TPS55340EVM-017: Followed schematic for PCB . output is 30V instead of 24V

Stefano Alfredo La Spina

Part Number: TPS55340EVM-017

Hi. I have realized a standalone power supply following TPS55340EVM-017, 5-V to 12-V Input, 24-V Output Boost Evaluation Module.

After PCB arrived the output is fixed to 30V, not 24.

Have checked all components, also formula that calculates resistance value of feedback obtaining a value of 185k rounded to 187k value.

The problem is I have 30V output value.

with all load conditions,

any help? What should I consider next?

Best regards and thanks

Stefano

over 2 years ago

+1 Niklas Schwarz over 2 years ago

TI__Mastermind 30140 points

Hi Stefano,

Thanks for using the e2e forum.

If the output stays fixed at 30V, might first suggestion would also be to check the feedback divider. Them EVM uses a feedback divider of 187k (upper resistor) and 10k (lower resistor) to meet the reference voltage of 1.229V.
Have you tried to change the resistors to another value to see the output voltage does not change at all?

Can you also share a schematic of your circuit, so I can check from my side as well if there is anything missing?

Best regards,
Niklas

0 Stefano Alfredo La Spina over 2 years ago in reply to Niklas Schwarz

Prodigy 240 points

Thanks Niklas. Sure, here it is attached. So first point should to measure ref voltage of 1.229V at FB pin8 right? Changing resistor value is a little bit tricky since I used the 0201 resistors but will try. Thanks alot. Regards

0 Stefano Alfredo La Spina over 2 years ago in reply to Stefano Alfredo La Spina

Prodigy 240 points

Niklas, found the culprit... just a three orders of magnitude error... FBloop resistor was 49k instead of 50ohm...OOPS. Thanks again.

0 Niklas Schwarz over 2 years ago in reply to Stefano Alfredo La Spina

TI__Mastermind 30140 points

Hi Stefano,

Thanks for the update.
I am glad to hear you were able to find the source of the error

Best regards,
Niklas

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TPS55340EVM-017: Followed schematic for PCB . output is 30V instead of 24V