Crane Aerospace & Electronics Power Solutions
sMFL single and dual dc/dc converters
28 VoLt input – 65 Watt
Features
• Operating temperature -55° to +125°C
parallel operation with current share, up to 3 units
(148 watts)
• Qualified to MIL-PRF-38534 Class H and K
• Input voltage range 16 to 40 VDC
• Fully isolated, magnetic feedback
• Fixed high frequency switching
• Inhibit function
• Radiation hardness assurance (RHA) to level R 100 kRad(Si)
• Transient protection 50 V for 120 ms
VDc O
utPut
SINgLe
3.3
5
12
15
DuAL
±5
±12
±15
MODeLS
• Remote sense and output trim on single output models
• Synchronization input and output
• Indefinite short circuit protection
• High power density, 85% efficiency
description
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.
similar to primary current mode control and allows for ease of
paralleling, but without the cost and complexity.
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).
S
creening
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.
i
nhibit
D
eSign
F
eatureS
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.
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.
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
Crane Aerospace & electronics
electronics group (Interpoint Brand)
PO Box 97005 • Redmond WA 98073-9705
425.882.3100 • power@crane-eg.com
www.craneae.com/interpoint
S
ync
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”).
c
urrent anD
P
arallel
O
PeratiOn
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
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.
Page 1 of 15
SMFL Rev K - 20101209
INTERPOINT [ INTERPOINT CORPORATION COMPANY ]
