LM22676: Output voltage has a large ripple when it works at light load condition

user5990201

Part Number: LM22676

As shown in the figure above, I use DAC_FB_VEF1 to adjust output voltage of LM22676.

At most of the time, it works good. But when the ouput current is very low especially when it's lower than 30mA, the output volatge has a quite large ripple, which is about 2.5V, with a period 50~400ms(input voltage is 28V, output voltage is 22V). And it could hiccup repeatedly.

Could you help me with this problem?

Thank you.

over 4 years ago

0 Samuel Jaffe over 4 years ago

TI__Mastermind 25590 points

User,

I don't see any input capacitance. You will need to add input capacitance to allow proper operation.

If you have sufficient input capacitance, you may need to increase your inductor closer to the datasheet calculated 31uH (eq 12).

-Sam

0 user5990201 over 4 years ago in reply to Samuel Jaffe

Prodigy 190 points

There is another problem about this device. When the load current is 3A, the temperature of this device is nearly 100 centigrade. What do you think of this problem?

By the way, If the problem can not be solved, I'd like to find another device to replace it.

I'd like this replacement device 40V/3A, and it have Pin to Pin solutions with 48V/3A, or 40V/5A, or even 48V/5A。

Could you recommend a device for me?

Thank you.

0 Samuel Jaffe over 4 years ago in reply to user5990201

TI__Mastermind 25590 points

User,

How are you running this at 3A? You have a 1A fuse. Plus your inductor is rated for 2.2A. You may need to find an inductor with a higher current rating.

We do not have any pin to pin replacements with those specs.

-Sam

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LM22676: Output voltage has a large ripple when it works at light load condition