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TPS7A11: Output capicator

Joe DiBartolomeo
Expert 3015 points
Part Number: TPS7A11

All,


Customer question on the output capacitor (capacitance) for the TPS7A11, I see in the datasheet a maximum output capacitor of 22uF placed as close as possible to the output pin. In this case Cout is 4.7uF, so OK here.

At the processor ~ 20 mm away there is a large cap 47uF and smaller  decoupling capacitors. 

How will this affect the TPS7A11 stability.

 

Thanks,

Regards,

Joe

  • 0
    TI__Mastermind 36565 points

    Hi Joe,

    The stability of the linear regulator is based on the impedance of the load.
    The datasheet lists 2.2uF minimum and 22uF maximum with an ESR of less than 250m ohms.

    While the different dielectric's make a difference in the equivalent output impedance of a parallel capacitor network, it is likely that the ESR requirement is being met.
    However the total capacitance is not being met.

    The customer should reduce the combination of the output capacitance to be below 22uF under all circumstances (tolerances) to ensure stability across temperature, tolerance and process variations.

    Thanks,

    - Stephen