NB679 output voltage fall

Hi. I made a device using NB679. Scheme from a datasheet. VIN = 12V, R_UP = R_DOWN = 1MOM. VOUT = 5V no load. With a load, at a current of 1A, the voltage drops to 4.2 (another instance 3.15). What could be the problem?

Hi lvasa3091,

There are a number of reasons the output can droop, including output capacitance (too little or too much), instability from component choice, inductor ratings, and possibly layout issues. My suggestion is to follow the 5V output reference design from the evaluation board and reference design layout from the datasheet for the NB679 as closely as possible.

Thanks,
Brendan Schoemehl
Field Applications Engineer
Monolithic Power Systems | MPS Now

Thank you. I will experiment more.