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INA302-Q1: Power supply recommendations - series resister between VS and bypass cap -

Part Number: INA302-Q1

Hi team,

It is described as below in INA302-Q1 datasheet page 31, 9 Power Supply Recommendations.

"If the use case requires VCM to be present before
VS with VCM under these same slewing conditions, then a 331-Ω resistor must be added between the VS supply
and the VS pin bypass capacitor."

1. The location is as below red line? (just like adding ESR on bypass cap?)

2. Could you advise the mechanism of how this series resister protect the device when VCM > 36V, 6V/us while VS not supplied?

3. Is there minimum or maximum resistance for this 331ohm?

regards,

  • Hello Tsuji-san,

    I will start looking over your questions, but in the meantime, could you resend that image? For some reason it came through too small to see.

  • Hello Tsuji-san,

    Thank you, that image is much easier to read. Here are my responses to your questions:

    1. No, this is not the correct location. The resistor should go where the vertical orange line is.
    2. It does not protect the device when VCM > 36V, but is needed when VCM is between 20V and 36V, when the other specified conditions are present as well. (ie, high VCM ramp, etc.)
    3. 331Ω is the minimum value that should be used. While higher values can be used, it is not recommended to go too much higher. 

     

  • Could you give me the guide line how do you select the value of the resister?

    Why is it recommended as 331ohm?

    regards,

  • Hello Tsuji-san,

    To better explain, the reason for the resistor is that under those specific conditions (high VCM, very fast slew rate, and VCM present before Vs), then it is possible that the device will latch up.  Adding the 331Ω resistor prevents this latch up condition.  This value was selected through various tests combined with design knowledge. During the tests, 331Ω was the lowest value that they could use to reliably not see the latch up issue.  From this it is implied that lower value resistors may still allow latch up, but going much higher is not advisable, as that could begin to hinder performance.  

  • Hello Tsuji-san,

    Sorry, but it turns out that I had the incorrect answer to question #1 above for the resistor placement. I have edited that comment to put the correct answer there.