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TAS5630B: Shut down sequence

Mochi
Genius 4255 points

Part Number: TAS5630B

Hello,

Our customer is facing streng phenomes while power down of PVDD, before kick in UVP alert,  suddenly large short-though current is running as attached waveform.  
At that time GVDD and VDD are keeping 12V. This problem occurred with 10% of device probability. 

TAS5630B PVDD.pdf  

As a datasheet described: 7.3.2.2 Powering Down The TAS5630B does not require a power-down sequence. The device remains fully operational as long as the gate-drive supply (GVDD_X) voltage and VDD voltage are above the undervoltage protection (UVP) voltage threshold (see Electrical Characteristics). Although not specifically required, it is a good practice to hold RESET low during power down, thus preventing audible artifacts including pops or clicks. 

What are those 10% failed device function?

Regards,

Mochizuki

  • 0
    TI__Mastermind 21830 points

    Hi Mochizuki,

    Is the device being damaged while powering down in this scenario? Is there an input signal to the device while being shutdown? 

    Regards,

    Sebastian 

  • 0 in reply to Sebastian Muriel
    Genius 4255 points

    Hi Sebastian,

    It is no matter what the input signal is, but H-bridge itself flows large current >15A. One additional information is that working mode is PBTL, mixing output signal at the post LPF node and it has occurred at certain #LTC device only. Do you see simier issue prviously?

    Regards,

    Mochizuki

  • 0 in reply to Mochi
    TI__Mastermind 21830 points

    HI Mochi,

    So to confirm the device is being damaged while powering down? What is the load at the output?

    Does this issue also occur without the output filter? 

    Regards,

    Sebastian

  • 0 in reply to Sebastian Muriel
    Genius 4255 points
    Hi Sebastian,
    Atfter a few traial of this PVDD UVP experimants finaly the device is parmentry damaged. We can see PVDD short current is vary more than 15A-17A range, there is no OCP activation.
    The load is 2ohm on PBTL mode, we did not try to disconect LPF.  The inductoer has enough current handring during normal operation.
    Regards,
    Mochizuki
  • 0 in reply to Mochi
    TI__Mastermind 21830 points

    Hi Mochi,

    How are you measuring current flow into PVDD? 

    The OCP threshold is a DC specification, while you're describing a transient current spike. 

    Also 2Ohms is below the minimum recommended load impedance in PBTL for this device. 

    Regards,

    Sebastian

  • 0 in reply to Sebastian Muriel
    Genius 4255 points
    Hello Sebastian,
    We think that is kinds of true, it seems H-bridge itself creates large transient sink current flow from PVDD supply during the system Power-down sequence.  
    In our understandings OCP trip point is specified/measured at H-bridge FET Source leg current include Inductor PWM ripple and output signal.
    The issue is that behavior looks like H-side and L-side FET turn on at same time when PVDD is dropping around 9V, it no matter what input signal and load are.   
    Sine 10years this equipment is produced without this phenomenon but certain #LTC device shows this problem.
    Regards,
    Mochizuki
  • 0 in reply to Mochi
    TI__Mastermind 21830 points

    Hi Mochi,

    So the device is damaged or is the device going into shutdown mode and can be reset? 

    I'm still curious as to how you're measuring this current flow... I only saw voltage waveforms in the scope shot. 

    Ultimately if this issue is resolved by swapping a good unit from a different LTC, then this would indicate devices from that LTC could be misbehaving. You can submit a customer return through the customer support center  and we can throughly investigate if the device is malfunctioning. 

    Regards,

    Sebastian 

  • 0 in reply to Sebastian Muriel
    Genius 4255 points

    Hi Sebastian,

    Thank you for your suggestion.
    We have the current probe measurement data beside of voltage waveform.
    Some of devices show more than 15A and finally get permanent damage, no function at the next power up sequence.
    The other devices are not reach15A and keep working at the next power up.   
    We will contact costumer support center.
    Regards,
    Mochizuki
  • 0 in reply to Mochi
    TI__Mastermind 21830 points

    Hi Mochi,

    Just curious what was the current spike you measured with the known good devices?

    Noted on contacting customer support, they will ask for some information to move forward wtih the return.

    Regards,

    Sebastian