F
EATURES
•
•
•
•
•
•
•
•
•
•
•
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Fully qualified to Class H or K
Radiation hardened
–55° to +125°C operation
16 to 40 VDC input
Fully isolated
Optocoupler feedback
Fixed frequency, 550 kHz typical
Topology – Single Ended Flyback
Inhibit function
Indefinite short circuit protection
5 watts output power
Up to 76% efficiency
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
SMSA SERIES
5 WATT
MODELS
VDC O
UTPUT
SINGLE
DUAL
3.3
±5
5
±12
12
±15
15
Size (max.): 1.075 x 1.075 x 0.270 inches
(27.31 x 27.31 x 6.86 mm)
See Figures 23 and 24 for dimensions.
Weight:
15 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 SMSA Series™ of high frequency DC/DC converters offers a
new standard of performance for low power, space qualified DC/DC
converters. SMSA converters provide up to 5 watts output power
over the full military temperature range of –55°C to +125°C with up
to 76% efficiency. Thick-film hybrid techniques provide military/aero-
space reliability levels and optimum miniaturization. The hermeti-
cally sealed case is only 1.075 by 1.075 inches — with a height of
only 0.270 inches. Power density for the SMSA Series converters is
16 watts per cubic inch. The SMSA Series’ small size, light weight,
and hermetically sealed metal packages make them ideal for use in
space, military, aerospace and other high reliability applications.
W
IDE
V
OLTAGE
R
ANGE
The SMSA converters are designed to provide full power operation
over the full 16 to 40 VDC voltage range. An undervoltage lockout
feature keeps the converter shutdown below approximately 13 VDC
to ensure smooth initialization.
I
MPROVED
D
YNAMIC
R
ESPONSE
The SMSA feed-forward compensation system provides excellent
dynamic response and noise rejection. Audio rejection is typically 50
dB. The minimum to maximum step line transient response is typi-
cally less than 1%.
S
CREENING AND
R
EPORTS
SMSA converters offer three screening options – Space prototype
Class H, or Class K – and two levels of radiation hardness. See
Tables 1 through 3 for more information. Detailed reports on product
performance are also available and are listed in Table 4.
I
NHIBIT
F
UNCTION
SMSA converters provide a TTL open collector-compatible inhibit
feature that can be used to disable internal switching and inhibit the
unit’s output. Inhibiting in this manner results in low standby current,
and no generation of switching noise.
The converter is inhibited when the TTL compatible low (≤0.8V) is
applied to the inhibit pin. The unit is enabled when the pin, which is
internally connected to a pull-up resistor, is left unconnected or is
connected to an open collector gate. The open circuit output voltage
associated with the inhibit pin is 9 to 11 VDC. In the inhibit mode, a
maximum of 4 mA must be sunk from the inhibit pin at 28 VDC input.
C
ONVERTER
D
ESIGN
The SMSA converters are switching regulators that use a flyback
converter design with a constant switching frequency of 550 kHz.
They are regulated, isolated units using a pulse width modulated
topology and built as high reliability thick-film hybrids. Isolation
between input and output circuits is provided with a transformer in
the forward power loop and an optical link in the feedback control
loop. Excellent input line transient response and audio rejection is
achieved by an advanced feed-forward compensation technique.
Negative output regulation is maintained by tightly coupled
magnetics. Predictable current limit is accomplished by direct moni-
toring of the output load current, which results in a constant current
output above the overload point. Internal input and output filters
eliminate the need for external capacitors.
®
45
SMSA SERIES
5 WATT
ABSOLUTE MAXIMUM RATINGS
Input Voltage
• 16 to 40 V
Output Power
• 5 watts
Lead Soldering Temperature (10 sec per lead)
• 300°C
Storage Temperature Range (Case)
• –65°C to +135°C
DC/DC C
ONVERTERS
INHIBIT
Inhibit TTL Open Collector
• Logic low (output disabled)
Logic low voltage
≤0.8
V max
Inhibit pin current 4 mA max
• Referenced to input common
• Logic high (output enabled)
Open collector
TYPICAL CHARACTERISTICS
Output Voltage Temperature Coefficient
• 100 ppm/°C typical
Input to Output Capacitance
• 50 pF typical
Isolation
• 100 megohm minimum at 500 V
Audio Rejection
• 50 dB typical
Conversion Frequency
• 550 kHz typical
450 kHz min, 600 kHz max
Inhibit Pin Voltage (unit enabled)
• 9 to 11 V
RECOMMENDED OPERATING CONDITIONS
Input Voltage Range
• 16 to 40 VDC continuous
• 50 V for up to 50 msec transient
Case Operating Temperature (Tc)
• –55°C to +125°C full power
• –55°C to +135°C absolute
Derating Output Power/Current (Tc)
• Linearly from 100% at 125°C to 0% at 135°C
Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, radiation level O, unless otherwise specified.
SINGLE OUTPUT MODELS
PARAMETER
CONDITIONS
OUTPUT VOLTAGE
Tc = –55°C TO +125°C
OUTPUT CURRENT
Tc = –55°C TO +125°C
V
IN
= 16 TO 40 VDC
OUTPUT POWER
OUTPUT RIPPLE
VOLTAGE
LINE REGULATION
LOAD REGULATION
INPUT VOLTAGE
V
IN
= 16 TO 40 VDC
Tc = –55°C TO +125°C
10 kHz - 2 MHz
V
IN
= 16 TO 40 VDC
Tc = –55°C TO +125°C
NO LOAD TO FULL
Tc = –55°C TO +125°C
Tc = –55°C TO +125°C
NO LOAD TO FULL
CONTINUOUS
TRANSIENT
3
50 ms
NO LOAD
FULL LOAD
INHIBITED
10 kHz - 10 MHz
Tc = –55°C TO +125°C
POWER DISSIPATION
RECOVERY
50% - 100% - 50%
TRANSIENT
RECOVERY
2, 3
TRANSIENT
16 TO 40 V
IN
40 TO 16 V
IN
RECOVERY
16 TO 40 V
IN
40 TO 16 V
IN
START-UP
DELAY
OVERSHOOT
3
—
—
—
—
—
300
10
10
4
600
50
50
—
—
—
—
—
150
10
10
5
450
50
50
—
—
—
—
—
125
10
10
5
500
50
50
—
—
—
—
—
150
10
10
5
600
50
50
W
mV p-p
mV
mV
SMSA283R3S
MIN TYP MAX
3.25 3.30 3.35
0
—
1200
SMSA2805S
MIN TYP MAX
4.95 5.00 5.05
0
—
1000
SMSA2812S
MIN TYP MAX
11.88 12.00 12.12
0
—
417
SMSA2815S
MIN TYP MAX
14.85 15.00 15.15
0
—
333
UNITS
VDC
mA
INPUT CURRENT
INPUT RIPPLE
CURRENT
EFFICIENCY
LOAD FAULT
1, 2
SHORT CIRCUIT
STEP LOAD
RESPONSE
STEP LINE
RESPONSE
2, 3
16
0
—
—
—
—
—
60
—
—
—
—
—
—
—
—
—
—
28
—
35
250
3
50
60
—
1.5
12.5
200
200
200
200
400
400
10
0
40
50
60
—
5
200
300
—
2.4
25
500
500
500
500
1000
1000
75
200
16
0
—
—
—
—
—
68
—
—
—
—
—
—
—
—
—
—
28
—
35
250
3
50
60
74
1.5
12.5
200
200
200
200
400
400
10
0
40
50
60
—
5
200
300
—
2.0
25
500
500
500
500
1000
1000
75
200
16
0
—
—
—
—
—
69
—
—
—
—
—
—
—
—
—
—
28
—
35
235
3
50
60
74
1.2
1
300
400
200
250
700
700
10
0
40
50
60
—
5
200
300
—
1.9
10
750
1000
800
600
1300
1300
75
500
16
0
—
—
—
—
—
%
—
—
—
—
—
—
—
—
—
—
28
—
35
235
3
50
60
1.2
1
400
400
200
200
500
500
10
0
40
50
60
—
5
200
300
1.8
10
1000
1000
500
500
1300
1300
75
500
VDC
V
mA
mA p-p
W
ms
mV pk
µs
mV pk
µs
ms
mV pk
Notes
1. Indefinite short circuit protection not guaranteed above 125°C (case).
2. Recovery time is measured from application of the transient to point at which
V
OUT
is within 1% of V
OUT
at final value.
3. Guaranteed but not tested.
®
46
DC/DC C
ONVERTERS
DUAL OUTPUT MODELS
PARAMETER
OUTPUT VOLTAGE
OUTPUT CURRENT
1
OUTPUT POWER
1
OUTPUT RIPPLE VOLT.
LINE REGULATION
CONDITIONS
+V
OUT
–V
OUT
V
IN
= 16 to 40 VDC
Tc = –55°C to +125°C
V
IN
= 16 to 40 VDC
Tc = –55°C to +125°C
10 kHz - 2 MHz
Vin = 16 to 40 VDC
Tc = –55°C to +125°C
+V
OUT
–V
OUT
LOAD REGULATION
NO LOAD TO FULL
Tc = –55°C to +125°C
+V
OUT
–V
OUT
CROSS REGULATION
2
INPUT VOLTAGE
+P
O
= 30 - 70 %, –P
O
=70 - 30%
–P
O
= 30 - 70 %, +P
O
= 70 - 30%
NO LOAD TO FULL
CONTINUOUS
TRANSIENT
5
50 msec
NO LOAD
FULL LOAD
INPUT RIPPLE
CURRENT
EFFICIENCY
LOAD FAULT
3, 4
INHIBITED
10 kHz TO 10 MHz
Tc = –55°C to +125°C
POWER DISSIPATION
SHORT CIRCUIT
RECOVERY
50% - 100% - 50% BALANCED
TRANSIENT
RECOVERY
4, 5
STEP LINE RESP.
4, 5
TRANSIENT
RECOVERY
START-UP
16 TO 40 VDC
40 TO 16 VDC
—
—
—
10
100
5
120
400
8
—
—
—
10
100
3.7
120
400
6
—
—
—
—
—
20
40
100
200
—
—
20
40
100
200
—
—
MIN
4.95
4.9
—
—
—
SMSA 2805D
TYP
5.00
5.0
±500
—
—
MAX
5.05
5.1
800
5
300
SMSA2812D
MIN
11.88
11.76
—
—
—
TYP
12.00
12.00
±208
—
80
MAX
12.12
12.24
333
5
300
SMSA SERIES
5 WATT
SMSA2815D
MIN
14.85
14.70
—
—
—
TYP
15.00
15.00
±167
—
120
MAX
15.15
15.30
267
5
300
mA
W
mV p-p
UNITS
VDC
Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, radiation level O, unless otherwise specified.
10
40
50
180
mV
10
50
3
50
200
6
mV
%
16
—
—
—
—
—
—
65
—
—
—
—
—
—
—
—
—
—
28
—
30
248
3
50
60
70
1.3
—
±200
200
±200
±200
300
800
10
0
40
50
50
—
5
200
300
—
2.1
50
±550
500
±500
±500
750
2000
30
500
16
—
—
—
—
—
—
67
—
—
—
—
—
—
—
—
—
—
28
—
40
235
3
50
60
73
1.3
1
±200
200
±200
±200
300
800
10
0
40
50
63
—
5
200
300
—
1.7
30
±550
500
±500
±500
750
2000
30
500
16
—
—
—
—
—
—
68
—
—
—
—
—
—
—
—
—
—
28
—
38
235
3
50
60
73
1.3
1
±220
200
±600
±600
500
500
10
0
40
50
60
—
5
200
300
—
1.6
50
±600
500
±1500
±1500
1200
1200
25
500
VDC
V
mA
INPUT CURRENT
mA p-p
%
W
ms
mV
µs
mV pk
µs
ms
mV pk
STEP LOAD
RESPONSE
16 TO 40 VDC
40 TO 16 VDC
DELAY
OVERSHOOT
5
Notes
1. Up to 4 watts (80% of full power) is available from either output providing the
opposite output is carrying 20% of total power.
2. Shows regulation effect on the minus output during the defined cross loading
conditions, with 80% and 20% referring to the total output power of the
converter. See Figures 15 and 16.
3. Indefinite short circuit protection not guaranteed above 125°C (case).
4. Recovery time is measured from application of the transient to point at which
V
OUT
is within 1% of V
OUT
at final value.
5. Guaranteed but not tested.
®
47
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