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TPS659037: OFF2ACT sequence time for TPS6590378 LDOUSB output

Satoshi
Guru 19645 points
Part Number: TPS659037
Other Parts Discussed in Thread: AM5728

Below User's guide Figure-8 is described that LDOUSB output delay is 550μs.

https://www.ti.com/lit/ug/sliu011f/sliu011f.pdf

But below thread is described LDOUSB: 215μs internal delay.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/657045/tps659037-power-on-sequence-issue/2413551

Please let me know about the mean of above two specification and which one should be referred. 

I guess that LDOUSB delay based on 215μs +α and keep less than 550μs, correct?

Concretely, one customer's LDOUSB output delay is 250μs.

Is it no problem? 

Best regards,

Satoshi

  • 0
    TI__Genius 13216 points

    Hi Satoshi-san,

    I believe the interpretation is that in OTP of the part referenced in that manual, LDOUSB should have a 550us delay after the previous signal. However depending on the specific part number there may be different output delays. I believe the answer in the linked E2E thread refers to an internal analog startup time.

    Thanks,

    Daniel W

  • 0 in reply to Daniel W
    Guru 19645 points

    Hi Daniel

    Thank you for reply,

    I understood LDOUSB should have 550μs delay.

    Please let me know about related OTP information for LDOUSB delay time.

    I looking for the reason of LDOUSB become short delay time, but I didn't find on TPS659037 register map.

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Genius 13216 points

    Hi Satoshi-san,

    Please provide the OTP Marking on the top of the device for further clarification.

    Thanks,

    Daniel

  • 0 in reply to Daniel W
    Guru 19645 points

    Hi Daniel

    I attached TPS6590378's OTP marking below;

    Please let me know if you have any notices.

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Genius 13216 points

    Hi Satoshi-san,

    I agree for that OTP, LDOUSB should come up 550us after REGEN-1. However, the other E2E thread does mention that LDOUSB has more variance in timing than the other LDOs. I agree with your interpretation of that note.

    In order to get more information about the effect of timing variance on processor startup please start another thread for the processor you are using.

    Thanks,

    Daniel W

  • 0 in reply to Daniel W
    TI__Genius 13216 points

    Hi Satoshi-san,

    Please request a scope shot of the startup of REGEN1, LDOUSB, LDO1, and RESET_OUT,

    Thanks,

    Daniel W

  • 0 in reply to Daniel W
    TI__Genius 13216 points

    Hi Satoshi-san,

    Please refer to figure 5-2 of the AM5728 datasheet for more information about the processor side timing requirements. It appears that as long as LDOUSB is coming up after the vddshv1-11 rail and at least 1ms before rtc_porz it will satisfy the timing requirements.

    https://www.ti.com/lit/gpn/am5728

    Thanks,

    Daniel W

  • 0 in reply to Daniel W
    Guru 19645 points

    Hi Daniel

    Thank you for many advice,

    I attached scope shot of the startup, please see below;

    ・500μs/div, +3.3D_ON=REGEN1, VUSB_3V3=LDOUSB_OUT, VDD_SD=LDO1_OUT

    ・Zoomed the startup timing of LDOUSB_OUT (100μs/div)

    Compare with user's guide (below), actually LDOUSB_OUT and LDO1_OUT startup are occur 250μs delay.

    RESET_OUT startup timing look like 500μs later after LDOUSB_OUT startup. 

    Please let me know if you have any notices.

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Genius 13216 points

    Hi Satoshi,

    From this scope shot it appears that LDOUSB is acting as described in the thread referenced by you in the original post. It comes up at the same time as LDO1 as described in the user's guide, except with the expected ~215us delay described by Karl in the other thread. Additionally, RESET_OUT has the proper delay after LDOUSB as described in the user's guide. It appears to be functioning within expectations.

    Thanks,

    Daniel W