I was getting ready to do a board layout with the TPS54325 and thought it wouldn't hurt to get some feedback on my part placement before I started the routing. I'll have a 12V input and actually 2 of these circuits in parallel, one to generate 5V and the other to generate 3.3V.
I like these part positions as they allow for the most direct routing and I believe also cover all the layout guidelines. The feedback resistors are a little farther away from the switcher than I'd like but having them there means a direct shot into the part for almost all signals.
Anyway, hoping for some feedback (pun intended!) so I can try and finish the board layout before the New Year.
Thanks & Have a Great 2013!!!
In general that looks ok. Make sure to get c1 and c2 as close as possible to the IC. The SW node copper area should be as small as practical without making it long and thin (short and wide is better). So you may want to look at the U1, C5, L1 relationship. I would probably be inclined to move L1 closer and move C5 up. To minimize the output circulating path, you may want to rotate L1 90 degrees so the output side is facing down. you can then move the output caps to the left of the inductor rather than the right with the ground side facing up.
John Tucker
Consumer DC/DC Applications
Hi John:
OK, if I move C5 above L1 (after rotating it 90 degrees) I can then move L1 very close to U1. By doing that I wouldn't have enough room to fit all 4 output caps to the left of L1. Would it be better to move R1 and R4 so all 4 output caps fit basically below U1 or would it be alright to split the output caps and put 2 on either side of L1?
You can array them in different ways, the main thing is to place them so the loop from SW to L1 to Cout and back to the IC ground has a small loop area.
OK, gotcha. I didn't completely move C5 out of the way because I wanted to make sure that I had enough room to do a big copper area for Vin.
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Getting ready to do some copper pours and I thought it wouldn't hurt to have a 2nd pair of eyes take another look at the layout if you don't mind.