TPS54540: TPS54540 problem over 500mA

Gokhan Sahin

Prodigy 210 points

Part Number: TPS54540

Hi everyone,

I have designed a power control circuit with TPS54540, its input voltage range from 6.5-40V and output current 5A.

I reference the webench circuit to design.

I'm taking 5V when there is no load or supplies 500mA.

However, I have tried over 500mA, the output voltage decreases to around 800mV. (There are no parts which are getting overheating)

Where do I mistake? Please help me.

I enclosed the PCB and schematic.

Disabled the gnd polygon pours for top and bottom.

over 6 years ago

0 Orlando Murray over 6 years ago

TI__Mastermind 22301 points

Hi Gokhan,
The TPS54540 is not recommended for new designs.
I am reviewing your schematic now, but I believe that may be related to your load regulation issue.
Are you able to get a TPS54540B or a different IC?
-Orlando

0 Gokhan Sahin over 6 years ago in reply to Orlando Murray

Prodigy 210 points

For now I need this board but will update it new version later. Well how can I solve this problem?

0 Gokhan Sahin over 6 years ago in reply to Gokhan Sahin

Prodigy 210 points

Is the layout wrong? or the problem is caused by another thing?

0 Orlando Murray over 6 years ago in reply to Gokhan Sahin

TI__Mastermind 22301 points

Hi Gokhan,
The layout looks good and schematic look good, is the diode D3 a schottky diode?
What exact conditions does the output voltage drop? Is it across all VIN?
-Orlando

0 Gokhan Sahin over 6 years ago in reply to Orlando Murray

Prodigy 210 points

Orlando Murray said:
Hi Gokhan,
The layout looks good and schematic look good, is the diode D3 a schottky diode?
What exact conditions does the output voltage drop? Is it across all VIN?
-Orlando

Thanks a lot, Orlanda.

Since the D3 diode isn't a Schottky, the output voltage decreased.

After changed it, it works perfectly.

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TPS54540: TPS54540 problem over 500mA