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DLPA3005: Power Sequences

Expert 1185 points

Replies: 13

Views: 267

Part Number: DLPA3005

Hello,

I have an question regarding our developing DLP4710/DLPC3479/DLPA3005. DLPA3005 signals on our designed board looks like working fine. However, the power sequences looks incorrect. Can we allow below procedure?.

Datasheet shows :

Regards,

Uryyy

  • Hi Uryyy,

    It looks like PROJ_ON may be glitching high before SYSPWR is ready which is causing some unexpected and slow rising voltages. Is there anything else on the PROJ_ON rail that could be causing that glitch? Additionally has this been seen on just one of your boards or multiple boards?

    Thanks,

    Kyle

  • In reply to Kyle Rakos:

    Hi Kyle,

    Are you saying below circle? If so, we have to improve this point.

    Regards,

    Uryyy

  • In reply to Uryyy:

    In spite of PROJ_ON=OFF(Low), DLP4710EVM-LC is also same sequence.

  • In reply to Uryyy:

    Hello Uryyy,

    Yes, I am thinking it's possible the glitch circled on PROJ_ON could inadvertently be causing some issues like having the other voltages come up before the SYSPWR is stable. In the waveform where PROJ_ON is low the entire time do you see a glitch on it as well?

    Thanks,

    Kyle

  • In reply to Kyle Rakos:

    Hi Kyle,

    Yes, both of our designed board and 4710EVM are SUP_5P0V/SUP_2P5V=High after SYSPWR while PROJ_ON is low..

    Regards,

    Uryyy

  • In reply to Uryyy:

    Hi Uryyy,

    In the waveform where PROJ_ON is low the entire time do you see a glitch on it as well? Could you please share that waveform? I would recommend seeing if we can't eliminate the glitch. Perhaps you could temporarily add a capacitor on PROJ_ON to see if it filters out the glitch and the problem goes away. That could help us determine if it's actually the cause.

    Thanks,

    Kyle

  • In reply to Kyle Rakos:

    Hi Kyle,

    These are DLP4710EVM-LC power signals.

    Enlarged :

    Regards,

    Uryyy

  • In reply to Uryyy:

    Hi Uryyy,

    It is possible that the startup diagram is incorrect and SUP_5P0V and SUP_2P5V actually come up with SYSPWR. Please let me continue to look into this and I'll get back to you next week.

    Thanks,

    Kyle

  • In reply to Kyle Rakos:

    Hi Kyle,

    You can reproduce on EVM. I look forward to wait a good result.

    Regards,

    Uryyy

  • In reply to Uryyy:

    Hello Uryyy,

    We were able to see the same thing on our board. I think what is happening is that when SYSPWR comes on these rails slowly charge (possibly through some leakage) to some level. However, it's not until PROJ_ON goes high that the rails are actually regulated (you can see this in your waveform when PROJ_ON goes high these rails go a bit higher).

    In either case, since nothing should be externally on these pins (other than the proper cap) there should be no concern with this. This appears to be the expected operation.

    Thanks,

    Kyle

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