Crane Aerospace & Electronics Power Solutions
SMFL Single and Dual DC/DC Converters
28 VOLT INPUT – 65 WATT
F
EATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Fully qualified to Class H or K
–55° to +125°C operation
16 to 40 VDC input
Fully Isolated
Magnetic feedback
Fixed frequency, 600 kHz typical
Topology – Single Ended Forward
50 V for up to 120 ms transient protection
Inhibit input side and output side
Sync function
Output trim on single output models
Indefinite short circuit protection
Remote sense on single output models
Up to 85% efficiency / 43 W/in
3
Parallelable up to 148 watts
MODELS
VDC O
UTPUT
SINGLE
3.3
5
12
15
DUAL
±5
±12
±15
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 45 watts per cubic inch.
I
NHIBIT
The SMFL Series converters have two TTL compatible inhibit termi-
nals (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 open collector TTL compatible low (<0.8 volts)
is required to inhibit the converter between INH1 (pin 4) and Input
Common (pin 2). An open collector TTL compatible 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.
S
CREENING
SMFL converters offer screening options to Space Prototype (O),
Class H, or Class K. Available radiation hardness (RHA) levels are
O or R. See “Class H and K, QML Screening” tables for more infor-
mation.
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.
D
ESIGN
F
EATURES
The 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 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 specific output voltage by adding an external resistor.
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 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.
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
Electronics Group (Interpoint Brand)
PO Box 97005 • Redmond WA 98073-9705
425.882.3100 • electronics@craneae.com
www.craneae.com
Page 1 of 13
Rev G - 20060601
Crane Aerospace & Electronics Power Solutions
SMFL Single and Dual DC/DC Converters
28 VOLT INPUT – 65 WATT
OPERATING CONDITIONS AND CHARACTERISTICS
Input Voltage Range
• 16 to 40 VDC continuous
• 50 V for 120 ms transient
Output Power
• 40 to 65 watts depending on model
Lead Soldering Temperature (10 sec per lead)
• 300°C
Storage Temperature Range (Case)
• –65°C to +150°C
Power Dissipation (Pd)
• 14 watts (16 watts SMFL2805S, SMFL2805D)
Case Operating Temperature (Tc)
• –55°C to +125°C full power
Derate Output Power/Current
• MFL283R3S: linearly from 100% at 100 °C to 80% at 125 °C
Output Voltage Temperature Coefficient
• 100 ppm/°C typical
Input to Output Capacitance
• 150 pF, typical
Current Limit
• 125% of full load typical
Isolation
• 100 megohm minimum at 500 V
Audio Rejection
• 50 dB typical
Conversion Frequency (-55°C to 125°C)
• Free run mode 600 kHz typical
525 kHz. min, 675 kHz max
Inhibit Pin Voltage (unit enabled)
• INH1 = 9 to12 V, INH2 = 6 to 9 V
SYNC IN AND INHIBIT (INH1, INH2)
Sync In (525 to 675 kHz)
• Duty cycle 40% min, 60% max
• Logic low 0.8 V max
• Logic high 4.5 V min, 5 V max
• Referenced to input common
Sync Out
• Referenced to input common
Inhibit (INH1, INH2) TTL Open Collector
• Logic low (output disabled)
INH1 referenced to input common
Logic low 0.8 V max
Inhibit pin current 10 mA max
INH2 referenced to output common
Logic low 0.5 V max
Inhibit pin current 5 mA max
• Logic high (output enabled)
Open collector
MECHANICAL AND ENVIRONMENTAL
Size (maximum)
3.005 x 1.505 x 0.400 inches (76.33 x 38.23 x 10.16 mm)
See case U for dimensions.
Case options V, W, Y, and Z are available by special order.
Weight (maximum)
86 grams
Screening
Space Prototype, Class H, or Class K
Radiation hardness levels O or R
See “Class H and K, QML Screening” tables for more information.
Available configurations: OO, HO, HR, KR
www.craneae.com
Page 2 of 13
Rev G - 200600601
Crane Aerospace & Electronics Power Solutions
SMFL Single and Dual DC/DC Converters
28 VOLT INPUT – 65 WATT
MODEL NUMBERING KEY
Base Model
Input Voltage
Output Voltage
Number of Outputs
(S =
single,
D = dual)
Screening
Radiation Level
SMFL
28 05
S
/ K
R
SMD NUMBERS
S
TANDARD
M
ICROCIRCUIT
D
RAWING
(SMD)
IN PROCESS
5962-9316302HXC
5962-9316202HXC
5962-9316102HXC
IN PROCESS
IN PROCESS
5962-9319302HXC
SMFL S
ERIES
S
IMILAR
P
ART
SMFL283R3S/HO
SMFL2805S/HO
SMFL2812S/HO
SMFL2815S/HO
SMFL2805D/HO
SMFL2812D/HO
SMFL2815D/HO
The SMD number shown is for Class H screening, non-
flanged, and no Radiation Hardness Assurance (RHA) level.
See the SMD for the numbers for other screening and radia-
tion levels. For exact specifications for an SMD product, refer
to the SMD drawing. Call your Interpoint representative for
status on the SMFL SMD releases which are “in process.”
SMDs can be downloaded from
http://www.dscc.dla.mil/programs/smcr
Model Selection
SMFL28
Base model
Vout value
number of outputs
case option
screening
Choose one from each of the following rows
Vout value
Number of outputs
Case option
Screening
for singles 3R3, 5, 12, 15
“R” = decimal point, 3R3 = 3.3VDC
for duals: 5, 12, 15
S (single) or D (dual)
standard (case U, leave blank), V, W, Y, and Z available by special order.
OO - Space prototype, HO, HR, KR
www.craneae.com
Page 5 of 13
Rev G - 200600601
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