TPS61220: TPS61220 failed

Sneha Karthikeyan

Part Number: TPS61220

Tool/software:

Hi Team,

We’re using the TPS61220DCKR boost converter in our device, which is now in the production stage.

Recently, we received complaints about boost converter failures due to issues with the feedback resistors. Specifically, the output voltage of the boost converter unexpectedly increases to 5V or 4.4V instead of maintaining 3V. During the debugging process, we identified that the feedback resistors had failed, causing the output voltage to rise.

Could you please share your insights on the possible root cause of this failure?

Thanks!

11 months ago

0 Nini Zhong 11 months ago

TI__Genius 13715 points

Hi Sneha Karthikeyan,

did you try to start up open load. Can you help to provide some waveforms, indicating Vin, Vout SW and inductor current?

0 Sneha Karthikeyan 11 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

Do you need the waveforms of defective board?

0 Nini Zhong 11 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

Yes you are right!

0 Sneha Karthikeyan 11 months ago in reply to Nini Zhong

Prodigy 160 points

Sure. Will try and let you know!

0 Sneha Karthikeyan 10 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

Please find the schematics for the section.

Attaching the images of Vin, Vout, IL, SW in Ok board and Not Ok board for your reference.

IL of Not OK board:

IL of OK board:

Vin and Vout of Not OK board:

Vin and Vout of OK board:

SW of Not OK board:

SW of Not OK board - Zoomed:

SW of OK board:

SW of OK board - Zoomed:

Kindly do the needful.

Thanks!

0 Nini Zhong 10 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

Hi Snela,

I highly doubt that the feedback resistor is wrongly placed for the fail part . Could you double check with it, because the Vout is about 6V, much higher than max ratings. Also for SW waveform, did you utilize the offset? Because I saw the negative voltage , which is abnormal.

0 Sneha Karthikeyan 10 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

Thanks for your response.

The device operates normally for the first few months, and the complaints regarding the boost converter failure started only after this period. This indicates that the correct resistor was populated initially, as it functioned properly for a while before failing.

We’ve observed the IL waveform behavior:

On the failure board, the IL waveform starts at 0V (during power off) and rises to 68mA during power-up.
On the working board, it starts at 0V (during power off) and stabilizes at 13mA during power-up.

Kindly share your insights regarding this observation and help us identify the root cause of the issue.

Additionally, we probed the R6 (604k, 0.1% tolerance) resistor values across 10 working boards and found the following:
206k, 205k, 205k, 201.9k, 205.5k, 203.9k, 199.7k, 206.2k, 200.3k, 201.6k.
Why are these values inconsistent?

We also probed the inductor value with a multimeter on the failed board and observed it as overload.

Looking forward to your feedback.

NOT OK Board IL waveform:

OK Board IL waveform:

Also having another doubt,

What is the relation between above two images? How to calculate IFB?

Thanks!

0 Nini Zhong 10 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

1. the resistance has variation and it's normal phenomenon .

2. Could you observe the whole picture of inductor current , such as 2ms scale ?

3. The Ifb is quiescent current from FB pin, it depends on the device it self. You don't need to calculate it.

0 Sneha Karthikeyan 10 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

Please find the attached image for your reference.

IL - Ok board:

IL - Not Ok board:

Thanks!

0 Nini Zhong 10 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

Hi I don't think the load is the same. Could you double check with that ?

0 Sneha Karthikeyan 10 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

The image we sent earlier was probed using a multimeter. Now, we have probed it using an oscilloscope with a sampling frequency of 1 GHz.

Both are the waveforms of the same boards.

Thanks!

0 Nini Zhong 10 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

Now I am a little confused. Could you ship me the two pieces to test?

0 Sneha Karthikeyan 10 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

Sure, we'll ship the boards. Kindly share the shipping address.

0 Nini Zhong 10 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

I will send through private message. Just warmly close this thread

0 Sneha Karthikeyan 10 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

We have shipped the boards, and the tracking number has been shared with you via a private message.

Kindly check and proceed with the evaluation.

0 Nini Zhong 10 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

Okay

0 Sneha Karthikeyan 9 months ago in reply to Nini Zhong

Prodigy 160 points

Hi Nini,

Did u receive the boards?

0 Travis Wang 9 months ago in reply to Sneha Karthikeyan

TI__Expert 8895 points

Hi Sneha,

Expert for this device is out of office. Please expect a delayed reply.

Best Regards,

Travis

0 Sneha Karthikeyan 9 months ago in reply to Travis Wang

Prodigy 160 points

Hi Travis,

Thanks for the reply.

When will we expect the reply from your side?

Thanks!

0 Nini Zhong 9 months ago in reply to Sneha Karthikeyan

TI__Genius 13715 points

Hi Sneha,

To be frank, I haven't received the board because the custom department requires special proof before I get the package. Last week I just provided the information and hopefully it is to be delivered by the end of this week.