TPS54326: Funny behavior on VREG5

Brian Antheunisse

Part Number: TPS54326

Hi Team,

I have a customer using the TPS54326 and is having trouble:

"We got our new board but have troubles using the TPS54326 to generate +5.3A. I extracted our schematic and pasted below.

We isolated TPS54326 from input by removing an inductor(not shown in the below image) and fed +15VS from external power supply at TP98. L32 is also removed to isolated TPS54326 output. We added 100ohms between +5.3VA to GND to be the load.

At first power on TPS54326 its VREG5(pin3) reaches +5.5V. Then, drops to 1V(The 2nd board drops to 0V) after a couple of minutes. It never goes back to normal(+5.5V) even power cycle. The data sheet doesn’t have details of VREG5. What could be the reasons to cause this kind of VREG5 behavior?"

Thanks,

Brian

over 7 years ago

0 Gavin Wang (Zejing) over 7 years ago

TI__Expert 3480 points

Pls help probe Vin, VCC , VREG5, SW1 together.

0 Vental Mao over 7 years ago

TI__Expert 5745 points

By the way, pls upload your layout

0 Anthony Lang over 7 years ago

TI__Expert 4875 points

Hi Brian,

Is the output voltage also drops with VREG5? Could you show more information about other signals before and after VREG5 drops?

0 Brian Antheunisse over 7 years ago in reply to Anthony Lang

TI__Expert 5305 points

Hi Guys,

Well, my customer seems to have figured this one out on their own, but thank you for the collective response. If the issue pops back up I'll post again.

Thanks,

Brian

0 Anthony Lang over 7 years ago in reply to Brian Antheunisse

TI__Expert 4875 points

Hi Brian,

Just curious, what is the root cause for the low VREG5?

Power management

Power management forum

TPS54326: Funny behavior on VREG5