TPA3220EVM-MICRO: CLIP_OTW LED flickering and output switching "on/off"

Christian Funck

Part Number: TPA3220EVM-MICRO
Other Parts Discussed in Thread: TPA3220

Hi,

I am having issues with the TPA3220 EVM MICRO. I set everything up according to the quick start instructions in the user guide, using 5 ohm resistors as a load. Connecting a signal at 1kHz with amplitude (10mV ... 150mV), I get the following behavior:

CLIP_OTW LED is flickering (increases with input amplitude).
Measuring (differentially) the output voltage across the load, I see that the output is switched of every 2 ms for 1.5 ms or so. A screenshot of the scope is attached.
even when setting the input amplitude to 0, I observe this 'switching'. But no LED flickering. (second screenshot)

Is the device broken, or what could be the reason for this strange behavior?

Thank you very much for any help.

Best regards,

Chris

No input signal:

over 5 years ago

0 Shawn Zheng over 5 years ago

TI__Mastermind 24835 points

Hi Christian,
Looks like fault is triggered. Are you using it in mono mode or stereo mode? If mono mode, please make sure PBTL mode is enabled.
Best regards,
Shawn Zheng

0 Christian Funck over 5 years ago in reply to Shawn Zheng

Prodigy 60 points

Hi Shawn,

Thanks for your reply.

The FAULT LED stays off, however. (It blinks once when I flip the reset switch and then stays off, but that seems to be the desired behavior?). But the CLIP_OTW LED keeps flickering... I am using the standard stereo BTL mode (I did no modifications on the board).

Any suggestions are greatly appreciated.

Thanks,

Chris

0 Robert Clifton56 over 5 years ago in reply to Christian Funck

TI__Mastermind 20780 points

Hi Chris,

Do you see the CLIP_OTW flicker with no signal going through the device? Is there any other weird behavior that's happening with no signal going through the device?

Regards,

Robert Clifton

0 Christian Funck over 5 years ago in reply to Robert Clifton56

Prodigy 60 points

Hi Robert,

There is no flickering of the CLIP_OTW when no signal is applied. The flickering stops mostly when the input amplitude is <50mV, but the output behavior stays as before.

When there is no signal applied, there is no flickering of the LED, but the output still shows the strange behavior as in the second screen shot of the original post, i.e. there is still some kind of switching going on...

Thanks and best regards,
Chris

0 Robert Clifton56 over 5 years ago in reply to Christian Funck

TI__Mastermind 20780 points

Hi Christian,

Can you please look of the output of the 5V power supply. R14 and R18 would be good points to put the probe on.

Thanks,
Robert Clifton

0 Christian Funck over 5 years ago in reply to Robert Clifton56

Prodigy 60 points

Hi Robert,

the voltage is around 5.14V, and stable (with some HF noise on it), both with input signal applied or no input signal.

Thanks a lot for the support so far.

Best,

Chris

0 Robert Clifton56 over 5 years ago in reply to Christian Funck

TI__Mastermind 20780 points

Hi Chris,

Ok since the power supplies appear to be stable that leaves the most likely scenarios to be:
- Thermal issues
- Contact problems

Thermal issues seems like the less likely since the Fault Light LED never went off.

Contact problems could be a number of things. Can you verify that there is a solid connection from the board to the resistor? Also can you verify that the cable you are using can handle the current that you are delivering to the resistors?

0 Christian Funck over 5 years ago in reply to Robert Clifton56

Prodigy 60 points

Hi Robert,

Basically I connect the resistors directly on to the board. I also measured the input voltage at R15/17 and R21/24 with the scope and it is ok.

Under what circumstances is the OTW_CLIP LED actually activated?

Could the amplifier IC be damaged?

Thanks again and best regards,

Chris

0 Robert Clifton56 over 5 years ago in reply to Christian Funck

TI__Mastermind 20780 points

Hi Chris,

Usually the OTW_CLIP LED will be active when either the device is at about 125C or the device is severally clipping. However you can tell the difference whether it is clipping or OTW. If the device is clipping the LED would appear to be dimmer compared to an OTW event where the LED is at max brightness. This is due to clipping event only occurring during the peaks of the output signal causing a PWM signal coming out of the OTW_CLIP LED.

I can't say that the amplifier IC is damaged without getting it in person to verify. Do you have another EVM board? If it's also behaving the same way that would indicate that it could be the setup that's causing issues.

Regards,

Robert Clifton

0 Christian Funck over 5 years ago in reply to Robert Clifton56

Prodigy 60 points

Hi Robert,

Thanks for the support. Unfortunately I do not have a second board. I will send the board back to the supplier.

I will let you know what the result is.

Thanks again and best regards,

Chris

0 Shawn Zheng over 5 years ago in reply to Christian Funck

TI__Mastermind 24835 points

Hi Chris,
I'm closing this question, please feel free to create a new post if you have any other question.
Best regards,
Shawn Zheng

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TPA3220EVM-MICRO: CLIP_OTW LED flickering and output switching "on/off"