TPA3136AD2: Do not get the GAIN of 20X but instead only 10X

grant juel1

Intellectual 480 points

Part Number: TPA3136AD2

The part says 26dB fixed GAIN is what I should see. I am only seeing a GAIN of 10X

over 3 years ago

0 Yanming Gong over 3 years ago

TI__Mastermind 19030 points

Hi Grant,

Can you please share your test data and your test setup?

Thanks!

Regards.

Derek

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

Please explain your question.

I put in a 500mVppk signal and only get out of the LC filter 5Vppk (approximately those values). I look at this signal with an o'scope

0 Yanming Gong over 3 years ago in reply to grant juel1

TI__Mastermind 19030 points

What's the PVDD value?

Is the output clippling?

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

PVDD is 11.2 vdc

The output is NOT clipping

I have PLIMIT set with same resistor values as shown on the data sheet

0 grant juel1 over 3 years ago in reply to grant juel1

Intellectual 480 points

0486.Oscope AudioAmp-DC mode.docx

0 grant juel1 over 3 years ago in reply to grant juel1

Intellectual 480 points

2728.Oscope AudioAmp-DC mode.docx

0 Yanming Gong over 3 years ago in reply to grant juel1

TI__Mastermind 19030 points

1. The Isat of inductor of LC filter is too low, only 1.2A.

2. For 500mV input, 26dB Gain setting, the output should be 10V. But the LC and trace loss must be considered.

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

When I supply a 500mVppk input sine (1600Hz) the output measured at the inductor/cap connection (into the speaker) is only 5Vppk (a GAIN of 10).

The trace length is only 1/2-3/4" long so would you consider this to be significant?

What inductor saturation current would you suggest?

0 grant juel1 over 3 years ago in reply to grant juel1

Intellectual 480 points

I replaced all four inductors with one that is rated for 3Amps. The GAIN remains the same as 10X

0 Yanming Gong over 3 years ago in reply to grant juel1

TI__Mastermind 19030 points

Please using sine wave audio input, and monitor the audio input and output (close to LC filter as possible) waveform.

If you have problem, please send the monitor waveform to us.

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

I am using a 1600Hz sine wave for the signal. I am measuring at the LC junction.

See attached oscope for signal in and signal out 1600Hz Sine.docx

0 Yanming Gong over 3 years ago in reply to grant juel1

TI__Mastermind 19030 points

The NC pin should be floating, especial the pin #5.

Please NC the pin #5 and try again.

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

Floated pin 5. No change in the GAIN ...this at 5vppk (PVCC is at 12.2vdc)

Then floated pin 6 also.......... No change in the GAIN....this is still at 5vppk (PVCC is at 12.2vdc).

Will now float pin 13................. nope..........No change in the GAIN

0 grant juel1 over 3 years ago in reply to grant juel1

Intellectual 480 points

How best to determine the optimum Inductor and Capacitor to be used on the Audio Output? Currently I am using 10uH and 2.2uF for the LC.

0 Yanming Gong over 3 years ago in reply to grant juel1

TI__Mastermind 19030 points

I think there must some thing wrong.

Please use sine wave input and check the unclipping output together.

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

Sine Input for TPA3136AD.docx

0 grant juel1 over 3 years ago in reply to grant juel1

Intellectual 480 points

Using a NEW PCA....... I changed the Inductor (4) to be the 3A part. Floated pins 5,6,13. I also tied PLIMIT to GVDD (solder bridged the pins)

Then used a Function Generator to supply the sine wave. This was AC coupled into RINP

Result: NO CHANGE from what I have been seeing. The input was 500mVppk The output was 5Vppk (no clipping)

0 Yanming Gong over 3 years ago in reply to grant juel1

TI__Mastermind 19030 points

For Gain setting question, you should check voltage difference (OUTP-OTPN) ,not only OUTP/N.

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

What do you mean by using the "dividing" symbol?

The o'scope plots show both the OUTP and OTPN..........the difference is clearly seen..........and that difference is 10X the input. What do you mean by OUTP/N ....I am not dividing the Positive output by the Negative output............ Please explain.

0 Yanming Gong over 3 years ago in reply to grant juel1

TI__Mastermind 19030 points

The last picture shows only OUTP waveform!! only 8Vpp.

You must check OUTP-OUTN, it must 8V+8V=16Vpp!!

I have explained many times, please do not only check one pin(OUTP or OUTN)!

You can also check the power using AP instruments! The power must make sense!

0 grant juel1 over 3 years ago in reply to Yanming Gong

Intellectual 480 points

800mVppk to 16Vppk.docx

0 grant juel1 over 3 years ago in reply to grant juel1

Intellectual 480 points

I used a sine wave for the input and then used a digital voltage meter to measure the Vrms for the input....and then for the output.

Input 290mVrms

Output 5.72Vrms

.........therefore the GAIN is 19.6

The main issue was that of not looking at the speaker drive voltage properly.

CASE CLOSED

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TPA3136AD2: Do not get the GAIN of 20X but instead only 10X