TPS55289: Abnormality at startup

Hi Shumpei,

Thanks for reaching out. 

1. May I know what is the application and product type here?

2. Can you show your schematic and layout here?

3. Can you add the wire in series with the inductor and probe the inductor current? 

And please zoom in the waveforms to 2us/div including SW1, SW2, iL and Vout in the below marked rectangle.

BRs,

Bryce

Hi Bryce,

I use it for VBUS of Type-C PD (5~20V out).

I will sent schematic and layout by email.

Please tell me the email address.

The desired waveform is below.

Thank you.

Hi Shumpei,

Please send the files to my email bryce-xun@ti.com

Can you show the register value of the TPS55289 at the startup period?

BRs,

Bryce

Hi Bryce,

I sent email.

Best Regards,

Shumpei

Hi Shumpei,

I have received the email.

First, since the output capacitors are small, the current compensation parameter is not good, recommend to change R9608 to 2.5k, C9614 to 6.8nF.

Secondly, the layout is poor with switching regulators, for example, the crossed connection is not recommended for GND connection. And the input, output capacitors are far away from Vin, Vout pins. The VCC trace is thin.

It is recommended that you can modify the comp parameters and retest again.

BRs,

Bryce

Hi Bryce,

Thank you for confirming.

I modified comp parameter, but it didn't seem to improve.

I was using TPS552892 with similar peripheral parts and layout for another purpose.

I tried replacing it with TPS552892, but it didn't happen startup error.

For example, will it improve if I set TPS55289's FB to external?

Best Regards,

Shumpei

Hi Shumpei,

Do you mean you replace TPS55289 with TPS552892 on the same board, and the startup is normal now?

If so, I am wondering if you change the internal ref values during the startup period(4ms)?

BRs,

Bryce

Hi Bryce,

Yes. I replaced as shown below.

Block contains each capacitor, inductor, shunt resistance, and peripheral parts.

Best Regards,

Shumpei

Hi Shumpei,

Since it has two weeks from your last update, may I know if the issue is solved?

Best regards,

Bryce Xun

Hi Shunpei,

We have not seen an update from you for three weeks, so I assume the questions are answered and the issue is solved.

I close this thread now. If there is still something open, please reply and the thread will get opened again.

If you have any other question or of the thread has been locked, please open a new one.

Clicking the Resolved Button also helps us to maintain this forum.

Best regards,

Bryce