Crane Aerospace & Electronics Power Solutions
sMFL sꢆꢇglꢂ ꢀꢇꢋ dꢉꢀl dc/dc cꢃꢇvꢂꢁꢅꢂꢁꢊ
28 VoLt input – 65 Watt
Features
pꢀꢁꢀllꢂl ꢃꢄꢂꢁꢀꢅꢆꢃꢇ wꢆꢅh ꢈꢉꢁꢁꢂꢇꢅ ꢊhꢀꢁꢂ, ꢉꢄ ꢅꢃ 3 ꢉꢇꢆꢅꢊ
(148 wꢀꢅꢅꢊ)
•ꢀ Operating temperature -55° to +125°C
•ꢀ Qualified to MIL-PRF-38534 Class H and K
•ꢀ Radiation hardness assurance (RHA) to level R 100 kRad(Si)
•ꢀ Input voltage range 16 to 40 VDC
•ꢀ Transient protection 50 V for 120 ms
•ꢀ Fully isolated, magnetic feedback
MODꢀLS
•ꢀ Fixed high frequency switching
VDc Ou t P u t
•ꢀ Remote sense and output trim on single output models
•ꢀ Inhibit function
SINꢁLꢀ
3.3
5
DꢂAL
±5
±12
±15
•ꢀ Synchronization input and output
12
15
•ꢀ Indefinite short circuit protection
•ꢀ High power density, 85% efficiency
description
similar to primary current mode control and allows for ease of
paralleling, but without the cost and complexity.
The SMFL Series™ 28-volt DC/DC converters are rated up to
65 watts output power over a -55° to +125°C temperature range
with a 28 VDC nominal input. On dual output models up to 70%
of the rated output power can be drawn from either the positive
or negative outputs. Current sharing allows the units to be paral-
leled for total power of up to 148 watts. The welded, hermetically
sealed package is only 3.0 x 1.5 x 0.40 inches, giving the series
an overall power density of up to 43 watts per cubic inch.
The constant frequency, pulse-width modulated converters use
a quasi-square wave single-ended forward design. Tight load
regulation is achieved through a wide-bandwidth magnetic feed-
back circuit. The output voltage on single SMFL models can
be trimmed to a specific output voltage by adding an external
resistor (see Figure 1 for resistor values).
Sc r e e n i n g
in h i b i t
SMFL converters, also available on SMD drawings, offer the
following screening options: Space Prototype (O), Class H, or
Class K. Radiation tolerant to Radiation Hardness Assurance
(RHA) levels of “-” (O), “P,” or “R,” per MIL-PRF-38534. Interpoint
model numbers use an “O” in the RHA designator position to
indicate the “-” (dash) Radiation Hardness Assurance level of
MIL-PRF-38534, which is defined as “no RHA”. See Screening
Tables 1 - 3 for more information.
The SMFL Series converters have two inhibit terminals (INH1
and INH2) that can be used to disable power conversion,
resulting in a very low quiescent input current and no generation
of switching noise. An active low (<0.8 volts) is required to inhibit
the converter between INH1 (pin 4) and Input Common (pin
2). An active low (<0.5 volts) is required to inhibit the converter
between INH2 (pin 12) and Output Common (pin 8). The appli-
cation of intermediate voltages to these pins (1.5 to 10.5 volts)
should be avoided.
De S i g n Fe a t u r e S
SMFL Series converters are switching regulators that use a
quasi-square wave, single ended forward converter design with a
constant switching frequency of 600 kHz typical.
Sy n c
Converters may be synced to an external clock (525 to 675 kHz)
or to one another by using the sync in or out pins. The nominal
free-run switching frequency is 600 kHz (see Application Note
titled “Inhibit and Synchronization”).
Isolation between input and output circuits is provided with a
transformer in the forward path and a wide bandwidth magnetic
coupling in the feedback control loop. The SMFL uses a unique
dual loop feedback technique that controls output current with
an inner feedback loop and an output voltage with a cascaded
voltage mode feedback loop. The additional secondary current
mode feedback loop improves transient response in a manner
cu r r e n t a n D Pa r a l l e l OP e r a t i O n
Multiple single output SMFL converters may be used in parallel
to drive a common load. In this mode of operation the load
current is shared by two or three SMFL converters. In current
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ꢀlectronics ꢁroup (Interpoint Brand)
POꢀBoxꢀ97005ꢀꢀ•ꢀꢀRedmondꢀWAꢀ98073-9705
425.882.3100ꢀꢀꢀ•ꢀꢀꢀpower@crane-eg.com
www.craneae.com/interpoint
SMFL Rev K - 20101209
The information in this document is a derivative of documents cleared
by the Department of Defense (DoD) Office of Security Review (OSR) for public release.
OSR case numbers 09-S-0996 dated March 13, 2009 and 09-S-1960 dated June 22, 2009.