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About fast response sequencer

Satoshi
Guru 19485 points
Other Parts Discussed in Thread: LM3880, TPS53318, LM3881, UCD9090

Is there sequencer device of faster UVP and UVLO than LM3880?

【Background】

・LM3880 sequencing TPS53318

・When occur the momentary power failure(1ms), TPS53318 is UVLO-shutdown(VREG), but LM3880 is keep on moving.

  ⇒I looking for fast response sequencer. (less than 1ms)

    The goal is; also LM3880 and TPS53318 keep on move when 1ms-voltage drop.

【Ideal function】

①Sequence control is three line, these delay time is 10ms.

②If EN (or Vcc) voltage dropped less than 1ms, at first power down sequence is move.

③If EN (or Vcc) voltage return, power up sequence is move.

※② and ③ are LM3880/3881 normal operation, but ①is difficult for LM3880/3881.

Best regards,

Satoshi

  • 0
    TI__Intellectual 2010 points

    Hi Satoshi,

    ・When occur the momentary power failure(1ms), TPS53318 is UVLO-shutdown(VREG), but LM3880 is keep on moving.

    The UVLO threshold for TPS53318 is 3.95V and if the voltage droops below that, the device will enter shutdown mode. LM3880 doesn't have UVLO. As long as the EN is above 1V, the Flag voltage will remain high from the flag supply. This be because the internal FETs are ON due to EN high. So LM3880 cant enter UVLO. 

    ①Sequence control is three line, these delay time is 10ms.

    LM3880 is perfect candidate for it because it can provide 10msec delay sequence . TI also have other more complicated sequencers like UCS9090, but I believe that would be overkill for this application

    ②If EN (or Vcc) voltage dropped less than 1ms, at first power down sequence is move.

    ③If EN (or Vcc) voltage return, power up sequence is move.

    If EN is dropped, the Flag voltage will sequence down in 2msec for LM3880. This is the fastest power down sequence time it can offer. However, if you are VCC and EN are tied together without, the power down sequence will be fast. All flags will drop as soon as VCC drops down. Power down sequence only works if your configuration is as follows:

    For 3, once the VCC and EN is re-established, the Flags voltage will return withing 2msec for LM3880 and this is programmable for LM3881

    1 is possible with LM3880 following ordering code:

    Hope this helps.

  • 0
    TI__Intellectual 2010 points
    Another important thing is LM3880 first flag turn ON (After EN ON) is factory programmable and can be reduced down from 2msec to 1 msec as your application requires. However the minimum delay between each flag is 2msec.
  • 0 in reply to Kaisar Ali
    Guru 19485 points
    Kaisar Ali-san

    Thank you for detailed reply.
    I think that solution idea of meet "①②③ all" is only UCD9090 (or UCD series), is it correct?
    I happy if there is TPS38xx series solution of meet ①②③ all, but I feel very difficult.

    Best regards,
    Satoshi