Datasheet

LTM4620A
16
4620afb
For more information www.linear.com/LTM4620A
APPLICATIONS INFORMATION
Figure 4. Input RMS Current Ratios to DC Load Current as a Function of Duty Cycle
DUTY FACTOR (V
OUT
/V
IN
)
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8
0.85 0.9
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
4620A F04
RMS INPUT RIPPLE CURRENT
DC LOAD CURRENT
6-PHASE
4-PHASE
3-PHASE
2-PHASE
1-PHASE
Input RMS Ripple Current Cancellation
Application Note 77 provides a detailed explanation of
multiphase operation. The input RMS ripple current cancel
-
lation 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 4
shows this graph.
Frequency Selection and Phase-Lock Loop
(MODE/PLLIN and f
SET
Pins)
The LTM4620A device is operated over a range of frequen-
cies to
improve power conversion efficiency. It is recom-
mended
to operate the lower output voltages or lower
duty
cycle conversions at lower frequencies to improve
efficiency by lowering power MOSFET switching losses.
Higher output voltages or higher duty cycle conversions
can be operated at higher frequencies to limit inductor
ripple current. The efficiency graphs will show an operating
frequency chosen for that condition. Select frequency in
reference to the highest output voltage.