TPA3131D2: Fault keep high/ low cycle change during start up

Ben Kuo

Expert 7490 points

Part Number: TPA3131D2

Tool/software:

Hi expert,

Customer recently face to random no audio output issue after power up in MP project.

The project is mass production for a long time, and recently have two boards don't have audio output.

We have measured fault pin and find fault pin is in low<-> high cycle. We have checked the failed condition which may trigger to fault, but there are no short circuit/ over current/ DC offset/ etc. fault. Also find an e2e post which talking about input cap quality, we test it and measured the waveform but no failed been found.

The fault pin will keep high(have audio output) after system run in window and then change sound volume.

Since we only have two failed board on hand. Before do ABA swap test. Any waveform measurement we can do to verify issue root cause?

Regards,

Ben

22 days ago

0 Ivan Salazar 21 days ago

TI__Guru** 102755 points

Hi Ben,

Is there a schematic we can look at?
I would test by disconnecting the speaker, and check if the behavior is the same. Also check both input and output signals including DC, perhaps this is DC offset fault.

Best regards,
-Ivan Salazar
Applications Engineer

0 Ben Kuo 19 days ago in reply to Ivan Salazar

TI__Expert 7490 points

Hi Ivan,

Please find schematic here.

MLC-S _ 48_AMP+SPK CONN.pdf

We have disconnect speaker and check input/ output signal. But there are no abnormal behavior.

Regards,

Ben

0 Ramsey Foote 19 days ago in reply to Ben Kuo

TI__Expert 5815 points

Hi Ben,

Our team has received your question. Responses may be a little slow due to the holiday season.

Thanks for your patience,

Ramsey

0 Jesse Ji 18 days ago in reply to Ben Kuo

TI__Genius 15440 points

hi Ben

you inductor value is so small. which might have large ripple current.

can you tell me your switching frequency?

also, what is your load resistor and output power?

tks

jesse

0 Liang Tsai 17 days ago in reply to Jesse Ji

TI__Intellectual 1500 points

Hi Jesse,

Thanks for the reply.

Customer is wondering how could we determine the inductance based on the ripple current. To my understanding, we can get the ripple by using the equation: ripple current = (Vin-Vout) x D x T/L where Vin is the peak input voltage on the left side of inductor and Vout is the average voltage that went through the LC filter. I was wondering if you could kindly verify it for me?

The switching frequency/load resistor/output power information is provided below:

The below table is the spec. of customer's speaker parts which is 3W@8ohm.

Customer's HW design is max. 4W@8ohm.

Best,

Liang Tsai

0 Jesse Ji 16 days ago in reply to Liang Tsai

TI__Genius 15440 points

hi Tsai

about the inductor how we select, you can refer 8.1.2 Inductor Selections in below link.

https://www.ti.com/lit/ds/symlink/tas5805m.pdf?ts=1735187587539&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTAS5805M

thanks.

jesse

0 Liang Tsai 9 days ago in reply to Jesse Ji

TI__Intellectual 1500 points

Hi Jesse,

Thanks for the information, it is really helpful. I have calculate the I_sat >= Max (I_peak_power_up, I_peak_clipping, I peak_output_power) based on customer's specification and got the value as Max(1.55A, 2.58A, 1A).

In the application note you sent me, it mentioned that the peak clipping current rarely happen, and customer is wondering if they could use inductor that its saturation current is at 2A max for this case. This product is already MP so they are limited to the inductor with same footprint which the highest saturation current is 2A max.

Thanks for the support.

Best,

Liang Tsai

0 Jesse Ji 8 days ago in reply to Liang Tsai

TI__Genius 15440 points

hi，Liang

in my understanding, 2A max still has the risk, maybe performing some reliability test with 2A inductor is better.

thanks.

jesse

0 Liang Tsai 4 days ago in reply to Jesse Ji

TI__Intellectual 1500 points

Hi Jesse,

I was wondering what reliability test should we go through?

Best,

Liang Tsai

0 Jesse Ji 3 days ago in reply to Liang Tsai

TI__Genius 15440 points

Hi,

please play some large audio signal under some thermal cycle to see whether the fault pin be triggered or not.

Too small Isat might lead to OC easy to happen.

thanks

jesse

Audio

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TPA3131D2: Fault keep high/ low cycle change during start up