M3G500512T_16 Datasheet, PDF (2/10 Pages) International Rectifier – HYBRID-HIGH RELIABILITY RADIATION HARDENED DC-DC CONVERTER

M3G-SERIES
(50V Input, Triple Output)
Circuit Description
The M3G-Series converters utilize a single-ended forward
topology with resonant reset. The nominal switching frequency
is 500 kHz.. Electrical isolation and tight output regulation are
achieved through the use of a magnetically coupled feedback.
Voltage feed-forward with duty factor limiting provides high
line rejection.
An internal EMI filter reduces the conducted emissions to
less than 5mArms on the input power leads. A two stage
output filter reduces the typical output ripple to less than
20mV peak-to-peak.
The main (+5 volt) output is regulated by the control loop
and typically exhibits better than 1% regulation. The auxiliary
(±12 volt or ±15 volt) outputs are maintained through tight
coupling in the power transformer and main output filter
inductor and typically exhibit better than 5% regulation.
The main output and auxiliary outputs are isolated from
each other
Output current is limited under any load fault condition to
approximately 125% of rated. An overload condition causes
the converter output to behave like a constant current
source with the output voltage dropping below nominal.
The converter will resume normal operation when the load
current is reduced below the current limit point. This protects
the converter from both overload and short circuit conditions.
The current limit point exhibits a slightly negative temperature
coefficient to reduce the possibility of thermal runaway
An under-voltage lockout circuit prohibits the converter
from operating when the line voltage is too low to maintain
the output voltage. The converter will not start until the line
voltage rises to approximately 36 volts and will shut down
when the input voltage drops below 34 volts. This two
volts of hysteresis reduces the possibility of line noise
interfering with the converter’s start-up and shut down.
.
An external inhibit port is provided to control converter
operation. The nominal threshold relative to the input
return (pin 2) is 1.4V. If 2.0 volts or greater are applied
to the Inhibit pin (pin 3) then the converter will operate
normally. A voltage of 0.8V or less will cause the converter to
shut-down. The pin may be left open for normal operation
and has a nominal open circuit voltage of 4.0V.
Synchronization input and output allow multiple converters to
operate at a common switching frequency. Converters
can be synchronized to one another or to an externally
provided clock. This can be used to eliminate beat frequency
noise or to avoid creating noise at certain frequencies for
sensitive systems.
Design Methodology
The M3G-Series was developed using a proven conservative
design methodology which includes selecting radiation
tolerant and established reliability components and fully
de-rating to the requirements of MIL-STD-975 and MIL-
STD-1547 except for the CDR type ceramic capacitors, a
capacitor with 50V rating is used for in-circuit voltage
stress of less than 10V. Careful sizing of decoupling
capacitors and current limiting resistors minimizes the
possibility of photo-current burn-out. Heavy de-rating of
the radiation hardened power MOSFET virtually eliminates the
possibility of SEGR and SEB.A magnetic feedback circuit
is utilized instead of opto-couplers to minimize temperature,
radiation and aging sensitivity. PSPICE and Rad SPICE
were used extensively to predict and optimize circuit performance
for both beginning and end-of-life. Thorough design analyses
include Radiation Susceptibility (TREE), Worst Case, Stress,
Thermal, Failure Modes and Effects (FMEA) and Reliability
(MTBF).
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2016-06-30