LM5141-Q1: The circuit won't supply current higher than 0.8A if configured to 5V

Michael Fraimovich

Part Number: LM5141-Q1
Other Parts Discussed in Thread: LM5141

Hi there,

We are having an odd issue with LM5141-Q1.

On our custom board we have designed two supplies (3.3V and 5V) using the same IC. The two circuits designed based on Webench and verified against the datasheet. The layout designed with accordance to the datasheet guidance and suggested layout.

The 3.3V worked right away, tested up to 2A load. But the 5V circuit can only supply current not higher than 0.7-0.8A, than it shuts off (goes down to 0V)

When we configured the working 3.3V circuit to 5V it behaved similarly, was only capable of 5V/0.8A max.

We have tried playing with the input and output capacitors, adding ceramic caps of various values (0.1uF - 39uF). Played with the compensation as well. Bottom line: 5V won't do any better then 0.8A.

Attached the schematics. I will be happy to get any help: suggestions, design and layout review and etc... Thanks.

LM5141-Q1_Power issue.pdf

over 7 years ago

0 David Baba over 7 years ago

TI__Mastermind 40040 points

Hello Michael,

Please can you provide details of the layout?

Also Can you take scope captures of the switch node before the 5V supply shuts down. Would like to check if the Switch node is stable?

Thanks.

David.

0 Terry Allinder over 7 years ago in reply to David Baba

TI__Expert 3545 points

Michael,

What is your Vin operating range? I reviewed your schematic the component selection seems ok. I would decreases C222 and C239 to around 47pF, but I don’t think that’s the problem. Have you looked at the RES pin to see if the LM5141 is in Hiccup mode, it may think there’s an overload condition?

As David mentioned we would like to take a look at the PCB layout.

Terry

0 Michael Fraimovich over 7 years ago in reply to David Baba

Prodigy 170 points

Hi David,

Thanks for the fast reply. Can I please get your email? This design is under a NDA with the customer and I will be in troubles if shared it here. In general though the working layout of 3.3V supply is 99% similar to the troublesome 5V supply.

Thanks!

0 Michael Fraimovich over 7 years ago in reply to Terry Allinder

Prodigy 170 points

Hi Terry, the Vin is 10-24V. Thanks for the idea, will check the waveform on Tuesday and post it here. The layout must go through the email s though.

0 Terry Allinder over 7 years ago in reply to Michael Fraimovich

TI__Expert 3545 points

Michael,

My work email is terry.allinder@ti.com.

Terry

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LM5141-Q1: The circuit won't supply current higher than 0.8A if configured to 5V