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AFC461 Series
Device Synchronization
Whenever multiple DC/DC converters are utilized in
a single system, significant low frequency noise may
be generated due to slight difference in the switching
frequencies of the converters (beat frequency noise).
Because of the low frequency nature of this noise
(typically less than 10KHz), it is difficult to filter out
and may interfere with proper operation of sensitive
systems (communications, radar or telemetry).
International Rectifier offers an option, which
provides synchronization of multiple AHE/ATW type
converters, thus eliminating this type of noise. To
take advantage of this capability, the system designer
must assign one of the converters as the master.
Then, by definition, the remaining converters become
slaves and will operate at the masters’ switching
frequency. The user should be aware that the
synchronization system is fail-safe; that is, the slaves
will continue operating should the master frequency
be interrupted for any reason. The layout must be
such that the synchronization output of the master
device is connected to the synchronization input of
each slave device. It is advisable to keep this run
short to minimize the possibility of radiating the
250KHz switching frequency. A typical connection
is illustrated on the cover sheet of this document.
The appropriate converters must be ordered to take
advantage of this feature. After selecting the
converters required for the system, a ‘MSTR’ suffix
is added for the master converter part number and
an ‘SLV’ suffix is added for slave part number. See
Part Number section of the applicable converter data
sheets.
Refer to page 4 for Pin Designation Table
Block Diagram
1
5
3
2
4
11µF
0.2Ω
11µF
0.2Ω
1800
pFd
1800
pFd
1N5649A
10µH 5µH
0.1µF
+Input +Output
Case
Output
Return
Input
Return