I am planning to use a Diodes AP5100 switching regulator to go from ~22V to 12V in my circuit, which will have a max current draw of about 1A. This is my first attempt at laying out a switching power supply and I tried to follow the recommendations (double quoted below) in the datasheet as closely as possible.
"The input capacitor needs to be as close as possible to the IN and GND pins."
- I put C1 close to IN pin 5. Should I try to get C1 closer to the ground pin 2?
"The external feedback resistors should be placed next to the FB pin."
- R1 & R2 feedback resistors are near FB pin 3. I could move it closer if needed.
"These interconnecting impedances should be minimized by using wide, short printed circuit traces."
- I believe that was accomplished.
I am not sure if it's a good idea to route R2's ground connection under the IC to ground pin 2? Maybe using a via directly to the ground plane is better?
Also, I am not sure if the ground island for minimizing ground bounce is laid out correctly or is even is necessary. It actually might be makings things worse in terms of EMI.
I think the inductor that I am planning to use might be too small. It's current rating is only 1.6A.
Please offer any advice on how to improve the layout or anything else.
Thanks to everybody for all of the suggestions and I made the following changes:
- removed the ground island
- moved L1 closer to pin 6
- feedback measured directly off C2 now
- added double vias to the ground plane for C1, D1 and C2
- added a second GND connection
- should pin2's ground connection be made with a double via also?