JFC050C Datasheet, PDF (12/20 Pages) Tyco Electronics – dc-dc Converters; 18 to 36 Vdc Input; 15 Vdc Output; 50 W to 100 W

JFC050C, JFC075C, JFC100C Power Modules:
dc-dc Converters; 18 to 36 Vdc Input, 15 Vdc Output; 50 W to 100 W
Data Sheet
October 1999
Feature Descriptions (continued)
Module Synchronization
Any module can be synchronized to any other module
or to an external clock using the SYNC IN or SYNC
OUT pins. The modules are not designed to operate in
a master/slave configuration; that is, if one module fails,
the other modules will continue to operate.
SYNC IN Pin
This pin can be connected either to an external clock or
directly to the SYNC OUT pin of another JFx150x or
Fx300x module.
If an external clock signal is applied to the SYNC IN
pin, the signal must be a 500 kHz (±50 kHz) square
wave with a 4 Vp-p amplitude. Operation outside this
frequency band will detrimentally affect the perfor-
mance of the module and must be avoided.
If the SYNC IN pin is connected to the SYNC OUT pin
of another module, the connection should be as direct
as possible, and the VI(–) pins of the modules must be
shorted together.
Unused SYNC IN pins should be tied to VI(–). If the
SYNC IN pin is unused, the module will operate from
its own internal clock.
remote sense, the forward-voltage drops across the
Schottky diodes do not affect the set point of the volt-
age applied to the load. For additional power require-
ments, where multiple units are used to develop
combined power in excess of the rated maximum, the
Schottky diodes are not needed.
An internal anti-rollback circuit prevents either output
voltage from falling more than 1 V below the other dur-
ing light load operation.
Good layout techniques should be observed for noise
immunity. To implement forced load sharing, the follow-
ing connections must be made:
s The parallel pins of all units must be connected
together. The paths of these connections should be
as direct as possible.
s All remote-sense pins must be connected to the
power bus at the same point. That is, connect all
remote-sense (+) pins to the (+) side of the power
bus at the same point, and connect all remote-sense
(–) pins to the (–) side of the power bus at the same
point. Close proximity and directness are necessary
for good noise immunity.
s Add a 1000 pF capacitor across the PARALLEL pin
and SENSE(–) pin of each module. Locate the
capacitor as close to the module as possible.
SYNC OUT Pin
This pin contains a clock signal referenced to the VI(–)
pin. The frequency of this signal will equal either the
module’s internal clock frequency or the frequency estab-
lished by an external clock applied to the SYNC IN pin.
When synchronizing several modules together, the
modules can be connected in a daisy-chain fashion
where the SYNC OUT pin of one module is connected
to the SYNC IN pin of another module. Each module in
the chain will synchronize to the frequency of the first
module in the chain.
To avoid loading effects, ensure that the SYNC OUT
pin of any one module is connected to the SYNC IN pin
of only one module. Any number of modules can be
synchronized in this daisy-chain fashion.
Forced Load Sharing (Parallel Operation)
For either redundant operation or additional power
requirements, the power module can be configured for
parallel operation with forced load sharing (see
Figure 17). For a typical redundant configuration,
Schottky diodes or an equivalent should be used to
protect against short-circuit conditions. Because of the
PARALLEL
SENSE(+)
SENSE(–)
CASE VO(+)
ON/OFF
VI(+) VO(–)
VI(–)
PARALLEL
SENSE(+)
SENSE(–)
CASE VO(+)
ON/OFF
VI(+) VO(–)
VI(–)
8-581 (C)
Figure 17. Wiring Configuration for Redundant
Parallel Operation
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Tyco Electronics Corp.