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Original question:

TPS65911: TPS65911 for G12 - LDO1 problem

TPS65911: TPS65911 for G12 - LDO1 problem

Kamil Kazelle
Prodigy 140 points
Part Number: TPS65911
Other Parts Discussed in Thread: 66AK2G12

Hello,

I wanted to ask if there are some new findings about LDO1 start-up issue please?  We have measured it on board with/without SOC (66AK2G12) and there is still overshoot somewhere around 2.2V high. On our board as well as on evaluation board this LDO1 is used to supply all PLLs (AVDDA_ARMPLL, AVDDA_DDRPLL... AVDDA_UARTPLL). All PLLs has according to datasheet absolute maximum rating 1.98V. The overshoot seems like violation of that rating.

Best regards

Kamil

  • 0
    TI__Genius 10885 points

    Hi Kamil,

    Those Absolute Maximum Ratings are specifically for "Supply steady state voltage ranges". The notes for that table states "Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability". This condition is not steady state, and is instead an overshoot lasting for <200uS, which was considered acceptable for the evaluation board.

    This behavior is likely a combination of the LDO's inability to sink current and the use of an internal feedback connection. The only adjustable factors are the external layout and components. Reducing trace inductances on the PLL domains would be most beneficial.

    Best Regards,

    Rick S.

  • 0
    TI__Mastermind 33320 points

    Hi, Kamil,

      Thanks a lot for using our devices! 

      This is a known issue and has been validated; it is not a real problem; not cause any failure as long as the overshoot up to 2.2V is less than 100uS period.

      We're going to revise the specs to change it from current maximum ratings 1.98V to 2.2V with condition of "overshoot period less than 100uS".

      

  • 0 in reply to Richard Solarski
    Prodigy 140 points

    Hi Rick,

    thanks for reply. Do you think it might be good idea to supply these PLLs with LDO2? LDO2 start up seems to be ok without any overshoot.

    Best Regards

    Kamil

  • 0 in reply to Phil Yi40
    Prodigy 140 points

    Hi Phil,

    Thanks for reply. Do you mean that there will be new datasheet revision? If so when we can expect the revision to be released?

    Best regards

    Kmail

  • 0 in reply to Kamil Kazelle
    TI__Mastermind 33320 points

    Hi, Kamil,

      You can expect the revision to be released by the end of Nov. 2019.