F
EATURES
• –55°C to +125°C operation
• 19 to 56 VDC input
• Magnetic feedback
• Topology – Two-Phased Flyback
• 80 V for 100 ms transient protection
• Inhibit function and output trim
• Indefinite short circuit protection
• Radiation hardened to
3x10
12
neutrons/sq cm neutron
fluence
10
11
rads(Si)/sec dose rate
3x10
5
rads(Si) total dose
SEU 115 MeV cm
2
/mg
• Meets MIL-STD-704 emergency
operation and transient standards
Size (max.):
• No minimum load required
• 5 port isolated design
Weight:
Screening:
• Isolated synchronization input
PRELIMINARY
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
SMRT SERIES
24 TO 50 WATT
MODELS
VDC O
UTPUT
SINGLE
3.3
5
28
TRIPLE
+3.3 & ±12
+5 & ±12
+5 & ±15
DUAL
±5
±12
±15
QUAD
±5 & ±12
±5 & ±15
2.705 x 2.205 x 0.400 inches (68.71 x 56.01 x 38.23 x 10.16 mm)
See cases “S maximum dimensions” and “S1” for dimensions.
100 grams maximum
Space prototype, Class H, or Class K (MIL-PRF-38534)
Radiation hardness levels O or R
See “QA Screening: Class H and K, QML” for more information.
Available configurations: OO, HO, HR, KR
low (≤ 0.8 V) signal is applied to the TTL open collector compatible
inhibit pin. In the inhibit mode the inhibit pin current requirement is
less than –2 mA. The converter resumes normal operation when a
logic high (≥ 2.4 V) signal or open circuit is applied to the inhibit pin.
The open circuit voltage of the inhibit is 5 to 6 volts.The maximum
allowable voltage applied to the inhibit pin is 10 VDC.
DESCRIPTION
The SMRT Series™ of DC/DC converters offers up to 50 watts of
power in a radiation hardened design. The low profile SMRT
converters are manufactured in Interpoint’s fully certified and quali-
fied MIL-STD-1772 production facility and packaged in hermetically
sealed steel cases. They are ideal for use in programs requiring
high reliability, small size, and high levels of radiation hardening.
The SMRT converters are switching regulators which use a two-
phase, phase shifted flyback design with a nominal switching
frequency of 275 kHz, typical. Close regulation is maintained with
advanced constant frequency pulse width modulation design tech-
niques. The SMRT’s feed-forward compensation topology and
discontinuous topology provide high levels (80 dB nominal) of input-
to-output ripple rejection. No minimum load is required.
Two independent feedback loops are used to regulate either a
single main output and dual outputs or a configuration of two sets
of dual outputs with each set independently regulated. Each set of
outputs are electrically isolated from each other and from the input.
This product configuration eliminates cross regulation effects
between output sets. Configurations include:
• Single Output: Two-phased single output
• Dual Output: Dual outputs each with independent regulation and
isolation.
• Triple Output: One main (independent) output and two outputs
(±).
• Quad Output: Two independent sets of dual outputs
S
YNCHRONIZATION
An isolated sync input allows this input to be connected to any of
the devices three returns. It can be referred to the input return or
any of the output returns. Input into this pin is limited by a series 1k
ohm resistance.
O
UTPUT
V
OLTAGE
T
RIM
The output voltage of each set can be trimmed upward by as much
as 20% of nominal. The following are “sets” of voltages in relation
to trim:
• Triple output models: Main output is one set, the dual outputs are
another set.
• Dual outputs: Each output is a “set.”
• Single: One set
R
ADIATION
H
ARDENED
The SMRT DC/DC converters are designed to provide continuous
normal operation through radiation levels associated with proximity
to thermonuclear events. The converters will operate normally in
environments with up to 3x10
12
neutrons per square centimeter
neutron fluence, 10
11
rads (Si) per second dose rate, and 3x10
5
rads (Si) total dose. These levels of radiation tolerance make the
SMRT converters suitable for electronics in tactical programs where
operation in high radiation environments is required.
At the highest dose rate (10
11
rads (Si)/sec dose rate) there will be
an upset resulting in a dip in the voltage. This is non-destructive to
the unit. The converter will operate through the upset.
U
NDERVOLTAGE
L
OCKOUT
The converters have an undervoltage lockout that will allow power
conversion at 16 volts on a rising input voltage and a conversions
shut-down on a falling voltage at approximately 14.5 volts. Rather
than a hard shut-down, there is approximately 0.5 volts of progres-
sive turn-on and turn-off to minimize potential source impedance
oscillations for high source impedance.
I
NHIBIT
F
UNCTION
The SMRT Series incorporates an inhibit terminal that can be used
to disable internal switching. The converter is inhibited when a logic
EMI
The SMRT has a built-in EMI input filter which brings the conducted
emissions into compliance with both methods of MIL-STD-461, revi-
sions D and E, CE03 and CE102.
SMRT SERIES
24 TO 50 WATTS
ABSOLUTE MAXIMUM RATINGS
DC/DC C
ONVERTERS
SYNC AND INHIBIT
Sync In 225-350 kHz typical
• Duty cycle 20% min, 80% max
• 2.5V minimum amplitude
• 10V p-p maximum amplitude
• Can be referenced to any return
Inhibit TTL
• Logic low (output disabled)
INH1 referenced to input common
Logic low 0.8 V max
Inhibit pin current < 2mA
• Logic high (output enabled)
Open collector
Logic high >3.0V
Not to exeed 10V
Preliminary
TYPICAL CHARACTERISTICS
Output Voltage Temperature Coefficient
• 150 ppm/°C max
Current Limit
• 125% of full load typical
Isolation
• 100 megohm minimum at 500 V
Conversion Frequency
• 300 kHz. typical
Inhibit Pin Voltage (unit enabled)
• 5 to 6 V
Radiation (will operate through)
• Neutron fluence 3x10
12
neutrons/ sq. cm.
• Radiation dose rate 10
11
rads (Si) /sec
• Total dose 10
5
rads (Si)
• SEU 115 MeV-cm
2
/mg
Power Dissipation (Pd)
• 10 W
Output Power
• up to 50 watts depending on model
Lead Soldering Temperature (10 sec per lead)
• 300°C
Storage Temperature Range (Case)
• –65°C to +150°C
RECOMMENDED OPERATING CONDITIONS
Input Voltage Range
• Continuous 19 to 56 VDC
Case Operating Temperature (Tc)
• –55°C to +125°C full power
• –55°C to +135°C absolute
INPUT
Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, unless otherwise specified.
ALL MODELS
MIN
TYP
MAX
19
0
—
—
—
28
—
—
—
—
56
80
100
50
10
PARAMETER
INPUT VOLTAGE
1
NO LOAD TO FULL
INPUT CURRENT
INPUT RIPPLE
CURRENT
2
CONDITIONS
CONTINUOUS
TRANSIENT 100 ms
NO LOAD
INHIBITED
1
10 kHz - 50 MHz
UNITS
VDC
V
mA
mA
mA p-p
Notes
1. Converter should not be inhibited or operated below 16 Vin above 2x10
4
rads (Si) total dose.
2. Converters meet MIL-STD-461 specification. The actual value of input ripple current is much
less, the limit in the characteristic table is based on measurement resolution.
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