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AM2634-Q1: Power-On and Reset Sequencing

teshima yohei
Prodigy 120 points
Part Number: AM2634-Q1

Power-On and Reset Sequencing

Datasheet: JAJSOB0
7.11.2.1 Power-On and Reset Sequencing
Figure 7-1. Power-On Sequencing

VDDS33 and VDDA33 are written as the same item, but is it necessary to start them at the same time?

The purpose of the question is that I want to connect different LDOs to VDDS33 and VDDA33, but I don't know the startup sequence in that case.
Or can VDDS33 and VDDA33 only be input from the same LDO?

Japanese memo

データシート:JAJSOB0
7.11.2.1 Power-On and Reset Sequencing
図7-1. Power-On Sequencing

VDDS33とVDDA33が同じ項目として書かれているが、同時立ち上げの必要があるのか？

質問の意図としては、VDDS33とVDDA33に違うLDOを接続したいけど、その際の起動シーケンスが分からへん。
それともVDDS33とVDDA33は同一のLDOからの入力しかできないのか。

  • 0
    TI__Intellectual 1900 points

    Hi Teshima Yohei,

    Apologies for the late reply. I am checking with the experts on this. I should have an answer in a couple of days.

    Thanks,
    Tejas Kulakarni

  • 0 in reply to Tejas Kulakarni
    TI__Intellectual 1900 points

    Hi Teshima Yohei,

    I checked internally and, the PORz reset is on VDDS33, therefore VDDS33 has to be the first one to ramp-up to keep device in a known state.

    Thanks,
    Tejas Kulakarni

  • 0 in reply to Tejas Kulakarni
    Prodigy 120 points

    Hello

    I understand that VDDS33 is ramped up before VDDA33.
    And I understand that VDDS33 and VDDA33 do not need to be ramped up at the same time, is that correct?

    In that case, the data sheet does not specify the time from when VDDS ramps up to when VDDA33 ramps up.
    Am I correct in understanding that there are no constraints other than tStartup and tRamp_3V3?


    thank you
    Youhei

    Japanese memo

    VDDA33よりもVDDS33を先にランプアップする旨は理解しました。
    そしてVDDS33とVDDA33は同時にランプアップする必要がないと理解しましたが合っていますか？

    そうなるとデータシートにVDDSがランプアップされてからVDDA33がランプアップするまでの時間が規定されていない。
    tStartupとtRamp_3V3以外の制約はないという理解でいいのか。

  • +1 in reply to teshima yohei
    TI__Intellectual 1900 points

    Hi Teshima Yohei,

    teshima yohei said:

    And I understand that VDDS33 and VDDA33 do not need to be ramped up at the same time, is that correct?

    Yes, the VDDS33 and VDDA33 need not be ramped up at the same time, but VDDS33 needs to ramp up before VDDA33 as mentioned earlier. Also please ensure to take care of tRamp_3V3 = 0.1ms(min) for both VDDS33 and VDDA33 since that is a required parameter.

    teshima yohei said:
    In that case, the data sheet does not specify the time from when VDDS ramps up to when VDDA33 ramps up.
    Am I correct in understanding that there are no constraints other than tStartup and tRamp_3V3?

    Yes, there is no requirement imposed between the ramping up of VDDS33 and VDDA33. But as again shown in Figure 7.1 of AM263x Datasheet, please ensure to have both VDDS33 and VDDA33 ramped up, with both their Power Good signals generated from those Voltage sources and only then ramp up PORz. The only constraints are mentioned in Table 7-2 of the datasheet itself, no other requirements are imposed.

    Thanks,
    Tejas Kulakarni