Crane Aerospace & Electronics Power Solutions
sMFL sꢀꢁglꢂ ꢃꢁꢄ dꢅꢃl dc/dc cꢆꢁvꢂꢇꢈꢂꢇꢉ
28 VoLt input – 65 Watt
Features
•ꢀ FullyꢀqualifiedꢀtoꢀClassꢀHꢀorꢀK
•ꢀ -55°ꢀtoꢀ+125°Cꢀoperation
•ꢀ 16ꢀtoꢀ40ꢀVDCꢀinput
•ꢀ FullyꢀIsolated
•ꢀ Magneticꢀfeedback
•ꢀ Fixedꢀfrequency,ꢀ600ꢀkHzꢀtypical
•ꢀ Topologyꢀ–ꢀSingleꢀEndedꢀForward
•ꢀ 50ꢀVꢀforꢀupꢀtoꢀ120ꢀmsꢀtransientꢀprotection
•ꢀ Inhibitꢀinputꢀsideꢀandꢀoutputꢀside
•ꢀ Syncꢀfunction
MODELS
VDC Ou t p u t
SINꢀLE
3.3
5
DUꢁꢂ
±5
±12
±15
•ꢀ Outputꢀtrimꢀonꢀsingleꢀoutputꢀmodels
•ꢀ Indefiniteꢀshortꢀcircuitꢀprotection
•ꢀ Remoteꢀsenseꢀonꢀsingleꢀoutputꢀmodels
12
15
3
•ꢀ Upꢀtoꢀ85%ꢀefficiencyꢀ/ꢀ43ꢀW/in
•ꢀ Parallelableꢀupꢀtoꢀ148ꢀwatts
specific output voltage by adding an external resistor (see Figure 1
for resistor values).
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 paralleled 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.
in h i b i t
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. A logic low (<0.8 volts) is required to inhibit the converter
between INH1 (pin 4) and Input Common (pin 2). A logic low (<0.5
volts) is required to inhibit the converter between INH2 (pin 12) and
Output Common (pin 8). The application of intermediate voltages to
these pins (1.5 to 10.5 volts) should be avoided.
Sc r e e n i n g
SMFL converters offer the following screening options: Space
Prototype (O), Class H, or Class K. Radiation tolerant to Radiation
Hardness Assurance (RHA) levels of “-” (O) or “R”, per MIL-STD-
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 “Class H
and K, MIL-PRF-38534 Screening” tables for more information.
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”).
De S i g n Fe a t u r e S
cu r r e n t a n D Pa r a l l e l OP e r a t i O n
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.
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 sharing mode,
one SMFL converter is designated as a master. The SLAVE pin (pin
11) of the master is left unconnected and the MSTR/INH2 pin (pin
12) of the master is connected to the SLAVE pin (pin 11) of the slave
units. The units designated as slaves have the MSTR/INH2 pin (pin
12) connected to the SNS RTN pin (pin 9). Note that synchronizing
the units together is not required for current sharing operation. A
second slave unit may be placed in parallel with a master and slave;
this requires the TRI pin (pin 3) of the master unit to be connected to
the SNS RTN pin (pin 9). See Figure 2 for a block diagram of parallel
connections.
Isolation between input and output circuits is provided with a trans-
former 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 feed-
back 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 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 regula-
tion is achieved through a wide-bandwidth magnetic feedback circuit.
The output voltage on single SMFL models can be trimmed to a
When paralleled, 76% of the total combined power ratings of the
SMFL converters are available at the load. Overload and short circuit
performance are not adversely affected during parallel operation.
Crane Aerospace & Electronics
Page 1 of 13
Electronics ꢀroup (Interpoint Brand)
POꢀBoxꢀ97005ꢀꢀ•ꢀꢀRedmondꢀWꢁꢀ98073-9705
425.882.3100ꢀꢀꢀ•ꢀꢀꢀelectronics@craneae.com
www.craneae.com
Rev H - 20071102
ClearedꢀbyꢀU.S.ꢀDoDꢀOSRꢀforꢀPublicꢀReleaseꢀ
OSR case number 09S-0995, dated March 13, 2009.
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