For the 2-phase application, the
design process is similar to that of the single phase, except:
- In selecting the voltage loop
compensation, N = 2 divides the effective current sense amplifier gain in half
as the two phases operate in parallel, each delivering equal current, doubling
the current gain of the converter.
- For ceramic input bypassing capacitors, TI
recommends that each phase have sufficient bypassing to support each phase as if
the phase was a single-phase output. While there is some channel to channel
current sharing, layout and trace inductance often results in actual ripple
current sharing being significantly lower than the desired input ripple
cancellation.
- MSEL2 of the primary channel (MSEL2_A) is
selected for a 2-phase converter with 3ms TON_RISE and the maximum current limit
by being left open.
- VSEL and ADRSEL of the primary
channel are programed the same as a single phase converter.
- MSEL2 of the follower channel (MSEL2_B) is float
to select follower of a 2-phase converter with 30/39A current limit
setting.
- GOSNS/FLWR_B is pulled up to BP1V5 to set channel
B to a follower, using the Channel A voltage regulation and error amplifier as
well as PMBus interface.
- VSHARE_A and VSHARE_B are
connected together along with BCX_CLK A and B, and BCX_DAT A and B.
- MSEL1, VSEL, ADRSEL, PGOOD,
PMB_CLK, and PMB_DAT on Channel B are all unused, and connected to GND.