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TPA3255: TPA3255 fault pin goes low after a while of use.

Part Number: TPA3255

Hello,

I have built a circuit to drive a transducer operating on a sine wave of approx. 20 kHz.
The transducer impedance is not constant.The transducer is connected to the circuit via a transformer.
The impedance from the primary side of the transformer seen will be approximately 4 Ω to several tens of Ω.
The transducer requires a maximum power of approximately 150 W.
The power supply for PVDD is 48V 300W.
Actual measurements show that a maximum current of approximately 3A flows in PVDD.
TPA3255 is operating in PBTL mode.I built the circuit using TPA3255EVM as a reference.I will post the schematic.


TPA3255 has a heat sink attached.
This heat sink is about 1.5 times larger than the heat sink installed on the TPA3255EVM,
and a heat exhaust fan is also installed.

This circuit can be operated for several hours without any problems,
but problems occur when this circuit has been in operation for several weeks.
When the current flowing into PVDD is less than 1A, no problem occurs.
When the flowing current exceeds 1A, the fault pin goes Low and operation stops.
When TPA3255 is replaced with a new one, it works fine.
So I think TPA3255 is malfunctioning for some reason.
What could cause TPA3255 to fail?


Thank you,

Nishimura

  • Hi Nishimura.

    It seems that your schematic is okay.

    Do you mean the FAULT pin is low and CLIP_OTW pin is high?

    If it is, you can take a check that if there is a OLP or UVP when fault happened.

    BR.

    Wei Qiu.

  • Hello,

    I'm sorry for the late reply.

    The Fault pin is Low and the CLIP_OTW pin is High when a problem is occurring.

    I was reviewing photos of the malfunctioning board that I had taken beforehand.
    Looking closely at the photos, it looked like pin 32 of TPA3255 had a solder defect.
    I re-soldered the TPA3255 that I thought was defective firmly again and it now works fine.
    So it seems that the Fault pin was low due to poor contact.

    Thank you,

    Nishimura