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TAS5825M: PVDD condition

Kazuki Kuramochi
Genius 12385 points

Part Number: TAS5825M

Hello expert,

I have question regarding PVDD.
We would like to supply power for PVDD pin when DVDD is turned off.
I think there is any concern as long as maintain above condition but I'd like to confirm this with you just in case.
Is there any concern?

Also, recommended start-up/shut-down sequence on datasheet is turn on/off PVDD and DVDD simultaneously.
However, above situation cause the violation of this sequence.
What will be caused by this violation?

I'm looking forward to hearing back from you.



Thank you and best regards,
Kazuki Kuramochi

  • 0
    TI__Genius 9995 points

    Hi -san,

    You mean that you would like to supply power for PVDD pin when DVDD is turned off. Is it for power on or power down?

    On Ti recommended sequence: for start-up, PVDD and DVDD do not have sequence requirements. You can start up PVDD first when DVDD is off.

    For power-down sequence, you can see PVDD (4.5V) and DVDD also has not requirements for sequence.

    Please clarify more clearly if my understanding is not correct.

    BR,

    Alix 

  • 0 in reply to Alix Wan
    TI__Genius 12385 points

    Hi Alix-san,

    At first, I'd like to confirm whether there is any issue under the condition that is supplying PVDD but  DVDD is turned off.
    I think there isn't any problem as far as we meet the datasheet's recommended supply voltage from the point of view of damaging device if we considered only this condition.


    But, I realized we need to consider how to make above condition.
    I think there is 2 procedure of making above situation as following.

    Case 1: All power rail is turned off -> Turn on PVDD
    Case 2: All power rail is turned on -> Turn off DVDD
     
    Also, After first question's condition, Device's Turn on procedure would be above if the want to turn on the device.
    Case 3:PVDD is turned on -> Turn on DVDD

    As for case1 and case 3, I understood there is any problem in spite of datasheet's start-up sequence require to turn on PVDD, DVDD and \PDN simultaneously.
    In regard to case 3, I think this 4.5V limitation is for preventing unexpected behavior of switching stage from the unstable DSP and gate driver stage?

    Anyway, I understood we cannot guarantee  normal operation under Case 2.

    Thank you and best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Genius 9995 points

    Hi Kuramochi-san,

    As to case 2, your understanding is correct. 

    In order to ensure the safety of power down, PDN /Hiz is required 6ms before PVDD/DVDD turns off,  which aims to avoid unsure status when power rail turns off.

    But, as you konw, chances are that customer may not be able to turn PDN down or make device into Hiz on certain conditions. Hence PVDD drops to 4.5V below, which triggers the under-voltage protection and turn off power stage. Then DVDD can power off without risk.

    BR,

    Alix Wan.

  • 0 in reply to Alix Wan
    TI__Genius 12385 points

    Hi Alix-san,

    Thank you for your support.
    I understood.

    Best regards,
    Kazuki Kuramochi