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LM48511 No output from H-Bridge

Mark Dimattina
Prodigy 10 points
Other Parts Discussed in Thread: LM48511

Hi,

Occasionally when the LM48511 Class-D audio amp starts up there is no output from the H-Bridge. The boost converter still works and the analog amp still works but the output on LS+ and LS- is low. This seems to occur when there is a break in the power supply. If the supply to VDD slowly drops to ~0.3-1V and the power is then restored the H-Bridge appears to lock up. I can reduce the likelihood of this happening by loading the VDD supply so it falls quickly.

 Is it possible to stop this from happening?

  • 0
    TI__Expert 3350 points

    Mark,

    I have not seen that, but I’m not surprised.  The boost has a minimum operating voltage of 3V, below which, the part will not function properly.  1V is well below the min supply.  Unfortunately, there is no UVLO or POR on this part which would solve the problem.  What I would recommend to use a comparator to monitor VDD, and shutdown the 48511 when the supply drops below 3V.  That way the part will be in a known state when the supply drops out.

    Regards,

    royce