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CSD95490Q5MC: Where should "EN" pin come from?

user4811888
Intellectual 530 points
Part Number: CSD95490Q5MC

If seen from typical application circuits in TI multi-phase controller, EN pin sometimes come from 3.3V(from controller internal LDO output,V3R3), sometimes come from 5V(CSD95490 power supply itself).

I'm really confused, is there any special consideration here? Why not use 5V in all designs? Or, why not use 3.3V in all designs?(not matter coming from controller VCC, or 3.3V controller internal LDO output)?

  • 0
    TI__Expert 3525 points

    Hi,

    Thank you for your interest in CSD95490.

    The EN pin is compatible with both 3.3V and 5V design, you can choose either one depending on the availability in your system. We suggest to use clean voltage signal to drive this pin to prevent false triggering the EN pin.

    Best,

    Qingquan

  • 0 in reply to Qingquan Tang
    Intellectual 530 points

    Hi,

    Thank you for your answer, but voltage range is not what I'm concerning about. In my opinion, the key point here should be the driving source(who gives the signal to EN).

    Isn't the signal sequence important here? I suggest to think over this question more and deep together.

    Figure out all the connection options as below. Do you mean that, all these four options(two for case 1, and two for case 2) are all okay when we design? 

    In case 1, 3.3V must be later than 5V ready. But in case 2, 3.3V and 5V are independent.

  • 0 in reply to user4811888
    TI__Expert 3525 points

    Hi,

    Thank you for clarifying your question.

    For power up sequence consideration, we have the following suggestion:

    3.3V supply for controller -> 5V supply for PS -> PS EN ->12V input -> VR_EN

    The power down sequence can be reversed from the power up sequence. 

    The suggested sequence can prevent start up in-rush current, and the controller can monitor the complete power-up procedure, fault protection and fault recording.

    Best,

    Qingquan

  • 0 in reply to Qingquan Tang
    Intellectual 530 points

    Appreciate it for pointing out sequence recommended, but I'm thinking that it only makes sense for 3.3V supply controller in your words.

    As you know, some controllers are supplied by 5V, that means controller and PS both are powered by the same 5V.

    Then, could we move PS EN to this 5V also(case 1→option 1 in my figure)? 

  • 0 in reply to Qingquan Tang
    Intellectual 530 points

    Simplify my question for easy understanding:

    Can I connect PS EN to 5V supply, when used with 5V supply controller? (PS EN was originally connected to V3R3 from controller) 

  • 0 in reply to user4811888
    TI__Expert 3525 points

    Although controller also supplied by 5V, there might be delays on 5V bus, which still needs some attention to verify.

    To answer your question, we need to make sure the PS_EN is always activated before VR_EN and have some buffer time between. It's also suggested to have controller supply voltage ready before PS_EN activated.

  • 0 in reply to Qingquan Tang
    Intellectual 530 points

    Got it, thank you. I will think it over.