PD-97812C
LSO SERIES
HYBRID-HIGH RELIABILITY
RADIATION HARDENED
DC-DC CONVERTER
28V Input, Single/Dual Output
LSO
Description
The LSO Series of DC-DC converters are, high reliability
devices designed for hostile radiation hardened
environments. The design is based on the heritage-rich
LS Series with enhanced functional performance and an
inclusion of an output overvoltage protection. The LSO
Series provide up to 30 watts output power, small size,
low weight, integrated EMI filtering and a high tolerance
to environmental stresses such as radiation, temperature
extremes, mechanical shock, and vibration. All
components are fully de-rated to meet the requirements
of MIL-STD-1547, MIL-STD-975 and NASA EEE-INST-
002. Extensive documentation including, thermal
analysis, stress analysis and reliability predictions are
available.
The LSO Series of converters incorporate a fixed
frequency single forward topology with magnetic
feedback and an internal EMI filter. These converters are
capable of meeting the conducted emissions
requirements of MIL-STD-461C without any additional
components. All models include an external inhibit port
and have an adjustable output voltage. The converters
are overload, short circuit and output over-voltage
protected. They are enclosed in a hermetic 3.5" x 2.5" x
0.475" H steel package and weigh less than 125 grams.
The package utilizes rugged ceramic feed-through
copper core pins and is sealed using parallel seam
welding.
Manufactured in a facility fully qualified to MIL-PRF-
38534, these converters are fabricated utilizing DLA
qualified processes. For available screening options,
refer to device screening table in the data sheet.
Variations in electrical specifications and screening to
meet custom requirements can be accommodated.
Features
18 to 40V DC Input Range
Total Ionization Dose > 100 kRad(Si)
SEE Hardened to LET (Heavy Ions) up to
82 MeVcm
2
/mg (SEU, SEL, SEGB, SEGR)
Internal EMI filter; Converter Capable of
meeting MIL-STD-461C CE03
Derated per MIL-STD-1547, MIL-STD-975 and
NASA EEE-INST-002
Magnetically Coupled Feedback
Up to 30W Output Power
Single and Dual Output Models Include
1.5, 1.8, 2.5, 3.3, 5, 12, 15, ±5, ±12 and ±15V
Remote Sense Compensation for Single Output
Latch-off Output Overvoltage Protection
Input Current Telemetry
Input Under voltage Lockout with Latching Mode
Options
High Efficiency - to 81%
20M @ 100V
DC
Isolation
Under voltage Protection
Short Circuit and Overload Protection
Adjustable Output Voltage
Adjustable External OVP-115% to 125%
External Inhibit
Low Weight, < 125 grams
4000000 Hour MTBF (SF)
Applications
Geo Synchronous Satellite
Low Earth Orbit
Deep Space Probe
Communication and Display Systems
Payload and Experiment LVPS
1
International Rectifier HiRel Products, Inc.
2020-07-28
(28V Input, Single/Dual Output)
Circuit Description
The LSO Series converters utilize a single-ended forward
topology with resonant reset. The nominal switching
frequency is 500kHz. Electrical isolation and tight output
regulation are achieved through the use of a magnetically
coupled feedback. Voltage feed-forward with duty factor
limiting provides high line rejection.
An internal EMI filter allows the converter to meet the
conducted emissions requirements of MIL-STD-461C on
the input power leads.
LSO SERIES
Functional Notes
Input Current Telemetry:
The LSO Series single and
dual output models also feature an input current telemetry
with a magnitude of 0 to 3.3V full scale. The voltage signal
at this pin (Pin 7) with respect to Output Return (Pin 12) is
equal to 1.5 times the input current (Vin TLM (V) =1.5
*Input Current (A)+/-0.1V)
Short Circuit and Overload Protection:
Output current
is limited under any load fault condition to approximately
125% of rated. An overload condition causes the converter
output voltage to drop below nominal. The converter will
resume normal operation when the load current is reduced
below the current limit point. This protects the converter
from both overload and short circuit conditions. The
current limit point exhibits a slightly negative temperature
coefficient to reduce the possibility of thermal runaway.
Input Under voltage Lockout (UVLO) and Under
voltage Release (UVR):
The converter is designed to
be protected against an under voltage condition. The
converter will be in a non-functional (UVLO) mode when
the input voltage is approximately 15.5V or less. The
converter will turn on when the input voltage rises to 15.5V
to 17.9V (defined as UVR threshold) and will provide a
regulated output as the input voltage reaches 18V.
Should the input voltage drops below 16.5V to 14.5V
(defined as UVLO threshold), the converter will turn off
and remains off so long as the input voltage remains
under the UVLO threshold. The converter will resume a
normal operation when the input line rises above the UVR
threshold. However, the converter can be configured to
remain in a latch-up mode if desired.
To take advantage of the latch-up feature, the U/V Latch
Pin (Pin 5) should be shorted (with less than 100 Ohms) to
the Inhibit Return Pin (Pin 4). Note that in this mode the
converter will latch off if an under voltage condition lasts
more than 1milli-sec. The converter is reset by a shorted
Enable Input pin command followed by an open Enable
Input pin command.
Output Overvoltage Protection:
The converter also
features an output over-voltage protection. One OVP
circuitry for each output for the dual output models. In an
event the voltage output exceeds a preset voltage
threshold of approximately 120 +/- 5% of nominal voltage
output, the converter will turn off. The input power to the
converter or the signal at the Inhibit pin must be recycled
(connecting and removing the Inhibit pin to/from Inhibit
Return pin) to turn on the converter. This event is possible
only if the converter shuts off due to a false triggering. The
OVP threshold voltage can also be reset to within 115% to
125% of nominal output voltage with two external
resistors. Refer to the Application Notes section of the
data sheet on page 9.
Inhibit (On/Off Command):
An external inhibit port is
provided to control converter operation. The converter’s
operation is inhibited when this pin is pulled low. It is
intended to be driven by an open collector logic device.
The pin may be left open for normal operation and has a
nominal open circuit voltage of 4V with respect to the
inhibit return (Pin 4).
Output Voltage Adjustment:
The output voltage of all
models can be adjusted greater or less than the nominal
output voltage using a single external resistor. Refer to the
Application Notes section of the data sheet on page 9.
Design Methodology
The LSO Series was developed using a proven
conservative design methodology derived from other
space level designs that includes selection of established
reliability components and fully de-rating to the
requirements of MIL-STD-1547, MIL-PRF-975 and NASA
EEE-INST-002 except for the CDR type ceramic
capacitors, a capacitor with 50V rating is used for in-circuit
voltage stress of less than 10V. A magnetic feedback
circuit is utilized instead of opto couplers to minimize
temperature, aging and radiation sensitivity. PSPICE was
used extensively to predict and optimize circuit
performance for both beginning and end-of-life. Thorough
design analyses include stress, thermal, and reliability
(MTBF).
2
International Rectifier HiRel Products, Inc.
2020-07-28
(28V Input, Single/Dual Output)
Specifications
Absolute Maximum Ratings
Input Voltage range
Output power
Lead Temperature
Operating Case temperature
Storage temperature
-0.5V
DC
to +60V
DC
Internally limited
+300°C for 10 seconds
-55°C to +125°C (Note 13)
-55°C to +135°C
Recommended Operating Conditions
Input Voltage range
1
+18V
DC
to +40V
DC
Output power
0 to Max. Rated
Operating case temperature
-55°C to +85°C
Operating case temperature
-55°C to +70°C
LSO SERIES
1. Meets MIL-STD-1547, MIL-STD-975 and NASA EEE-INST-002
up to the input voltage at 38.6V.
Electrical Performance Characteristics
Parameter
Group A
Subgroup
Conditions
-55°C
T
C
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
Limits
Min
18
Nom
28
Max
40
Unit
Input Voltage
Output Voltage (V
OUT
)
LSO2801R5S
LSO2801R8S
LSO2802R5S
LSO2803R3S
LSO2805S
LSO2812S
LSO2815S
LSO2805D
LSO2812D
LSO2815D
LSO2801R5S
LSO2801R8S
LSO2802R5S
LSO2803R3S
LSO2805S
LSO2812S
LSO2815S
LSO2805D
LSO2812D
LSO2815D
Output power (P
OUT
)
LSO2801R5S
LSO2801R8S
LSO2802R5S
LSO2803R3S
All Others
1
1
1
1
1
1
1
1
1
1
2,3
2,3
2,3
2,3
2,3
2,3
2,3
2,3
2,3
2,3
V
I
OUT
= 100% rated load
Note 4
1.47
1.77
2.47
3.27
4.95
11.88
14.85
±4.95
±11.88
±14.85
1.43
1.73
2.43
3.23
4.90
11.75
14.70
±4.90
±11.78
±14.70
1
1
1
1
1
1.50
1.53
1.80
1.83
2.50
2.53
3.30
3.33
5.00
5.05
12.00
12.12
15.00
15.15
±5.00
±5.05
±12.00 ±12.12
±15.00 ±15.15
1.57
1.87
2.57
3.37
5.10
12.24
15.30
±5.10
±12.24
±15.30
12
14.4
20
20
20
V
V
I
OUT
= 100% rated load
Notes 4, 13
1,2,3
V
IN
= 18, 28, 40 Volts, Note 2
W
For Notes to Electrical Performance Characteristics, refer to page 6.
3
International Rectifier HiRel Products, Inc.
2020-07-28
(28V Input, Single/Dual Output)
Electrical Performance Characteristics
(continued)
Parameter
Output current (I
OUT
)
LSO2801R5S
LSO2801R8S
LSO2802R5S
LSO2803R3S
LSO2805S
LSO2812S
LSO2815S
LSO2805D
LSO2812D
LSO2815D
Line regulation (VR
LINE
)
All Single and Dual Output Models
Load regulation (VR
LOAD
)
All Single Output Models
Total regulation (Line and Load)
Cross regulation (VR
CROSS
)
LSO2805D
LSO2812D
LSO2815D
Input Current, no load (I
IN
)
LSO2801R5S
LSO2801R8S
LSO2802R5S
LSO2803R3S
LSO2805S
LSO2812S
LSO2815S
LSO2805D
LSO2812D
LSO2815D
Input current inhibited
Output Ripple (V
RIP
)
LSO2801R5S
LSO2801R8S
LSO2802R5S
LSO2803R3S
LSO2805S
LSO2812S
LSO2815S
LSO2805D
LSO2812D
LSO2815D
Group A
Subgroup
Conditions
-55°C
T
C
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
Limits
Min
Nom
Max
Unit
LSO SERIES
1,2,3
V
IN
= 18, 28, 40 Volts, Note 2
Either Output, Note 3
Either Output, Note 3
Either Output, Note 3
0
0
0
0
0
0
0
0
0
0
-0.5
-1.0
8.0
8.0
8.0
7.57
6.0
2.5
2.0
4.8
2.3
1.6
0.5
1.0
A
1,2,3
1,2,3
V
IN
= 18, 28, 40 Volts
I
OUT
= 0, 50%, 100% rated, Note 4
V
IN
= 18, 28, 40 Volts
I
OUT
= 0, 50%, 100% rated, Note 4
V
IN
= 18 to 40 Volts
Min load to full load
Dual model is measured
from +Output to -Output, Note 13
V
IN
= 18, 28, 40 Volts
Duals only, Note 5
%
%
1,2,3
-1.0
1.0
%
1,2,3
-5.0
-3.0
-3.0
0
0
0
0
0
0
0
0
0
0
5.0
3.0
3.0
60
60
60
60
70
70
70
70
100
100
8.0
35
35
35
35
50
50
50
50
50
50
%
1,2,3
I
OUT
= 0, Pin 3 open
mA
1,2,3
Pin 4 shorted to Pin 3
mA
1,2,3
V
IN
= 18, 28, 40 Volts
I
OUT
= 100% rated load
Notes 4, 6
mVp-p
For Notes to Electrical Performance Characteristics, refer to page 6.
4
International Rectifier HiRel Products, Inc.
2020-07-28
(28V Input, Single/Dual Output)
Electrical Performance Characteristics
(continued)
Parameter
Switching frequency (F
S
)
Efficiency (E
FF
)
LSO2801R5S
LSO2801R8S
LSO2802R5S
LSO2803R3S
LSO2805S
LSO2812S
LSO2815S
LSO2805D
LSO2812D
LSO2815D
Input under voltage lockout
(UVLO)
(turn off when input voltage
decreasing)
Input under voltage release (UVR)
(turn on when input voltage rising)
Input under voltage
Hysteresis (UVR-UVLO)
Input current telemetry ratio (ICT)
Group A
Subgroup
1,2,3
Conditions
-55°C
T
C
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
Limits
Min
425
60
63
67
71
77
77
77
76
78
78
Nom
500
62
65
69
73
80
80
80
79
81
81
Max
575
Unit
kHz
LSO SERIES
1,2,3
I
OUT
= 100% rated load
Note 4
%
1,2,3
1,2,3
1,2,3
1,2,3
No load to full load, Notes 4
No load to full load, Notes 4
No load to full load, Notes 4
I
OUT
= 100% rated load, Note 4
14.0
16.5
V
15.5
1.0
1.4
17.9
3.0
1.6
V
V
V/A
% of
nominal
Vout
V
A
V
%
W
mVpk
s
mVpk
Overvoltage protection (OVP)
Output voltage threshold
(for single and each of dual output
models)
Enable Input (Inhibit Function)
open circuit voltage
drive current (sink)
voltage range
Current Limit Point
Expressed as a percentage
of full rated load current
Power dissipation, load fault (P
D
)
Output response to
step load changes (V
TLD
)
Recovery time,
step load changes (T
TLD
)
Output response to
step line changes (V
TLN
)
Recovery Time,
step line changes (T
TLN
)
1,2,3
No load to full load, Notes 1, 4
115
3.0
125
6.0
100
50
145
16
Note 1
-0.5
105
1,2,3
1,2,3
4,5,6
4,5,6
V
OUT
= 90% of Nominal, Note 4
Short Circuit, Overload, Note 8
Half Load to/from Full Load, Notes 4,9
-300
300
200
Half Load to/from Full Load, Notes
4,9,10
18V to/from 40V
I
OUT
= 100% rated load, Notes 1,4,11
18V to/from 40V
I
OUT
= 100% rated load, Notes
1, 4,10,11
-300
300
200
s
For Notes to Electrical Performance Characteristics, refer to page 6
5
International Rectifier HiRel Products, Inc.
2020-07-28
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