LM5085: Current output LM5085

User,

The schematic looks good. What prevents the full load output? Does the output voltage drop? Please describe what is happening.

Please also share the layout and part numbers for L01, D01, and M0.

Thanks,
-Sam

Ok, right.

I have a pcb that only use this part:

The part numbers for L01, D01, and M0.

     L01--> IHLP6767DZER330M11

     D01--> MBRB40250TG

     M0--> ZXMP10A18KTC

The output voltage drop when i have a little Rl, for example, when i have a Rl=10ohm and i have a 50V input i have a correct output but if i have a smaller Rl=4ohm (for the output 12V and 3A) the voltage output is 9V.

User,

I missed something on the schematic. I see there is an output capacitor labeled CFF. If this is supposed to be a feed-forward cap then it needs to be connected in parallel with Rfb2, not from VOUT to GND.

The layout can also be improved. You can find layout recommendations in the datasheet. Perhaps most importantly try to keep high di/dt loops small. Trace the path from the CIN caps through the circuit and back to the CIN cap. This loop should have a smaller area.

-Sam

it,s true! the cff capacitor is a gnd, but if i have cff in parallel with the Rb2 the circuit have the same behavior.

User,

In that case I recommend reworking the layout. Layout is often the cause of issues like this - the circuit works for some cases but not all.

-Sam

Ok,

I made other PCB with the same paramenters and the schematic correction, but i have the same problem when i have a RL that the current is over the 2.2A, the output of LM5085 it's not operative.

User,

You will most likely need to create a new board with a new layout to get this to work.

-Sam