Data Sheet
Austin MegaLynxTM SMT: Non-Isolated DC-DC Power Modules:
4.5 – 5.5Vdc input; 0.8 to 3.63Vdc Output; 30A output current
6.0 – 14Vdc Input; 0.8Vdc to 3.63Vdc Output; 20/30A output
June 3, 2009
feature during start-up is disabled. The pre-bias
immunity feature of the module relies on the module
being in the diode-mode during start-up. When
using the EZ-SEQUENCETM feature, modules goes
through an internal set-up time of 10msec, and will
be in synchronous rectification mode when voltage
at the SEQ pin is applied. This will result in sinking
current in the module if pre-bias voltage is present
at the output of the module. When pre-bias
converters enabled and disabled using the
on/off pin.
•
The share bus is not designed for redundant
operation and the system will be non-functional
upon failure of one of the unit when multiple
units are in parallel. In particular, if one of the
converters shuts down during operation, the
other converters may also shut down due to
their outputs hitting current limit. In such a
situation, unless a coordinated restart is
ensured, the system may never properly restart
since different converters will try to restart at
different times causing an overload condition
and subsequent shutdown. This situation can
be avoided by having an external output
voltage monitor circuit that detects a shutdown
condition and forces all converters to shut
down and restart together.
immunity during start-up is required, the EZ-
SEQUENCETM feature must be disabled.
Active Load Sharing (-P Option)
For additional power requirements, the Austin
MegaLynx series power module is also available
with a parallel option. Up to five modules can be
configured, in parallel, with active load sharing.
Good layout techniques should be observed when
using multiple units in parallel. To implement forced
load sharing, the following connections should be
made:
•
The share pins of all units in parallel must be
connected together. The path of these
connections should be as direct as possible.
•
All remote-sense pins should be connected to
the power bus at the same point, i.e., connect
all the SENSE(+) pins to the (+) side of the bus.
Close proximity and directness are necessary
for good noise immunity
Some special considerations apply for design of
converters in parallel operation:
•
When sizing the number of modules required
for parallel operation, take note of the fact that
current sharing has some tolerance. In
addition, under transient condtions such as a
dynamic load change and during startup, all
converter output currents will not be equal. To
allow for such variation and avoid the likelihood
of a converter shutting off due to a current
overload, the total capacity of the paralleled
system should be no more than 75% of the
sum of the individual converters. As an
example, for a system of four ATS030A0X3-SR
converters the parallel, the total current drawn
should be less that 75% of (4 x 30A) , i.e. less
than 90A.
•
All modules should be turned on and off
together. This is so that all modules come up at
the same time avoiding the problem of one
converter sourcing current into the other
leading to an overcurrent trip condition. To
ensure that all modules come up
simultaneously, the on/off pins of all paralleled
converters should be tied together and the
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18
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