LM25148: Over current protection range

lei wang

Part Number: LM25148

Hi,

We use the over current protection function of the LM25148 controller. But it doesn't work well, like the current trip range is pretty wide.

For example, the output voltage drops at 3.5A and the system totally shuts down at 4.3A. The chopping frequency is set at 500KHz.

Any ideas will be helpful.

Thanks,

0 Orlando Murray over 2 years ago

Hi Lei,

What does your schematic and layout look like? Did you route the current sense signals internally and away from noise sources?

Are you able to add a current sense filter?

Reference the EVM:

Let me know,

-Orlando

0 lei wang over 2 years ago in reply to Orlando Murray

0 Orlando Murray over 2 years ago in reply to lei wang

Lei,

10mΩ current sense resistor sets a peak inductor current limit of 6A.

What current do you need?

Do you have a quickstart calculator?

Please fill this out with your spec.

-Orlando

0 lei wang over 2 years ago in reply to Orlando Murray

Hi Orlando,

The desired current limit is 4A. I did use the LM25148-Quickstart-Calculator_rev3. Please check the attachment. LM25148-Quickstart-Calculator_rev3-24V.xlsm

0 Orlando Murray over 2 years ago in reply to lei wang

Hi Lei,

Got it, the design looks OK.

You can try increasing the amount of your current sense differential mode filtering, you can increase R10 to 100Ω and C30 to 270pF.

This will help filter any DM noise that couples onto the current sense signal.

Otherwise, a small capacitor from VOUT to GND close the VOUT pin can help with common mode noise.

Hope this helps,

-Orlando

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