MP2451 5v to 3.3V


First of all, I want to state that I’m quite new to power converters design, so I apologize for any obvious mistakes.
I want to convert a 5V input source to 3.3V, and the MP2451 part was available in the catalog I’m looking. Reading through the datasheet, I found that it states it can do up to 0.8x Vin (=4V, or 3.6V if we allow 10% margin for the input), which fits. However, reading on, in the section about the bootstrap diode (page 12), it says it’s recommended for Vout/Vin > 0.65, which is the case. However, the bootstrap diode section also states that in this case, Vin must be at least Vout + 3V, which is not possible for my application. It also states some things about UVLO and programming throuhg the EN pin, but I’m not sure if I understand it.

What I want to know is: is it possible to use this chip to convert from 5V to 3.3V? If so, should I use the external bootstrap diode?
Again, I’m new to this kind of thing, and therefore please forgive any mistakes or lack of understanding from my part.


Best regards,

Why? MPS makes dozens of chips specifically for 5 to 3.3. What is it about this one that is so attractive? How about the MP2158A?.

The problem they have with this part is establishing sufficient voltage on the bootstrap cap to cleanly switch on the internal MOS. Which is where likely the Vin must be higher than Vout by 3V. A synchronous chip, where the external freewheeling diode is replaced by an internal MOS is more efficient and smaller ( no diode) and thanks to the internal MOS can establish sufficient voltage on the bootstrap cap at startup.

A further warning sign is none of the datasheet circuits show 5 to 3.3, I used to do application engineering and one thing was you did always try to show the maximum capability of whatever chip you were featuring. You have better choices than this chip, don’t push on a rope.

Hello jshannon,

Thank you for the answer. Actually, I have no specific reason to use this chip, it just was on the inventory in convenient quantities. I’ll look if there are better suited parts for the application.

Hi laezbffilho,

Welcome to the MPS Technical Forum! Yes, it is possible to use the MP2451 for your application. I’m assuming your Iout is below/at the 0.6A rating. What is your output current spec? You are correct that bootstrap diode would require a larger difference between your input/output voltage, so I would not recommend you include it.

I agree with jshannon that this device might not be the best suited for your application. Depending on your output current, I recommend looking at other devices like the MP2172, MP2122A, and the MP2172C as these are better suited for your voltage range.