V048F480T006 Datasheet, PDF (9/11 Pages) Vicor Corporation – VTM Current Multiplier

Application Note
Parallel Operation
In applications requiring higher current or redundancy, VTM™ current
multipliers can be operated in parallel without adding control circuitry
or signal lines. To maximize current sharing accuracy, it is imperative
that the source and load impedance on each VTM™ module in a
parallel array be equal. If the modules are being fed by an upstream
PRM™ regulator, the VC nodes of all VTM modules must be connected
to the PRM module VC.
To achieve matched impedances, dedicated power planes within the PC
board should be used for the output and output return paths to the
array of paralleled VTMs. This technique is preferable to using traces of
varying size and length.
The VTM module power train and control architecture allow
bi-directional power transfer when the module is operating within its
specified ranges. Bi-directional power processing improves transient
response in the event of an output load dump. The module may
operate in reverse, returning output power back to the input source. It
does so efficiently.
Thermal Considerations
V•I Chip™ products are multi-chip modules whose temperature
distribution varies greatly for each part number as well as with the
input /output conditions, thermal management and environmental
conditions. Maintaining the top of the V048F480T006 case to less than
100°C will keep all junctions within the V•I Chip module below 125°C
for most applications. The percent of total heat dissipated through the
top surface versus through the J-lead is entirely dependent on the
particular mechanical and thermal environment. The heat dissipated
through the top surface is typically 60%. The heat dissipated through
the J-lead onto the PCB board surface is typically 40%. Use 100% top
surface dissipation when designing for a conservative cooling solution.
It is not recommended to use a V•I Chip module for an extended
period of time at full load without proper heat sinking.
Input Impedance Recommendations
To take full advantage of the current multiplier’s capabilities, the
impedance of the source (input source plus the PC board impedance)
must be low over a range from DC to 5 MHz. Input bypass capacitance
may be added to improve transient performance or compensate for
high source impedance. The VTM module has extremely wide
bandwidth so the source response to transients is usually the limiting
factor in overall output response of the module.
Anomalies in the response of the source will appear at the output of
the VTM module, multiplied by its K factor of 1 . The DC resistance
of the source should be kept as low as possible to minimize voltage
deviations on the input to the module. If the module is going to be
operating close to the high limit of its input range, make sure input
voltage deviations will not trigger the input overvoltage turn-off
threshold.
Input Fuse Recommendations
V•I Chip products are not internally fused in order to provide flexibility
in configuring power systems. However, input line fusing of V•I Chip
modules must always be incorporated within the power system. A fast
acting fuse is required to meet safety agency Conditions of
Acceptability. The input line fuse should be placed in series with the +In
port.
Application Notes
For application notes on soldering, thermal management, board layout,
and system design click on the link below:
http://www.vicorpower.com/technical_library/application_information/chips/
Input reflected ripple
measurement point
F1
10A
Fuse
C1
47 µF
Al electrolytic
C2
0.47 µF
ceramic
14 V ^+–
Figure 15 — VTM™ module test circuit
+Out
+In
-Out
TM
VC
VTM™
PC
+Out
K
Ro ^-In
-Out
R3
5 mΩ
C3
9.4 µF
+
Load
Notes:
– C3 should be placed close
to the load
R3 may be ESR of C3 or a
separate damping resistor.
vicorpower.com 800-735-6200
VTM™ Current Multiplier
V048F480T006
Rev. 3.1
Page 9 of 11