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TPS7A7001: TPS7A7001

Pechetti Sunitha
Prodigy 20 points
Part Number: TPS7A7001

In the datasheet of TPS7A7001, why the resistor R2 value has to be chosen between 27kohm and 33kohm. what will happen if choose resistor R2 value beyond this range.

  • 0
    TI__Guru 50150 points

    Hi Pechetti,

    This recommendation is to make sure that the current through R1 and R2 is well in excess of the worst possible leakage into the FB pin. For example for 1V output. Both R1 and R2 would be 30K. The current through R1 and R2 would be ~16 times the worst-case leakage into the FB pin. If Vout were set to 5V, then this would only be ~3 times the leakage into the pin. 

    As the current through R1 and R2 decreases,  the chance of the leakage into the FB pin increases.

    Using smaller values is OK, it justs consumes extra power. 

    I hope this helps.

  • 0 in reply to JCHK
    Prodigy 20 points

    Kindly tell me how to calculate leakage current which is flowing into the FB pin. As u considered  for 1V output , both resistors R1, R2 would be 30K. For that case, total current flowing through the resistors are 1V/60K which is equal to 16uA. but I did not know how to calculate the current flowing into the FB pin. And also I did not understand for 5V output, how leakage current is 3 times of the worst case leakage into the pin.

  • 0 in reply to Pechetti Sunitha
    TI__Guru 50150 points

    Hi Pechetti,

    Sorry, I show have included this in my previous response:

    The FB pin current in the datasheet has a maximum of 1uA. This is covering the full temperature range.

    For 5V Output, then datasheet recommends R1 and R2 with values of 274k and 30.1k, So the total current through the pins would be 16uA. if 1uA of this goes into the feedback pin the impact to accuracy is negligible.

    I hope this helps to clarify.