TPS2373-4EVM-758: Zener Diode Getting Hot

Mike Oudshoorn

Tool/software:

Dear TI,

I'm having some issues with a DC-DC converter design. I used the reference sheet to make my schematic. The dc-dc converter works and is outputting 5v. But a zener diode (D5) is getting very hot (200C) and burning up.

I'm measured the voltage on both the resistor (R73) and transistor emitter (Q8). Respectively 0,5V@1mA and 4,7V.

Could you please help me figure out how to fix this issue.

Kind regards,

Mike

Hubbay-PoE PD.pdf

11 months ago

0 Diang Xing 11 months ago

TI__Mastermind 37121 points

Hi Mike,

Thanks for reaching out! Sorry that PoE team is quite busy recently. I will try to get back to you in 4 business days.

Best regards,

Diang

0 Diang Xing 11 months ago in reply to Diang Xing

TI__Mastermind 37121 points

Hi Mike,

Thanks for your patience. I did not find gate drive circuit has an issue. May be you can double check the value of R73 and C100 and make sure their values are correct? C100 could be not mounted for debugging.

Best regards,

Diang

0 Mike Oudshoorn 11 months ago in reply to Diang Xing

Prodigy 30 points

Dear Diang,

I measured the value of R73 which shows 507 Ohm and C100 is 470pF. In one of the boards the diode burned up and i hear a clicking noise.

Kind regards,

Mike

0 Diang Xing 11 months ago in reply to Mike Oudshoorn

TI__Mastermind 37121 points

Hi Mike,

Thanks for update. I will get back to you in 5 business days.

Best regards,

Diang

0 Diang Xing 11 months ago in reply to Diang Xing

TI__Mastermind 37121 points

Hi Mike,

Thanks for your patience.

Could you measure the FETs' Vds voltages? They should be like below picture but with different amplitude. Can you also measure the Q15's Vgs?

Best regards,

Diang

Power management

Power management forum

TPS2373-4EVM-758: Zener Diode Getting Hot