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TPS62260: Stability

Michael Balourdas
Expert 5135 points
Part Number: TPS62260
Other Parts Discussed in Thread: TPS62821,

Hello,

My customer wants to use this device but has some concerns over stability with different output filters. From the datasheet: 

"The TPS6226x is designed to operate with inductors in the range of 1.5 μH to 4.7 μH and with output capacitors in the range of 4.7 μF to 22 μF. The part is optimized for operation with a 2.2-μH inductor and 10-μF output capacitor. Larger or smaller inductor values can be used to optimize the performance of the device for specific operation conditions. For stable operation, the L and C values of the output filter may not fall below 1-μH effective inductance and 3.5-μF effective capacitance. Selecting larger capacitors is less critical because the corner frequency of the L-C filter moves to lower frequencies with fewer stability problems."

This seems kind of vague, is there really no stability concern for using an inductor/capacitor combination much larger than the minimum? Wouldn't very high output capacitance cause instability in a voltage mode converter? 

This table from the TPS62821 datasheet gives specific verified LC combinations, is there anything like this for TPS62260?

Thanks,

Michael

  • 0
    TI__Mastermind 21760 points

    Hi Michael,

    As you have quoted above, the device is designed for specific L/C combinations.

    "Selecting larger capacitors is less critical because the corner frequency of the L-C filter moves to lower frequencies with fewer stability problems."

    This statement is vague. I agree. As you know this is an old part and it would be challenging to find explanation immediately. Unfortunately, we do not have the L/C combination table for this device. In general, with any L/C filter combination you want to use for any device, I suggest to test loop stability first.

    As we are discussing the same issue internally, I hope you would be fine to close this post and proceed internally through E-mail.

    Regards,

    Febin