Resister at BST terminal_MP2333H


We see MP2333H need resister R4= 20 ohm page1 in the data sheet.

On the other hand , MP2321 does not need it in the data sheet.

Why there are difference?

Resister at BST can be zero instead of 20ohm in case MP2333H also?

Thank you and with best regards

Hi Kanji, welcome to the forum.

I believe the Rbst resistor is there to limit the inrush current into the Cbst capacitor as it charges. It’s good practice to put a placeholder resistor next to the Cbst, even if you plan to place a 0 Ohm resistor during your build.

That way, you can stuff a Rbst if you need to slow down the ramp as Cbst charges.

Dear Kareem-san,

Thank you for your answer so quickly.
I will suggest customer to use Rbst=22ohm to limit in-rush current
, Cbst=1uF for proper operation when duty is so low, and have a placeholder at least
for Rbst.

Thank you again