Application Note (continued)
The thermal resistance of the PCB to the surrounding
environment in proximity to V•I Chips may be reduced by low
profile heat sinks surface mounted to the PCB.
The PCB may also be coupled to a cold plate by low thermal
resistance standoff elements as a means of achieving effective
cooling for an array of V•I Chips, without a direct interface to
their case.
external thermal resistances provides an efficient thermal
management strategy as it reduces total thermal resistance. This
may be readily estimated as the parallel network of two pairs of
series configured resistors.
The TM (Temperature Monitor) port monitors the V•I Chip
junction temperature and provides feedback and validation of the
thermal management of V•I Chips, as applied in diverse power
systems and environments.
CASE 3—Combined direct convection to the air and conduction
to the PCB.
Parallel use of the V•I Chip internal thermal resistances
(including Junction-to-Case and Junction-to-BGA) in series with
V•I Chip BUS CONVERTER LEVEL 1 DC BEHAVIORAL MODEL for 48 V to 12 V, 200 W
ROUT
20 mΩ
IOUT
+
+
•
V I
1
1
/
/
4 • Iout
4 • Vin
+
–
+
–
VOUT
VIN
Q
I
52 mA
K
-
–
©
Figure 26—This model characterizes the DC operation of the V•I Chip bus converter, including the converter transfer function
and its losses. The model enables estimates or simulations of output voltage as a function of input voltage and output load, as
well as total converter power dissipation or heat generation.
V•I Chip BUS CONVERTER LEVEL 2 TRANSIENT BEHAVIORAL MODEL for 48 V to 12 V, 200 W
8.5 nH
ROUT
IOUT
= 1.6 nH
LOUT
IN
L
= 20 nH
+
20 mΩ
+
R
COUT
R
40 mΩ
4• Vin
/
CIN
•
V I
0.3 mΩ
2.0 mΩ
1
1
/
4 • Iout
+
–
+
–
2 µF
CIN
COUT
12 µF
VOUT
VIN
IQ
52 mA
K
–
–
©
Figure 27—This model characterizes the AC operation of the V•I Chip bus converter including response to output load or input
voltage transients or steady state modulations. The model enables estimates or simulations of input and output voltages under
transient conditions, including response to a stepped load with or without external filtering elements.
Vicor Corporation
Tel: 800-735-6200
vicorpower.com
V•I Chip Bus Converter
B048K120T20
Rev. 2.2
Page 13 of 16
45
VICOR [ VICOR CORPORATION ]
