How to limit the out current using the MP4575

DC-DC Power Converters
1

Hi,
We need to have the MP4575 limiting the output current to -say- 3A.
Not sure how to use the COMP input.
Could you provide a schematic on this purpose ?
Appreciate,
Jerome

2

Internet weirdo here. This is a peak current mode controller with a gm amplifier. So the voltage at the Comp pin = peak inductor current and is a pretty good proxy for the output current. So clamping the voltage will result in a kind of current limit. Try two diodes in series comp to ground to clamp the voltage at 1.4V and see what happens. The questions come when “how accurate do you need to be” how much unit to unit variation is allowed? I don’t see anywhere on the datasheet where they specify the Vcomp to I pk relationship. the next level would be to put a current sense amplifer in the circuit to measure the current and tug down on the comp pin in the event that the setpoint was exceeded.

1 Like
3

Thanks a lot for your suggestions, will let you know how this will end. Sorry for my late reply. I think Monolithic could respond, too. Jerome :slight_smile:

4

Thank you, John, for helping Jerome!

Jerome,
Thank you for utilizing MPS Technical Forum,

Output current can be limited via comp pin, as you have identified, you may use DCDC designer tool for this device to size the COMP network.

DC DC Designer Online - Design Tools - Design (monolithicpower.com)

Best Regards,
Nouman

5

Thank you, Nouman.
I’ve been to this designer and it is really helpful.

Another topic : the designer and the tool on the product page do NOT give the same value for the inductor, within a vast range (on the product page, the calculation gives about 7uH when the designer calculates 33uH ! For 3A).

Can you advise why MPS provides those so different values ? (i can provide the screen captures)

Thank you,
Jerome