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TPS274160: Questions regarding toggling of EN and DIAG_EN

Darren (FAE)
Expert 5483 points
Part Number: TPS274160

We are considering an application for TPS274160.
For the sake of argument, let's consider only using 1CH (the other 3CH are disabled); in this case:

1) Let's assume DIAG_EN = 5V // EN = 0V // xST = LOW (reporting open-load fault)
a) From this state, how long after enabling the channel before the "LOW" reverts back to "Hi-Z"?
(Does it happen instantly on the rising-edge of the enable signal?)

2) I don't see any info on timings when DIAG_EN is brought from LOW -> HIGH while the channel is already enabled.
How long does it take for the diagnostics circuitry to "turn-on"?
Is this an allowable use-case?

3) One application we are considering this device for would just use a single channel (3-channels would be disabled)
For this application, we'd like to drive the EN and DIAG_EN signals together; so there is no open-load reporting when EN = LOW.
Are there any concerns related to this? It seems acceptable, but it is hard to understand priority/timing requirements.

Regards,
Darren

  • 0
    TI__Genius 16390 points

    Hi Darren,

    Let me try to answer the questions.

    1) Yes, with some propagation delay.

    2) For the current sense feature, it would be 20us for it to settle from the DIAG_EN.

    3) It's a valid use case. Do you have specific concerns somewhere?

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    TI__Expert 5483 points

    Hi Yichi,

    1) That delay is what I'm after, any estimate of how much? are we talking [ms] or [us]?

    2) I need to know that value for the "A" version with open-drain. Is it the same? If so, why only validate for CS pin?

    3) Specifically concerns are around the fault reporting timings in this case.

  • 0 in reply to Darren (FAE)
    TI__Genius 16390 points

    Hi Darren,

    1) it would be in us range.

    2) For version A, during ON state, the only diagnostic feature is the fault reporting at the ST pin. It would be in us range as well. As we don't have this data internally as well, we suggest customer to test on an EVM to confirm and make sure it's acceptable. Device will still have the full protection regardless if DIAG_EN is ON or OFF.

    3) I see. The delays should all be in us range. Is there a specific timing target the customer is trying to meet?

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    TI__Expert 5483 points

    Hi Yichi,

    It looks like there is "Standby Mode with Diagnostics" and "Standby Mode"

    I understand taking DIAG_EN "LOW" while EN = 5V will result in open-load detect output to xST after the deglitch time (>300us)
    But after EN goes low, the device enters standby mode after ~10ms.

    If EN and DIAG_EN are taken "LOW" at the same time, will we still get open-load detect output after the deglitch time (>300us) before standby happens ~10ms later? Or will there be no open-load detect until standby mode has been entered?

  • 0 in reply to Darren (FAE)
    TI__Expert 5483 points

    Hi Yichi,

    On top of my previous question about standby mode timings...

    [1]
    Can the DIAG_EN pin handle constant toggling, like the EN pin, with no impact on device operational lifespan? (Yes/No?)

    [2]
    If DIAG_EN and EN are taken LOW at the same time, I understand from "tcs,off1" that diagnostics will be disabled within 20[us].
    This number is for the "B" version(CS), but does it also apply to the "A" version(open-drain)?

    [3]
    When DIAG_EN and EN are taken HIGH at the same time, I understand from "tcs,on2" and "tcl(deg)" that the open-drain fault output of the "A" device
    will take (<150[us] + <180[us]) ≦ 330[us] to toggle and indicate an overcurrent/TSD event. Is this understanding correct?f
    Again, this is using numbers in the datasheet for the "CS" version - do these also apply to the "A" version?

    Regards,
    Darren

  • 0 in reply to Darren (FAE)
    TI__Genius 16390 points

    Hi Darren,

    For the question regarding the standby mode: it will indicate the open-load after the t(ol)off before entering the standby mode.

    For the follow-up questions:

    1) No problem toggling DIAG_EN pin.

    2) For Fault indication, it would be faster than 20us. It would be in a couple us range.

    3) The fault indication should not have the extra tcs,on2 time. It would be around tcl(deg) plus a few us of propagation delay. 

    Please let me know if this makes sense.

    Regards,

    Yichi