IR35204 Datasheet, PDF (35/61 Pages) International Rectifier – 3+1 Dual Output Digital Multi-Phase Controller

3+1 Dual Output Digital Multi-Phase Controller
IR35204
Vdd
Idd
Figure 36: Zoomed-out view of Phase Shed/Add
Current limit and current balancing circuits remain active
during ATA events to prevent inductor saturation and
maintain even distribution of current across the active
phases.
The add/drop points for each phase can be set in 2A
increments from 0 to 62A per phase, with a fixed 4A
hysteresis. This results in a uniform per-phase current
density as the load increases or decreases.
Having DPC enabled optimizes the number of phases used
in real time, resulting in significant light and medium-load
efficiency improvements, as shown in Figure 37.
TABLE 25: SWITCHING PERIOD SKEW FACTOR OPTIONS
Switching Period Skew Range
Per-Phase
Starting Current
(A)
Fsw to 2 x Fsw
8
Fsw to 2 x Fsw
12
Fsw to 2 x Fsw
16
Fsw to 0.5 x Fsw
8
Fsw to 0.5 x Fsw
12
Fsw to 0.5 x Fsw
16
Note: Per Phase Current is limited to 62A in normal mode,
124A in doubler mode.
Using the above feature, the switching frequency can be
skewed based on the different register settings and per-
phase currents – the switching frequency skew factor versus
per-phase currents have been plotted in Figure 38 below for
3 of the register settings for reference.
Figure 37: Light Load Efficiency Improvement with DPC
VARIABLE FREQUENCY WITH LOAD ON LOOP1
In addition, the controller can be made to operate at a high
frequency when only a few phases are running, and lower
the frequency as more phases are added. This skew feature
is based on monitoring the per-phase current. The different
skews of the switching frequency available are:
Figure 38: Normalized Switching Frequency
DISCONTINUOUS MODE OPERATION - PS2, PS3
Under very light loads, the VR efficiency is dominated by
MOSFET switching losses. In PS2 mode, the IR35204
operates as a constant on-time controller where the user
sets the desired peak-to-peak ripple by programming an
error threshold and an on-time duration (Table 26). PS3
operation is identical to PS2, with the additional ability to
disable the internal current sense amplifiers within the
controller for further reduction in power consumption.
TABLE 26: PS2/PS3 MODE CONSTANT ON-TIME CONTROL
MTP Register
ni_thresh
de_thresh
Function
Sets the current level below which
PS2/PS3 is entered.
Sets the error threshold to start a pulse
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February 8, 2016 | V1.6