LM5085: The output is increasing when the load is on

user5811580

Intellectual 700 points

Part Number: LM5085

I just made a DC/DC module with LM5085.

The output is designed to be 12V.

In fact, the output is 12.10V when there is no load.

When the load is on , the output will be up to 12.5V.

When the load current is up to 3A, the output will be changed to 13V.

Besides, the output is stable.

Is it normal for LM5085?

over 6 years ago

0 Samuel Jaffe over 6 years ago

TI__Mastermind 25590 points

Wu Shi,

This is not normal. How are you measuring this? And can you please share the schematic and layout?

Thanks,
-Sam

0 user5811580 over 6 years ago in reply to Samuel Jaffe

Intellectual 700 points

Please check the schematic and the layout.

Besides, there is a whole gnd on the bottom side with respect to the layout.

I just measured VCC_MCU1_12V with a digital multimeter.

0 Samuel Jaffe over 5 years ago in reply to user5811580

TI__Mastermind 25590 points

Wu,

Where are you connecting the multimeter to measure the output voltage? The controller senses FB from a point close to C428 so you should be measuring from C428.

Try removing R424. This will change your ripple injection to a simple feed-forward cap. That may change things.

Does this incorrect VOUT change with VIN? For example if you increase VIN to 10% will your 13VOUT (at full load) increase by 10% as well?

-Sam

0 Samuel Jaffe over 5 years ago in reply to Samuel Jaffe

TI__Mastermind 25590 points

Wu,

I have not heard back from you. I will close this thread. Please respond or post again if you are still having issues.

Thanks,
-Sam

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LM5085: The output is increasing when the load is on