ART10012T/CK IRF [International Rectifier], ART10012T/CK Datasheet - Page 8

• Manufacturer Part Number: ART10012T/CK
• Description: HYBRID - HIGH RELIABILITY RADIATION HARDENED DC/DC CONVERTER
• Manufacturer: IRF [International Rectifier]

Synchronization
The sync input port permits synchronization of an ART
converter to any compatible external frequency source
operating in the band of 225 to 310 KHz. The synchronization
input is edge triggered with synchronization initiated on
the negative transition. This input signal should be a
negative going pulse referenced to the input return and
have a 20% to 80% duty cycle. Compatibility requires the
negative transition time to be less than 100 ns with minimum
pulse amplitude of +4.25 volts referred to the input return.
In the absence of an external source, the converter will
revert to its own internally set frequency. If external
synchronization is not desired, the sync in pin may be left
open (unconnected) permitting the converter to operate at
its’ own internally set frequency.
Systems using multiple convertors may dictate operating
the group at a common switching frequency. To
accomodate this requirement, the ART28XXT converters
include a synchronization input (pin 4). Topology is
illustrated in Figure III.
Figure III. Synchronization Input Equivalent Circuit
Figure IV. Synchronization Output Equivalent Circuit
ART28XXT Series
An additional feature is a synchronization output (pin 5)
permitting multiple ART28XX converters in a system to be
synchronized to one of the converters in the set. See
Figure IV.
8
Output
Return
Sync
Input
Return
Sync
Input
Input
5
2
4K
6K
+10V
47pf
2N2222
5K
10pf
10K
To Internal
10K
Clock
2N2907A
+10V
Although no special provision for forced current sharing
has been incorporated in the ART28XXT series, multiple
units may be operated in parallel for increased output power
applications. The 5.0 volt outputs will typically share to
within approximately 10% of their full load capability and
the dual (±15 volt) outputs will typically share to within
50% of their full load. Load sharing is a function of the
individual impedance of each output and the converter
with the highest nominal set voltage will furnish the
predominant load current.
To attenuate input ripple current, the ART28XXT series
converters incorporate a two-stage LC input filter. The
elements of this filter comprise the dominant input load
impedance characteristic, and therefore determine the
nature of the current inrush at turn-on. The input filter
circuit elements are as shown in Figure V.
Input Undervoltage Protection
An additional feature is a synchronization output (pin 5)
permitting multiple Protection against overload or short
circuit on any output is provided in the ART28XXT converter
series. This protection is implemented by sensing primary
switching current and, when a load fault condition is
detected, pulse width is limited by the protection circuitry.
The converter is able to operate continuously with a load
fault witout damage or exceeding derating limits.
Parallel Operation
A minimum voltage is required at the input of the converter
to initiate operation. This voltage is set to a nominal value
of 16.8 volts. To preclude the possibility of noise or other
variations at the input falsely initiating and halting converter
operation, a hysteresis of approximately 1.0 volts is
incorporated in this circuit. The converter is guaranteed to
operate at 19 Volts input under all specified conditions.
Input Filter
Output Load Fault Protection
Pin 1
Pin 2
Figure V. Input Filter Circuit
4.7 µH
34 µH
1.35Ω
www.irf.com
5.4 µfd