LM61495: LM61495 get short, SW and VIN is getting short.

Muhammad Usman Rafique

Part Number: LM61495

Tool/software:

I used the WEBBENCH designer to design a buck converter that converts 24V to 15V. I used the PSpice for TI to simulate and it showed correct behaviour (image attached). Now I have designed my PCB. When I was testing, IC get shorted whenever I connected the input and during troubleshooting I removed the output capacitor and it was giving me the output of 17V after inductor which was also strange because at fb pin it was giving 1.22V but now whenever I place the output capacitor and solder it, the circuit get short. No smokes comes out but the circuit stops working. So when I test IC after removing the SW pin and VIN pins are short.

My components are the same which was suggested by WEBBENCH designer. The little difference is that I have soldered only two capacitor (10uF) on PCB at (GRM32ER71H106KA12L) instead of 4.

Best Regards,
Usman

3 months ago

0 Andrew Kutzler 3 months ago

TI__Mastermind 23795 points

Hi Usman,

I will check with the team if it's ok.

Thanks,

Andrew

0 Andrew Kutzler 3 months ago in reply to Andrew Kutzler

TI__Mastermind 23795 points

Hi Usman,

I'm looking at the layout and it seems like VIN is very close to SW? Are the shorted in operation? How many failures do you have?

Thanks,

Andrew

0 Muhammad Usman Rafique 3 months ago in reply to Andrew Kutzler

Prodigy 10 points

They are shorted during operation. I have figured out the problem, I was working with 3.3V version, the LM61495Q3RPHRQ1 instead LM61495QRPHRQ1. Do you suggest should I not used this closed track for VIN and SW? should I leave VIN upto pin13 and 14 ? as pin 14 and 2 is already connected inside the IC.

Sorry for my newbie mistake for ordering the wrong version.

0 Andrew Kutzler 3 months ago in reply to Muhammad Usman Rafique

TI__Mastermind 23795 points

Hi Muhammad,

It's ok. I would still recommend delivering VIN through a different layer using a via. As you can see the VIN may pick up some noise from the SW node because the trace gets quite close to SW.

Thanks,
Andrew

Power management

Power management forum

LM61495: LM61495 get short, SW and VIN is getting short.