Hi all, I need to make a triple output buck converter. The clocks are going to be synced but I have the choice of aligning all switching edges with each other with 0 and 180 degree phase alignnments to eliminate beat frequency effects (clock jitter and high frequency PSRR problems as described here)
http://wwwd.national.com/national/PowerMB.nsf/(approved-attachments)/05F8ABEBFF14659F8825710F005C7DA1/$File/Beat+Frequency+Solution.pdf
Or I have the choice to phase align the clocks of the 3 outputs in 0, 120, and 240 degree phase alignments to reduce the RMS ripple on the input capacitor.
I'm not quite sure which one tends to be a better choice. Obviously phase aligning everything to be the same will eliminate beat frequencies but make input ripple worse. But that can be improved if you align the two lower current phases together and have the third higher current output 180 degrees phase shifted relative to that. So I'm not sure whether I should:
-0 degree phase for the two lower current outputs, and 180 degree phase for the higher current output
-0, 120, and 240 phase shift for everything
http://wwwd.national.com/national/PowerMB.nsf/(approved-attachments)/05F8ABEBFF14659F8825710F005C7DA1/$File/Beat+Frequency+Solution.pdf
Or I have the choice to phase align the clocks of the 3 outputs in 0, 120, and 240 degree phase alignments to reduce the RMS ripple on the input capacitor.
I'm not quite sure which one tends to be a better choice. Obviously phase aligning everything to be the same will eliminate beat frequencies but make input ripple worse. But that can be improved if you align the two lower current phases together and have the third higher current output 180 degrees phase shifted relative to that. So I'm not sure whether I should:
-0 degree phase for the two lower current outputs, and 180 degree phase for the higher current output
-0, 120, and 240 phase shift for everything