomoaki Yoshida

  • 0
    TI__Expert 4915 points
    Hi Tomoaki,

    The INA282 Architecture itself already achieves a very high noise rejection ratio, would you be able to describe what issues you're facing in greater detail? Also, what is the bandwidth requirement for the part?
  • 0 in reply to Carlos Silva85
    Expert 2200 points

    Hi Carlos-san,

    I'm sorry for the late reply.

    Their current circuit configuration is as follows:

     Shunt resistance is 0.1 - 0.2 mΩ

     A capacitor between Vin+ and GND is 0.001uF

     A capacitor between Vin- and GND is 0.001uF

     A capacitor between Vin+ and Vin- is 15pF

     Ref is connected to GND

    In upper condition, BCI test result is not good.

    BCI test is Insert current noise into the shunt resistance line.

    So they are considering changing the capacitor constant.

    The required bandwidth is not clear.

    I think that there are restrictions when changing the capacitor constant, but I want to know the limitation.

    Could you tell me the calculation formulas for the bandwidth if it is limited by the bandwidth?

    Also, if it balances with the internal switched capacitor circuit, please tell us the constants and the magnitude of the error.

    Best regards,

    Tomoaki Yoshida

  • 0 in reply to Tomoaki Yoshida
    TI__Expert 4915 points
    Hi Tomoaki,

    Would you be able to provide waveforms for both input and output signals?
  • 0 in reply to Carlos Silva85
    Expert 2200 points
    Hi Carlos-san,

    Thank you for your reply.
    I'm sorry, i don't have a waveform.
    Because BCI test is noise test, then input and output waveform was not acquired.

    For example, are there any concerns about increasing the capacitors?

    Best regards,
    Tomoaki Yoshida
  • 0 in reply to Tomoaki Yoshida
    TI__Expert 4915 points
    Increasing the input capacitors will have an effect in the input bandwidth. I don't know the frequency and waveform of the input, so I cant say whenever this will be a problem or not. If you're able to provide some aditional information I could advise further