Data Sheet
Austin MegaLynxTM Non-Isolated dc-dc Power Modules:
4.5 – 5.5Vdc input; 0.8 – 3.63Vdc output; 30A output current
6.0 – 14Vdc input; 0.8 – 5.5Vdc output; 25A output current
June 3, 2009
For proper voltage sequencing, first, input voltage is
applied to the module. The On/Off pin of the module is
left unconnected or tied to GND for negative logic
modules so that the module is ON by default. After
applying input voltage to the module, a delay of 10msec
minimum is required before applying voltage on the SEQ
pin. During this delay time, the SEQ pin should be kept
at a voltage of 50mV (± 20 mV). After the 10msec delay,
the voltage applied to the SEQ pin is allowed to vary and
the output voltage of the module will track this voltage on
a one-to-one volt basis until the output reaches the set-
point voltage. To initiate simultaneous shutdown of the
modules, the sequence pin voltage is lowered in a
controlled manner. The output voltages of the modules
track the sequence pin voltage when it falls below their
set-point voltages. A valid input voltage must be
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
converters enabled and disabled using the on/off
pin.
maintained until the tracking and output voltages reach
zero to ensure a controlled shutdown of the modules.
For a more detailed description of sequencing, please
refer to Application Note AN04-008 titled “Guidelines
for Sequencing of Multiple Modules”.
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.
When using the EZ-SEQUENCETM feature to control
start-up of the module, pre-bias immunity 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
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
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15
LINEAGEPOWER [ LINEAGE POWER CORPORATION ]
