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LTM4625
11
Rev D
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of phases used (assuming that the input voltage is greater
than the number of phases used times the output voltage).
The output ripple amplitude is also reduced by the number
of phases used when all of the outputs are tied together
to achieve a single high output current design.
The LTM4625 device is an inherently current mode con
-
trolled device, so parallel modules will have very good
current sharing. This will balance the thermals on the
design. Please tie the RUN, TRACK/SS, FB and COMP pins
of each paralleling channel together. Figure 23 shows an
example of parallel operation and pin connection.
Input RMS Ripple Current Cancellation
Application Note 77 provides a detailed explanation of
multiphase operation. The input RMS ripple current can
-
cellation mathematical derivations are presented, and a
graph is displayed representing the RMS ripple current
reduction as a function of the number of interleaved
phases. Figure 3 shows this graph.
APPLICATIONS INFORMATION
Figure 2. 4-Phase, 6-Phase Operation
Figure 3. RMS Input Ripple Current to DC Load Current Ratio as a Function of Duty Cycle
4625 F02
CLKIN
PHMODE
CLKOUT
0 90 180 270
+90 +90 +90
PHASE 4PHASE 3PHASE 2PHASE 1
CLKIN
PHMODE
CLKOUT CLKIN
PHMODE
CLKOUT CLKIN
PHMODE
CLKOUT
CLKIN
PHMODE
CLKOUT
120 240
(420)
60 180
+120 +180 +120
PHASE 4
INTV
CC
INTV
CC
PHASE 2PHASE 5PHASE 3
CLKIN
PHMODE
CLKOUT CLKIN
PHMODE
CLKOUT CLKIN
PHMODE
CLKOUT
300
+120
PHASE 6
CLKIN
PHMODE
CLKOUT
0
PHASE 1
CLKIN
PHMODE
CLKOUT
+120
0.75
0.8
4625 F03
0.70.650.60.550.50.450.40.350.30.250.20.150.1
0.85
0.9
DUTY CYCLE (V
OUT
/V
IN
)
0
DC LOAD CURRENT
RMS INPUT RIPPLE CURRENT
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
1 PHASE
2 PHASE
3 PHASE
4 PHASE
6 PHASE
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