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TAS5805M: The current pulse off TAS5805M PVDD

Mickey Lee
Prodigy 130 points

Part Number: TAS5805M

Hi TI team,

   I uses one boost converter IC to generate 14VDC for TAS5805M's PVDD exclusively; 

   there's a significant current pulse off the TAS5805M's PVDD domain every 12ms (I measured the current drawn by the booster input voltage 7.8V instead of PVDD) even though our device didn't perform playback:

  - the current pulse height of 7.8V input voltage (from 2-cell Li-ion battery pack)  was around 1.45A, that means the 14-V PVDD current pulse was around 0.725A

    (I posted three waveform pictures based on different current & time scales)

  - the current pulse width was around 1.0ms

  - the schematic of TAS5805M was attached in here as well

  we wonder whether there's wrong register setting inside the TAS5805M which resulted in such issue?

Sincerely,

Mickey

M10_TAS5805M_00.pdfM10_TAS5805M_01.pdf

  • 0
    TI__Guru 61670 points

    Hi Mickey

         The register settings won't affect the PVDD current so much. When you don't Play anything, there would be only DC current input with very low value. When you play a sine wave, you'll find a ripple current with the frequency of double the sine wave frequency. As the picture below shows a normal current. You can use a DC voltage source to power our device, and test the current.

        I think this waveform is more likely caused by the boost converter. Carefully examine the feedback loop of this boost converter, how about the current limit of this converter? Also, when the current have such big change, the voltage usually won't be very stable. You can also check the boost converter output, maybe the voltage and the current are both abnormal.

  • 0 in reply to Shadow He
    Prodigy 130 points

    Hi Shadow,

      The output current capability of our boost converter IC is 4.5A, besides the 14V voltage level was stable even though the weird current pulse took place.

      I also observed the current consumption off both PVDD rails (for woofer and tweeter driver respectively) and saw each PVDD has synchronous current pulse to booster IC's input even the /PDN pin of TAS5805M was driven to GND.

     

      First of all, we saw current pulse off each PVDD (CH2: PVDD_Woofer, CH1: PVDD_Tweeter)

    Second, the current pulse of each PVDD was synchronous to booster's input (CH2: PVDD_Woofer, CH1: booster's input)

     Moreover, we also found the surface temperature of TAS5805M IC was much higher even the TAS5805M didn't perform playback, then we removed

     the shunt CR components of each SPK output path (the EVM doesn't have the shunt CR parts either), as a result the surface of package obviously cooled down; what we measured above was based on such hardware configuration (none of shunt CR components mounted on our board).

    Are we still advised to use a DC power to supply PVDD instead, please?

    Thank you,

    Mickey   

  • 0 in reply to Mickey Lee
    TI__Guru 61670 points

    Hi Mickey

       It seems some resonance happens at the output side and affect the PVDD source. We can test the current flow through FB and compare with the PVDD current. We can also try to remove ESD diode and change the value of C903 to check if it helps. 

        We still think it may have some connection with their PVDD source, should try using a DC power as the PVDD supply.

  • 0 in reply to Shadow He
    Prodigy 130 points

    Hi Shadow,

       We removed ESD diode and change the value of C903, the current pulse still existed (the TAS5805M didn't perform playback);

       however we used a 14VDC power supply instead, this current pulse didn't happen,

       The synchronous booster needs to keep its output regulation, the current pulse of booster's input inevitably happens as long as its internal PWM

       controller turns on/off internal MOSFETs, as a result,  a resonance happens at booster's output side and affects the PVDD source, correct?

    Sincererly,

    Mickey 

       

  • +1 in reply to Mickey Lee
    TI__Genius 16370 points

    Hello Mickey,

    That seems to be the case that the output side resonance is affecting the PVDD source which is why you are seeing this behavior.

    best regards,

    Luis