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TPA3251D2EVM: Auto Shutdown after a few secs of music play

Part Number: TPA3251D2EVM

Steve. I have been following this thread with some interest as I have completed our new design for an amplifier using much of the EVM layout guidelines along with the SE to DIFF opp amp circuit. Our design is BTL. The point I am interested in is the observation you made regarding the C start cap value. The EVM schematic shows 100nf for BTL mode but for us we are getting the amplifier fire up and play music for a few seconds then shut down. The current draw is no more than 120ma during the working period dropping to 5ma when shut down kicks in.

Power supply is 20v from a benchtop supply at present but on the PCB we have incorporated the made linear power supply to provide the PVVD at 26V with large 6800uF 80V caps across the rails. 

We have left the reset pin unconnected but other than that we have pretty much duplicated the EVM schematic and PCB layout. Its quite a disappointment at present as we are not sure how to resolve the issue. would appreciate some assistance as we are waiting on the design to finalise a product for production this summer using a PCB full of TI products.

hope you can help. If I have posted this question and broken any rules I apologise as this is only the 2nd time I've posted.

I have schematic and layout gerbers if you would like to see them.

cheers

John

  • John,

    I received your schematic via PM and will respond there.

    best regards,
    -Steve Wilson
  • Just to provide a solution to this issue for future reference:

    The problem in this case was the Reset pin was left floating. This is a problem as the Reset pin does not have an internal pull up resistor.

    Additionally, to avoid pops/clicks on power up and power-down TI strongly recommends that our customers use some kind of power supervisor IC such as the TPS3802 as we do on the TPA32xx Evaluation modules. This IC will put the amplifier into reset before the power dips too low, allowing the amplifier to perform a controlled ramp down of the outputs. Alternately, use a microcontroller, which will have its own power supervisor, and can put the amplifier in reset as part of its shutdown routine.

    best regards,
    -Steve Wilson