TPS551892-Q1: Switches off and Short circuited after few mins :URGENT

Pragadheeswaran Venkat

Part Number: TPS551892-Q1

Tool/software:

Please refer my attached application circuit . I used TPS551892QWRYQRQ1 to convert (14V to 24V ) input supply to requlated output of 12V / 2Amps max current output . VCC used as internal .

After assembly i switched ON obsorbed 12.13V at the output . continionus ON , voltage output stable and NO load connected . Few mins ( <2mins) after output become Zero and no observation of heat the requaltor o/p continue to be zero . I tried to chage to the external VCC the chip input rail short circuited . i replaced 3 chips all behave very similer after few mins ( less 2 mins ) it becomes zero and eventually short circuiting in VIN line ( 7th pin ) . One chip i connected 200mA light load same ON the load perfectely works with 12.12 volts and same happened after few mins . I attached the schema . Please advice what went wrong .

6 months ago

0 Mulin Yuan 6 months ago

TI__Genius 15250 points

Hi,

Thank you for reaching out. Please help provide more details for me to check:

1. Can you provide FB2 part number? Is it 220ohm/4A? Did you try to remove this FB?

2.What is rated voltage of C26?

3.What is saturation current of L2?

4. Can you provide output cap part number for me to check the compensation parameters?

5.Can you provide layout for me to check the design?

6.Can you capture SW1, SW2, Vout, inductor current waveforms? It will be better if you can capture the damage moment.

Regards,

Mulin

0 Pragadheeswaran Venkat 6 months ago in reply to Mulin Yuan

Prodigy 95 points

Hi,

Below you can find responses to the questions you've asked:

1. PartNum of FB2 - 120E, 3A used

2. C26 rated voltage is 50V

3. Saturation current of L2 is 17A, DCR max is 16.50

4. PartNum of output caps:

4a. C29 - CC0805KKX7R9BB105

4b. C30 - GRM21BR61H106KE43L

4c. C31 - 10mm, 50V

5. I'm attaching snippet of gerber data for your reference.

6. We haven't done that. Will try to get that and post it in the thread.

0 Mulin Yuan 6 months ago in reply to Pragadheeswaran Venkat

TI__Genius 15250 points

Hi,

It is very obvious that layout is the root cause. For the buck-boost, there will be large current flowing VIN, VOUT, SW1, SW2, GND. So wide trace and polygon is needed for thermal dissipation and reduce parasitic parameters. Current design will cause terrible thermal performance and huge parasitic parameters, causing large spikes. Please refer to the layout guideline and re-design the layout.0882.TPS55289 Layout Guideline.pdf

Regards,

Mulin

0 Pragadheeswaran Venkat 6 months ago in reply to Mulin Yuan

Prodigy 95 points

Hi,
Thank you for your response. We will consider this layout guidelines and update our PCB. I'll post the update once the PCB is ready, until then pls don't close this thread.

0 Mulin Yuan 6 months ago in reply to Pragadheeswaran Venkat

TI__Genius 15250 points

Hi,

Feel free to reply to this thread. I will wait for your update.

Regards,

Mulin

0 Pragadheeswaran Venkat 6 months ago in reply to Mulin Yuan

Prodigy 95 points

Hi,

Can I have the eval board design files(Altium) for reference. Also is it possible to go for 2 layer PCB with the design.

0 Mulin Yuan 6 months ago in reply to Pragadheeswaran Venkat

TI__Genius 15250 points

Hi,

Please send me a friendship request and I will send you the file by message. We only have 4 layer file. If your PCB is 2 layer, please pay more attention to thermal dissipation design.

Regards,

Mulin

0 Pragadheeswaran Venkat 6 months ago in reply to Mulin Yuan

Prodigy 95 points

Hi,

I've send you friendship request. Kindly check.

0 Mulin Yuan 6 months ago in reply to Pragadheeswaran Venkat

TI__Genius 15250 points

Hi,

Sure~ I will send to you.

0 Pragadheeswaran Venkat 6 months ago in reply to Mulin Yuan

Prodigy 95 points

Received the file. Thanks!

0 Mulin Yuan 6 months ago in reply to Pragadheeswaran Venkat

TI__Genius 15250 points

Hi Venkat,

Please keep this thread quiet before you modify the design and then feel free to send to me to review. Thanks!

Regards,

Mulin

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TPS551892-Q1: Switches off and Short circuited after few mins :URGENT