TPA3255: Fault stays low in PBTL configuration - RESET not working

Hi Thei Mnbs.

After I reviewed your schematic, I noticed that M0 and M1 seem to be reversed in your Schematic configuration.

If use PBTL mode, it should make M1=0 and M2=1, and should connect INC and IND to ground.

Could you try to change it first?

Wait for your feedback.

BR.

Wei Qiu.

Hi Wei Qiu,

You are right, my schematic is not correct (I changed it) however on the PCB M1 : GND and M2 : 3V3 (see above).

So the problem is not coming from there.

Any other idea ?

Regards,

Théo

Hi Théo.

This is indeed a strange question.

So under your configuration, when PVDD is lower than around 24V, it works normal?

Can you share us more related information?

Please provide the waveforms of input/ output(PWM)/ Fault/ OTW.(both normal and fault conditions)

Thanks.

BR.

Wei Qiu.

Hello Wei Qiu,

The power supply (PVDD) is indeed 24Vdc. I did not try higher voltage since TPA3255 should handle such power to start and work normally.

At the moment I've never been able to make the board work at all. I've always had /FAULT pin low, and RESET doesn't help.

I must check with an oscilloscope the output waveform. This only thing I can tell for the moment is that on the multimeter PWM_A = PWM_B = OUT_A = OUT_B = 7,9Vdc.

Best regards,

Théo

Hi Théo.

Théo Mnbs said:

PWM_A = PWM_B = OUT_A = OUT_B = 7,9Vdc.

This is abnormal.

We really need more information for further analysis.

Wei Qiu said:

Please provide the waveforms of input/ output(PWM)/ Fault/ OTW.(both normal and fault conditions)

Could you also provide the startup waveforms of input/ output(PWM)/ Fault/ OTW.

BR.

Wei Qiu.

Hello Wei Qiu,

Updates about the board issue, blocked in /FAULT mode.

When removing jumper (shorting IN_C and IN_D) the /fault pin goes high and the device starts to react almost normally (RESET working).
However, if I connect an audio source (sinus 440Hz), I don't see any PWM working at the output A or B of the amplifier.

Thus, it seems that shorting IN_C and IN_D to ground are problematic. 

Here is what I have when...

1) Power supply : PVDD=25V

2) JUMPER of IN_C and IN_D are not grounded

3) Audio is connected to the entrance : Sinus 440 Hz

Audio input at entrance: (see in schematic potential IN_GAUCHE or IN_DROITE)

Audio line after AO NE5532AD : (see in schematic potential IN_A= IN_B):

IN_C = 4V+AC. 

AC ripple is not affected by audio input : if removing 440Hz signal, AC ripple stays like it is.

Here is what I have on IN_D

Here is what I found on PWM_A & PWM_B:

I tried to short IN_C and IN_D with a 10kohm resistor in case a short circuit would cause an issue but this doesn't help.
If I short (with a jumper or 10kohm) IN_C, or IN_D or both, then /FAULT pin goes low again.

Best regards,

Théo

Hi Theo

can the input side change it as below?

it seems different with our schematic.

thks

jess

Hi Jesse,

This is indeed solving one part of the problem! Thank you.

Adding the cap on INPUT_C & INPUT_D remove the /FAULT state. 
I must admit that the datasheet is tricky since they don't specify this in PBTL mode:

Ok, so the TPA3255 is now reacting normally to start up + RESET button.

However, there is still no PWM working even though IN_A & IN_B are receiving a signal (sinus) at the entrance.

I also tried to increase the gain of the AOP so that G is now 3 instead of 1; but this doesn't solve my problem here.

Best regards,

Théo

Hi Théo.

Théo Mnbs said:

Adding the cap on INPUT_C & INPUT_D remove the /FAULT state. 

Do you mean you float the INC and IND?

The schematic in our datasheet should be okay.

And when use PBTL mode, INC and IND should be connect to GND.

Please help to double check the M1 and M2 pin in your circuit is right.(M1 should be 0 and M2 should be 1). when I change the M1 to 1 and M2 to 0 in the EVM board, it report FAULT too, and when I remove the jumper which connect INC and IND to GND, the FAULT disappeared. This phenomenon is the same as yours.

BR.

Wei Qiu.

Hello Wei & Jesse,

Wei Qiu said:

Do you mean you float the INC and IND?

No, I was following this schematic, meaning I was shorting INC & IND directly to GND; but this is not working like this. Like the evalboard and what Jesse suggested above, it is important to add a 10uF capa.

With this 'upgrade', TPA3255 is reacting normally. /FAULT & /CLIP are high in PBTL mode. 

Wei Qiu said:

Please help to double check the M1 and M2 pin in your circuit is right.(M1 should be 0 and M2 should be 1)

Yes I confirm it's the case. As explained earlier, this was just a mistake I made on the schematic. This is already corrected.

The last concern I have now is that TPA3255 is not generating any PWM. With an audio sinus input, I see that TPA3255 is getting a correct signal at the entrance on IN_A & IN_B. CLIP is sometimes blinking (not continuously) ; showing that the audio clips sometimes. So the entrance stage seems to work fine.

What could explain that TPA3255 is not responding at the output ? Outputs are not grounded and PWM_A = PWM_B = OUT_A = OUT_B = 7,9V.

Best regards,

Théo

Hi Théo.

About this case, could I confirm something with you.

1. Do you mean if you don't connect 10uF to INC and IND will cause Fault? like below figure. 

Théo Mnbs said:

With this 'upgrade', TPA3255 is reacting normally. /FAULT & /CLIP are high in PBTL mode. 

Under condition A, it will not report fault. And under B condition, it will continue fault, right?

If so, it may cause by wrong PBTL connect.

If connect C and D directly to GND, this is the standard PBTL connection. But if you through a Cap to GND, internal bias will build through the caps.

So you can remove all inductors and check if the AMP can output PWM under this condition.

If possible, could you remove C23 and C34 to have another test?(directly connect input C and D pin to GND)

2. Does your side have a EVM board? If it can reproduce on our EVM board can help us to understand your question. My side can't reproduce your problem.

BR.

Wei Qiu.

Hello Wei Qiu,

Let me check again this and come back to you.

No I don't have any EVM board to test unfortunately.

Regards,

Théo

hi theo

you can apply EVM from this link.

https://tisamples.ti.com/order/tisamples/zh/%3f

tks

jess

Hello Jesse,

The link is not working. However, using https://tisamples.ti.com/order/tisamples/zh I could look for samples but TPA3255EVM is not available.

Only TPA3255 components that I already have.

Are you saying it is possible to request a sample for TPA3255EVM ?

Regards,

Théo

Hello Theo,

The provided link is mainly for internal use, we would recommend purchasing an EVM from the TI store or a distributor here at the bottom of the page https://www.ti.com/tool/TPA3255EVM.

best regards,
Luis