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Design Guide & Applications Manual
For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies
vicorpower.com 800-735-6200 Applications Engineering 1-800-927-9474 Rev. 2.1
Page 22 of 88
3 Amp Load 15 Amp Load 30 Amp Load
9. EMC Considerations
Differential-Mode Noise Filter. Differential-mode
conducted noise current is the component of current,
at the input power pin, which is opposite in direction or
phase with respect to the other input power pin.
All Vicor converters have an internal differential-mode LC
filter which, in conjunction with a small external capacitor
C1 (minimum value in µF) = 400 / Vin,
reduces differential-mode conducted noise. The external
capacitor should be placed close to the module to reduce
loop cross-sectional area.
Care should be taken to reduce the loop cross-sectional
area of differential-mode current flowing between the
source and C1. Since differential-mode input current is by
definition opposite in phase, twisting the input leads
causes noise cancellation. PCB power planes can reduce
radiated noise if the traces are on opposite sides of the
PCB directly over one another. If differential mode inductance
is used, it may be common to one or more modules.
C2
a
C1
C2
b
C3
b
C3
a
L1
C4
L2
C1 = 100 µF
C2
a
–
C2
b
= 4,700 pF (Vicor Part # 01000)
C3
a
–
C3
b
= 0.01 µF (Vicor Part # 04872)
C4 = 2.2 µF
L1 = 20 µH
L2 = 20 µH
+IN
GATE
IN
GATE
OUT
–IN
+OUT
+S
TRIM
–S
–OUT
Conditions
Light Load = 3 A
Nominal Load = 15 A
Full Load = 30 A
Figure 9–5 — Conducted noise, differential-mode filtering
Conducted Noise vs. Load
Differential-Mode Filter
Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output