TPA3136AD2: TPA3136AD2: Magnetic field causing fault continued

Jacob Wyrick

Part Number: TPA3136AD2

Hi team,

There was an issue in responding to the previous thread. Created a related thread to keep the conversation going!

Derek asked:

"What's the output power when issue happened? I think when magnetic field is close to inductor, it will lead current shake. You can monitor the current waveform when issue happen to double check it"

The response that was unable to be uploaded is:

"The output power is about 4.75W. I watched the current while I put a magnet by the inductors and I didn't see anything strange happen, it just shut off".

Thanks,

Jacob

over 3 years ago

0 Yanming Gong over 3 years ago

TI__Mastermind 19840 points

Hi Jacob,

Did you capture any current pulse?

When you remove magnet and toggle SD pin, can TPA3136 recover?

Regards,

Derek,

0 Jim Stewart over 3 years ago in reply to Yanming Gong

Prodigy 50 points

Hello Derek,

I didn't capture the current pulse, but I will set it back up and do that. To answer your second question, we have the FAULT pin tied to the SD pin so it does recover on it's own when I remove the magnetic field.

Thanks,

JIM

0 Jim Stewart over 3 years ago in reply to Jim Stewart

Prodigy 50 points

Here is what the speaker current looks like at the point the FAULT pin goes low...

0 Yanming Gong over 3 years ago in reply to Jim Stewart

TI__Mastermind 19840 points

Hi Jim,

According to the waveform, it is not OC fault.

You can short input pins to ground through 1uF capacitors, then check if the issue can reproduce.

Regards,

Derek

0 Jim Stewart over 3 years ago in reply to Yanming Gong

Prodigy 50 points

Hello Derek,

Just so I am clear, you want me to connect a 1uF capacitor from the inputs to ground as shown below...

Is this correct?

Thanks,

JIM

0 Yanming Gong over 3 years ago in reply to Jim Stewart

TI__Mastermind 19840 points

Hi Jim

Yes. correct.

Regards,

Derek

0 Jim Stewart over 3 years ago in reply to Yanming Gong

Prodigy 50 points

Adding a 1uF on the inputs to ground did increase the inductors immunity to the magnetic field, but did not eliminate it. However, adding the caps to the inputs dropped my output current from 1A peak to about 250mA peak. I also found that just reducing the input signal without the caps also increased the inductors immunity to the magnetic field.

Thanks,

JIM

0 Yanming Gong over 3 years ago in reply to Jim Stewart

TI__Mastermind 19840 points

Hi Jim,

Adding caps on input pins to ground means that there is no audio input, so no current on output. And you reduced the input signal also reduced the output current.

I suggest you can monitor the inductor current, red mark on below picture(between inductor and capacitor). I still think there will be pulse current when issue happened.

Audio

Audio forum

TPA3136AD2: TPA3136AD2: Magnetic field causing fault continued