F
EATURES
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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
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
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
SMFL SERIES
65 WATT
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
I
NHIBIT
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 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.
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 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.
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, 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.
1
SMFL SERIES
65 WATT
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)
• 300°C
Storage Temperature Range (Case)
• –65°C to +150°C
DC/DC C
ONVERTERS
SYNC 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, 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
TYPICAL CHARACTERISTICS
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
RECOMMENDED OPERATING CONDITIONS
Input Voltage Range
• 16 to 40 VDC continuous
Case Operating Temperature (Tc)
• –55°C to +125°C full power
PINS NOT USED
TR1, Master, and Slave
If not used, leave unconnected
Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, radiation level O, unless otherwise specified.
SINGLE OUTPUT MODELS
PARAMETER
OUTPUT VOLTAGE
OUTPUT CURRENT
OUTPUT POWER
OUTPUT RIPPLE
VOLTAGE 10 k - 2 MHz
LINE REGULATION
LOAD REGULATION
INPUT VOLTAGE
INPUT CURRENT
CONDITION
Tc = 25°C
V
IN
= 16 TO 40 VDC
V
IN
= 16 TO 40 VDC
Tc = 25°C
Tc = –55°C to +125°C
V
IN
= 16 to 40 VDC
NO LOAD TO FULL
CONTINUOUS
TRANSIENT
1, 4
50 ms
NO LOAD
FULL LOAD
INHIBITED - INH1
INHIBITED - INH2
INPUT RIPPLE
CURRENT
EFFICIENCY
LOAD FAULT
2
10 kHz - 10 MHz
Tc = 25°C
POWER DISSIPATION
SHORT CIRCUIT
Tc = 25°C
RECOVERY
STEP LOAD RESP.
50% – 100% – 50%
TRANSIENT
RECOVERY
3, 4
16 – 40 – 16 VDC
TRANSIENT
RECOVERY
DELAY
OVERSHOOT
4
SMFL283R3S
MIN
3.27
0
0
—
—
—
—
16
—
—
—
—
—
—
70
TYP MAX
3.3 3.33
—
—
10
10
0
—
28
—
70
—
9
35
15
—
12
40
35
50
20
20
40
50
100
2.1
14
70
50
—
SMFL2805S
MIN
4.95
0
0
—
—
—
—
16
—
—
—
—
—
—
75
TYP MAX
5.00 5.05
—
—
15
30
0
—
28
—
70
—
9
35
15
80
10
50
35
50
20
20
40
50
120
2.5
14
70
50
—
SMFL2812S
MIN TYP MAX
11.88 12.00 12.12
0
0
—
—
—
—
16
—
—
—
—
—
—
81
—
—
30
45
0
—
28
—
50
—
9
35
15
86
5
60
75
100
20
20
40
50
80
2.8
14
70
50
—
SMFL2815S
MIN TYP MAX
14.85 15.00 15.15
0
0
—
—
—
—
16
—
—
—
—
—
—
82
—
—
30
45
0
—
28
—
50
—
9
35
15
87
4.33
65
85
110
20
20
40
50
80
3.0
14
70
50
—
mA pp
%
UNITS
VDC
A
W
mV p-p
mV
mV
VDC
V
mA
A
mA
—
—
—
—
—
—
—
—
12.5
1.5
200
1.5
250
200
3.5
0
14
4
300
3.0
300
30
6
25
—
—
—
—
—
—
—
—
12.5
1.5
250
1.5
250
200
3.5
0
16
4
350
3.0
300
300
6
25
—
—
—
—
—
—
—
—
10
1.5
450
1.5
250
200
3.5
0
14
4
700
3.0
400
300
6
50
—
—
—
—
—
—
—
—
10
1.5
500
1.5
250
200
3.5
0
14
4
700
3.0
400
300
6
50
W
ms
mV p
ms
mV pk
µs
ms
mV pk
STEP LINE RESP
3, 4
.
START-UP
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 125°C 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.
2
DC/DC C
ONVERTERS
PIN OUT
Pin
1
2
3
4
5
6
7
8
9
10
11
12
Single Output
Positive Input
Input Common
Triple (TRI)
Inhibit 1 (INH1)
Sync Out
Sync In
Positive Output
Output Common
Sense Return
Positive Sense
Slave
Master / Inhibit 2
Dual Output
Positive Input
Input Common
Triple (TRI)
Inhibit 1 (INH1)
Sync Out
Sync In
Positive Output
Output Common
Negative Output
No connection
Slave
Master / Inhibit 2
Angled corner indicates pin one.
SMFL SERIES
65 WATT
1
2
3
4
5
6
12
11
TOP VIEW
SMFL
(Pin side, marked side)
10
9
8
7
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.
See Figures 17 and 18 for dimensions.
F
IGURE
3: P
IN
O
UT
SMD NUMBERS
S
TANDARD
M
ICROCIRCUIT
D
RAWING
(SMD)
SMFL S
ERIES
S
IMILAR
P
ART
SMFL283R3S/HO
SMFL2805S/HO
SMFL2812S/HO
SMFL2815S/HO
SMFL2805D/HO
SMFL2812D/HO
SMFL2815D/HO
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
IN PROCESS
5962-9316302HXC
IN PROCESS
IN PROCESS
IN PROCESS
IN PROCESS
5962-9319302HXC
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
Typical Performance Curves: 25°C Tc , 28 VDC Vin, 100% load, free run, unless otherwise specified.
90
85
16V
90
85
16V
90
85
16V
Efficiency (%)
Efficiency (%)
Efficiency (%)
80
75
28V
80
75
70
65
28V
80
75
70
65
40V
28V
40V
70
65
60
10
20
30
40
50
40V
Output (Watts)
60
10
20
30
40
50
60
60
10
20
30
40
50
60 65
Output Power (Watts)
Output Power (Watts)
SMFL2805S & SMFL2805D Efficiency
SMFL2812S & SMFL2812D Efficiency
SMFL2815S & SMFL2815D Efficiency
F
IGURE
4
F
IGURE
5
F
IGURE
6
5
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