GE Industrial Solutions GigaTLynx - Manual (Page 11)

Data Sheet
September 7, 2011 GigaTLynx TM SMT Non-isolated Power Modules:
4.5 – 14Vdc input; 0.7Vdc to 2.0Vdc, 50A Output
LINEAGE POWER
11
output reaches the set-point voltage. To initiate
simultaneous shutdown of the modules, the SEQ pin
voltage is lowered in a controlled manner. The output
voltage of the modules tracks the voltages below their
set-point voltages on a one-to-one basis. A valid input
voltage must be maintained until the tracking and output
voltages reach ground potential.
When using the EZ-SEQUENCE
TM feature to control
start-up of the module, pre-bias immunity 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-SEQUENCE
TM feature,
modules goes through an internal set-up time of 10msec,
and will be in synchronous rectification mode when the
voltage at the SEQ pin is applied. This will result in the
module sinking current if a pre-bias voltage is present at
the output of the module. When pre-bias immunity during
start-up is required, the EZ-SEQUENCE
TM feature must
be disabled. For additional guidelines on using the EZ-
SEQUENCE
TM feature please contact the Lineage Power
technical representative for additional information.
Active Load Sharing (-P Option)
For additional power requirements, the Giga TLynx TM
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 conditions 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 90% of the sum of
the individual converters. As an example, for a
system of four Giga TLynx
TM converters in parallel,
the total current drawn should be less that 90% of (4
x 50A) , i.e. less than 180A.
• 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.
• 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 not using the active load share feature, share pins
should be left unconnected.
Power Good
The Giga TLynx TM modules provide a Power Good
(PGOOD) signal to indicate that the output voltage is
within the regulation limits of the power module. The
PGOOD signal will be de-asserted to a low state if any
condition such as overtemperature, overcurrent or loss of
regulation occurs that would result in the output voltage
going ±1
2.5 % outside the setpoint value. The PGOOD
terminal is internally pulled-up and provides a voltage of
~5V, when asserted, thus eliminating the need for an
external source and pull-up resistor. Additional external
drive capability can be provided to the PGOOD terminal
by using a source less than 5V and a suitable pull-up
resistor to keep the overall external current below 4.5mA
Tunable Loop
The Giga TLynx TM modules have a new feature that
optimizes transient response of the module called
Tunable Loop
TM .
External capacitors are usually added to the output of the
module for two reasons: to reduce output ripple and
noise (see Fig. 23) and to reduce output voltage
deviations from the steady-state value in the presence of
dynamic load current changes. Adding external
capacitance however affects the voltage control loop of
the module, typically causing the loop to slow down with
sluggish response. Larger values of external capacitance
could also cause the module to become unstable.
The Tunable Loop TM allows the user to externally adjust
the voltage control loop to match the filter network
connected to the output of the module. The Tunable
Loop
TM is implemented by connecting a series R-C
between the SENSE and TRIM+ pins of the module, as
shown in Fig. 28. This R-C allows the user to externally