1
SMFL SERIES
65 WATT
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
MODELS
VDC O
UTPUT
SINGLE
3.3
5
12
15
DUAL
5
12
15
Size (max.): 3.005 x 1.505 x 0.410 inches (76.33 x 38.23 x 10.41 mm)
See Figures 17 and 18 for dimensions. Case options V, W, Y, and
Z are available by special order. Please refer to our databook or
contact your Interpoint representative for more information.
Weight:
85 grams maximum
Screening: Space prototype, Class H, or Class K (MIL-PRF-38534)
Radiation hardness levels O or R
Available configurations: OO, HO, HR, KR
DESCRIPTION
The SMFL SeriesTM 28-volt DC/DC converters are rated up to 65
watts output power over a -55 to +125C 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 180 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.
S
CREENING AND
R
EPORTS
SMFL converters offer three screening options (Space prototype,
Class H, or Class K) and two levels of radiation hardness (O or R).
See Tables 1, 2, and 3 for more information. Detailed reports on
product performance are also available and are listed in Table 4.
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.
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
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.
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, 95% 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.
F
EATURES
Fully qualified to Class H or K
55 to +125C operation
16 to 40 VDC input
Fully Isolated
Magnetic feedback
Fixed frequency, 600 kHz typical
Topology Single Ended Forward
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 87% efficiency
Parallelable up to 180 watts
TYPICAL CHARACTERISTICS
SYNC AND INHIBIT (INH1, INH2)
RECOMMENDED OPERATING CONDITIONS
ABSOLUTE MAXIMUM RATINGS
Input Voltage
16 to 40 VDC
Power Dissipation (Pd)
14 watts (16 watts SMFL2805S, SMFL2805D)
Output Power
40 to 65 watts depending on model
Lead Soldering Temperature (10 sec per lead)
300C
Storage Temperature Range (Case)
65C to +150C
2
SMFL SERIES
65 WATT
DC/DC C
ONVERTERS
Output Voltage Temperature Coefficient
100 ppm/C typical
Input to Output Capacitance
150 pF, typical
Isolation
100 megohm minimum at 500 V
Audio Rejection
50 dB typical
Conversion Frequency
Free run mode 600 kHz typical
550 kHz. min, 650 kHz max
External sync range 525 to 675 kHz
Inhibit Pin Voltage (unit enabled)
INH1 = 9 to12 V, INH2 = 6 to 9 V
Input Voltage Range
16 to 40 VDC continuous
Case Operating Temperature (Tc)
55C to +125C full power
Sync In (525 to 675 kHz)
Duty cycle 40% min, 60% max
Logic low 0.8 V max
Logic high 4.5 V min, 9 V max
Referenced to input common
If not used, connect to input common
Sync Out
Referenced to input common
If not used, leave unconnected
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
If not used, leave unconnected
Notes
1. Unit will shut down above approximately 45V but will be undamaged and
will restart when voltage drops into normal range.
2. Indefinite short circuit protection not guaranteed above 125C case.
3. Recovery time is measured from application of the transient to point at
which Vout is within 1% of final value.
4. Guaranteed but not tested.
SINGLE OUTPUT MODELS
SMFL283R3S
SMFL2805S
SMFL2812S
SMFL2815S
PARAMETER
CONDITION
MIN TYP MAX
MIN TYP MAX
MIN
TYP MAX
MIN
TYP MAX
UNITS
OUTPUT VOLTAGE
Tc = 25C
3.27
3.3
3.33
4.95
5.00
5.05
11.88 12.00 12.12
14.85 15.00 15.15
VDC
OUTPUT CURRENT
V
IN
= 16 TO 40 VDC
0
--
12
0
--
10
0
--
5
0
--
4.33
A
OUTPUT POWER
V
IN
= 16 TO 40 VDC
0
--
40
0
--
50
0
--
60
0
--
65
W
OUTPUT RIPPLE
Tc = 25C
--
10
35
--
15
35
--
30
75
--
30
85
VOLTAGE 10 k - 2 MHz
Tc = 55C to +125C
--
10
50
--
30
50
--
45
100
--
45
110
mV p-p
LINE REGULATION
V
IN
= 16 to 40 VDC
--
0
20
--
0
20
--
0
20
--
0
20
mV
LOAD REGULATION
NO LOAD TO FULL
--
--
20
--
--
20
--
--
20
--
--
20
mV
INPUT VOLTAGE
CONTINUOUS
16
28
40
16
28
40
16
28
40
16
28
40
VDC
TRANSIENT
1, 4
50 ms
--
--
50
--
--
50
--
--
50
--
--
50
V
INPUT CURRENT
NO LOAD
--
70
100
--
70
120
--
50
80
--
50
80
mA
FULL LOAD
--
--
2.1
--
--
2.5
--
--
2.8
--
--
3.0
A
INHIBITED - INH1
--
9
14
--
9
14
--
9
14
--
9
14
mA
INHIBITED - INH2
--
35
70
--
35
70
--
35
70
--
35
70
INPUT RIPPLE
CURRENT
10 kHz - 10 MHz
--
15
50
--
15
50
--
15
50
--
15
50
mA pp
EFFICIENCY
Tc = 25C
70
--
--
75
80
--
81
86
--
82
87
--
%
LOAD FAULT
2
POWER DISSIPATION
SHORT CIRCUIT
Tc = 25C
--
12.5
14
--
12.5
16
--
10
14
--
10
14
W
RECOVERY
--
1.5
4
--
1.5
4
--
1.5
4
--
1.5
4
ms
STEP LOAD RESP.
50% 100% 50%
TRANSIENT
--
200
300
--
250
350
--
450
700
--
500
700
mV p
RECOVERY
3, 4
--
1.5
3.0
--
1.5
3.0
--
1.5
3.0
--
1.5
3.0
ms
STEP LINE RESP
3, 4
.
16 40 16 VDC
TRANSIENT
--
250
300
--
250
300
--
250
400
--
250
400
mV pk
RECOVERY
--
200
30
--
200
300
--
200
300
--
200
300
s
START-UP
DELAY
--
3.5
6
--
3.5
6
--
3.5
6
--
3.5
6
ms
OVERSHOOT
4
--
0
25
--
0
25
--
0
50
--
0
50
mV pk
PINS NOT USED
TR1, Master, and Slave
If not used, leave unconnected
Electrical Characteristics: 25C Tc, 28 VDC Vin, 100% load, radiation level O, unless otherwise specified.
3
SMFL SERIES
65 WATT
DC/DC C
ONVERTERS
DUAL OUTPUT MODELS
SMFL2805D
SMFL2812D
SMFL2815D
PARAMETER
CONDITIONS
MIN TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
OUTPUT VOLTAGE
Tc = 25C
+V
OUT
4.95
5.00
5.05
11.88 12.00
12.12 14.85 15.00
15.15
VDC
V
OUT
4.92
5.00
5.08
11.82 12.00
12.18
14.77 15.00
15.23
OUTPUT CURRENT
1
V
IN
= 16 TO 40 VDC
EACH OUTPUT
0
--
7
0
--
3.5
0
--
3.03
A
TOTAL OUTPUT
0
--
10
0
--
5
0
--
4.33
OUTPUT POWER
V
IN
= 16 TO 40 VDC
0
--
50
0
--
60
0
--
65
W
OUTPUT RIPPLE
VOLTAGE V
OUT
10 kHz - 2 MHz
--
50
100
--
50
120
--
50
150
mV p-p
LINE REGULATION
V
IN
= 16 TO 40 VDC
+V
OUT
--
0
50
--
0
50
--
0
50
mV
V
OUT
--
25
100
--
25
100
--
25
100
LOAD REGULATION
NO LOAD TO FULL
+V
OUT
--
0
50
--
10
100
--
10
100
mV
V
OUT
--
25
100
--
50
120
--
50
150
CROSS REGULATION
SEE NOTE 2
--
5
8
--
2
4
--
2
4
%
SEE NOTE 3
--
3
6
--
2
4
--
2
4
INPUT VOLTAGE
CONTINUOUS
16
28
40
16
28
40
16
28
40
VDC
TRANSIENT
4, 7
50 ms.
--
--
50
--
--
50
--
--
50
V
INPUT CURRENT
NO LOAD
--
50
120
--
50
100
--
50
100
mA
FULL LOAD
--
--
2.40
--
--
2.80
--
--
3.00
A
INHIBITED - INH1
--
9
14
--
9
14
--
9
14
mA
INHIBITED - INH2
--
35
70
--
35
70
--
35
70
INPUT RIPPLE
CURRENT
10 kHz - 10 MHz
--
15
50
--
15
50
--
15
50
mA p-p
EFFICIENCY
BALANCED LOAD
75
80
--
81
86
--
82
87
--
%
LOAD FAULT
5
POWER DISSIPATION
SHORT CIRCUIT
--
12.5
16
--
10
14
--
10
14
W
RECOVERY
--
1.5
4.0
--
1.5
4.0
--
1.5
4.0
ms
STEP LOAD
50 %100% 50% LOAD
RESPONSE V
OUT
TRANSIENT
--
250
350
--
450
600
--
500
600
mV pk
RECOVERY
6, 7
--
1.5
3.0
--
1.5
3.0
--
1.5
3.0
ms
STEP LINE
6, 7
16 40 16 V
IN
RESPONSE V
OUT
TRANSIENT
7
--
250
300
--
250
400
--
250
400
mV pk
RECOVERY
--
200
300
--
200
300
--
200
300
s
STARTUP
DELAY
--
3.5
6
--
3.5
6
--
3.5
6
ms
OVERSHOOT
7
--
0
25
--
0
50
--
0
50
mV pk
Notes
1. Up to 70% of the total output power is available from either output providing
the opposite output is simultaneously carrying 30% of the total power.
2. Effect on the negative output under the following conditions:
+P
out
30% to 70%; P
out
70% to 30%
3. Effect on the negative output under the following conditions:
+P
out
50%; P
out
10% to 50%
4. Unit will shut down above approximately 45V but will be undamaged and will
restart when voltage drops into normal range.
5. Indefinite short circuit protection not guaranteed above 125C case.
6. Recovery time is measured from application of the transient to point at which
Vout is within 1% of final value.
7. Guaranteed but not tested.
Electrical Characteristics: 25C Tc, 28 VDC Vin, 100% load, radiation level O, unless otherwise specified.
4
SMFL SERIES
65 WATT
DC/DC C
ONVERTERS
SINGLE OUTPUT MODELS CONNECTION DIAGRAMS - SENSE AND PARALLEL
RL
1
2
3
4
5
6
REMOTE SENSE CONNECTION
12
11
10
9
8
7
+
28V
+
Inhibit
Sync In
RL
1
2
3
4
5
6
OUTPUT VOLTAGE ADJUST CONNECTION
12
11
10
9
8
7
+
28V
+
Inhibit
Sync In
0.1
0.2
0.3
0.4
0.5
70
140
210
280
350
25
50
75
100
125
20
40
60
80
100
RA (OHMS)
5V
12V
15V
VOUT INCREASE
(VOLT)
RA
Positive Input
Input Common
TR1
INH1
Sync Out
Sync In
MSTR/INH2
Slave
Pos. Sense
Sense Return
Output Common
Positive Output
Positive Input
Input Common
TR1
INH1
Sync Out
Sync In
MSTR/INH2
Slave
Pos. Sense
Sense Return
Output Common
Positive Output
RL
1
Positive Input
Input Common
TR1
INH1
Sync Out
Sync In
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
CONNECT ONLY WHEN 2 SLAVES ARE USED
12
11
10
9
8
7
12
11
10
9
8
7
12
11
10
9
8
7
+
MSTR/INH2
Slave
Pos. Sense
Sense Return
Output Common
Positive Output
MASTER
SLAVE 1
SLAVE 2
28V
+
Inhibit
Sync In
Positive Input
Input Common
TR1
INH1
Sync Out
Sync In
MSTR/INH2
Slave
Pos. Sense
Sense Return
Output Common
Positive Output
Positive Input
Input Common
TR1
INH1
Sync Out
Sync In
MSTR/INH2
Slave
Pos. Sense
Sense Return
Output Common
Positive Output
F
IGURE
1: S
ENSE
C
ONNECTIONS AND
T
RIM
T
ABLE
F
IGURE
2: P
ARALLEL
C
ONNECTIONS
PIN OUT
SMFL 28 05 S / K R
Base Model
Input Voltage
Output Voltage
Screening
Number of Outputs
(S = single, D = dual)
Radiation Level
Angled corner indicates pin one.
1
2
3
4
5
6
12
11
10
9
8
7
TOP VIEW
SMFL
(Pin side, marked side)
5
SMFL SERIES
65 WATT
DC/DC C
ONVERTERS
MODEL NUMBERING KEY
Pin
Single Output
Dual Output
1
Positive Input
Positive Input
2
Input Common
Input Common
3
Triple (TRI)
Triple (TRI)
4
Inhibit 1 (INH1)
Inhibit 1 (INH1)
5
Sync Out
Sync Out
6
Sync In
Sync In
7
Positive Output
Positive Output
8
Output Common
Output Common
9
Sense Return
Negative Output
10
Positive Sense
No connection
11
Slave
Slave
12
Master / Inhibit 2 Master / Inhibit 2
Pin 6 should be connected to input common if
external sync (Sync In) is not used.
Sense pins must be connected to their respective
outputs if not used.
Typical Performance Curves: 25C Tc , 28 VDC Vin, 100% load, free run, unless otherwise specified.
Output (Watts)
SMFL2805S & SMFL2805D Efficiency
Efficiency (%)
60
90
85
80
75
70
10
20
30
40
50
28V
40V
65
16V
F
IGURE
4
Output Power (Watts)
SMFL2812S & SMFL2812D Efficiency
Efficiency (%)
60
90
85
80
75
70
10
20
30
40
50
60
40V
16V
28V
65
F
IGURE
5
F
IGURE
6
60
90
85
80
75
70
10
20
30
40
50
65
60
65
16V
Output Power (Watts)
SMFL2815S & SMFL2815D Efficiency
Efficiency (%)
40V
28V
See Figures 17 and 18 for dimensions.
F
IGURE
3: P
IN
O
UT
SMD NUMBERS
S
TANDARD
M
ICROCIRCUIT
D
RAWING
(SMD)
IN PROCESS
5962-9316302HXC
IN PROCESS
IN PROCESS
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
PDF 
ZIP