PD-96964B
HYBRID - HIGH RELIABILITY
RADIATION HARDENED
DC/DC CONVERTER
Description
The LS-Series of DC/DC converters are, high reliability
devices designed for hostile radiation hardened
environments. The LS-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-975. Extensive
documentation including, thermal analysis, stress
analysis and reliability predictions are available.
The LS-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. They are
enclosed in a hermetic 1.5" x 2.3" x 0.425" steel package
and weigh less than 80 grams. The package utilizes
rugged ceramic feed-through copper core pins and is
sealed using parallel seam welding.
The LS-Series of DC/DC converters provide same
mechanical outline, power ratings, for backward pin
compatibility, to their lower radiation tolerant counterpart
M3L and Military series ATS DC/DC converters. The
common platform design allows for similarity between
military and space system architectures. For higher
output power applications the HM, M3H and M3G-Series
of DC/DC converters are recommended.
Manufactured in a facility fully qualified to MIL-PRF-
38534, these converters are fabricated utilizing DSCC
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.
LS-SERIES
28V Input, Single/Dual Output
LS
Features
n
18 to 40V DC Input Range
n
Total Ionization Dose > 100K Rad(Si)
n
SEE Hardened to LET (Heavy Ions) up to
2
82 MeV
•
cm /mg (SEU, SEL, SEGB, SEGR)
n
Internal EMI filter; Converter Capable of
meeting MIL-STD-461C CE03
n
Low Weight, < 80 grams
n
Magnetically Coupled Feedback
n
Up to 30W Output Power
n
Single and Dual Output Models Include
1.5, 2.5, 3.3, 5, 12, 15,
±5, ±12
and
±15V
n
High Efficiency - to 83%
n
100MΩ @ 500VDC Isolation
n
Under-Voltage Protection
n
Short Circuit and Overload Protection
n
Adjustable Output Voltage
n
External Inhibit
n
> 4,000,000 Hour MTBF (SF)
n
Standard Microcircuit Drawings Available
Applications
n
n
n
n
n
Geo Synchronous Satellite
Low Earth Orbit
Deep Space Probe
Communication and Display Systems
Payload and Experiment LVPS
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01/08/08
LS-SERIES
Circuit Description
The LS-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 and protection against output over
voltage in the event of an internal control loop failure.
An internal EMI filter allows the converter to meet
the conducted emissions requirements of MIL-STD-
461C on the input power leads.
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.
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 11V with respect to
the input return (pin 2).
The output voltage of all models can be adjusted
using a single external resistor.
Design Methodology
The LS-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-975. 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
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LS-SERIES
Absolute Maximum Ratings
Input voltage range
Output power
Lead temperature
Operating case temperature
Storage temperature
-0.5Vdc to +60Vdc
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
Output power
Operating case temperature
Operating case temperature
2
1
+18Vdc to +40Vdc
0 to Max. Rated
-55°C to +85°C
-55°C to +70°C
Electrical Performance Characteristics
Parameter
Group A
Subgroup
1. Input voltage rating is BOL. Input voltage range reduced to
20 to 40VDC for EOL.
2. Meets de-rating per MIL-STD-975
Limits
Min
18
Nom
28
1.50
2.50
3.30
5.00
12.00
15.00
±5.00
±12.00
±15.00
Max
40
1.53
2.53
3.33
5.05
12.12
15.15
±5.05
±12.12
±15.15
1.57
2.57
3.37
5.10
12.24
15.30
±5.10
±12.24
±15.30
12
20
25
30
8.0
8.0
7.57
6.0
2.5
2.0
4.8
2.3
1.6
0.5
Unit
V
Conditions
-55°C
≤
T
C
≤
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
Input Voltage
Output Voltage ( Vout )
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
Output power ( P
OUT
)
LS2801R5S
LS2802R5S
LS2803R3S
All Others
Output current ( I
OUT
)
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
Line regulation ( VR
LINE
)
Load regulation ( VR
LOAD
)
LS2801R5S
LS2802R5S
All others
Cross regulation ( VR
CROSS
)
LS2805D
LS2812D
LS2815D
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
I
OUT
= 100% rated load
Note 4
1.47
2.47
3.27
4.95
11.88
14.85
±4.95
±11.88
±14.85
1.43
2.43
3.23
4.90
11.76
14.70
±4.90
±11.76
±14.70
0
0
0
0
0
0
0
0
0
0
0
0
0
-0.5
V
I
OUT
= 100% rated load
Notes 4, 14
V
1,2,3
V
IN
= 18, 28, 40 Volts, Note 2
W
1,2,3
V
IN
= 18, 28, 40 Volts, Note 2
A
Either Output, Note 3
Either Output, Note 3
Either Output, Note 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
%
1,2,3
-2.0
-1.2
-1.0
-5.0
-3.0
-3.0
2.0
1.2
1.0
5.0
3.0
3.0
%
1,2,3
V
IN
= 18, 28, 40 Volts
Duals only, Note 5
%
For Notes to Electrical Performance Characteristics, refer to page 5
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3
LS-SERIES
Electrical Performance Characteristics
Parameter
Input Current, no load ( I
IN
)
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
Input current inhibited
Output Ripple, ( V
RIP
)
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
Switching frequency ( F
S
)
Efficiency ( E
FF
)
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
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
Group A
Subgroup
( continued )
Limits
Min
Nom
Max
60
60
60
70
70
70
70
100
100
8.0
35
35
35
50
70
80
80
80
80
425
500
64
72
76
82
82
82
83
83
83
12
5.0
50
145
575
Unit
Conditions
-55°C
≤
T
C
≤
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
I
OUT
= 0, Pin 4 open
1,2,3
mA
1,2,3
1,2,3
Pin 4 shorted to pin 2
V
IN
= 18, 28, 40 Volts
I
OUT
= 100% rated load
Notes 4, 6
mA
mV p-p
1,2,3
1,2,3
I
OUT
= 100% rated load
Note 4
KHz
61
68
72
78
78
78
79
79
79
9.5
-0.5
%
Note 1
V
mA
V
%
V
out
= 90% of Nominal, Note 4
105
1,2,3
4,5,6
4,5,6
Short Circuit, Overload, Note 8
Half Load to/from Full Load, Notes 4,9
Half Load to/from Full Load, Note
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
14
300
200
300
200
W
mV pk
µs
mV pk
µs
For Notes to Electrical Performance Characteristics, refer to page 5
4
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LS-SERIES
Electrical Performance Characteristics
Parameter
Turn-on Overshoot (V
OS
)
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
Turn-on Delay (T
DLY
)
Capacitive Load (CL)
LS2801R5S
LS2802R5S
LS2803R3S
LS2805S
LS2812S
LS2815S
LS2805D
LS2812D
LS2815D
Line Rejection
Isolation
Device Weight
MTBF
MIL-HDBK-217F2, SF, 35°C
4.0 x 10
6
( continued )
Limits
Min
Nom
Max
150
250
330
500
1000
1000
500
1000
1000
10
2500
2500
2200
1000
180
120
500
90
60
35
100
80
50
Unit
Group A
Subgroup
Conditions
-55°C
≤
T
C
≤
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
10% Load, Full Load
Notes 4,12
4,5,6
mV
0
I
OUT
= 100% rated load
No effect on DC performance
Notes 1, 4, 7
ms
µF
Each output on duals
I
OUT
= 100% rated load
DC to 50KHz, Notes 1, 4
Input to Output or Any Pin to Case
except pin 3, test @ 500VDC
1
1
dB
MΩ
g
Hr
Notes for Electrical Performance Characteristics
Table
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Parameter is tested as part of design characterization or after design changes. Thereafter, parameter
shall be guaranteed to the limits specified.
Parameter verified during line and load regulation tests.
Output load current must be distributed such that at least 20% of the total load current is being provided by
one of the outputs.
Load current split equally between outputs on dual output models.
Cross regulation is measured with 20% rated load on output under test while changing the load on the
other output from 20% to 80% of rated.
Guaranteed for a D.C. to 20MHz bandwidth. Tested using a 20KHz to 10MHz bandwidth using the circuit
on page 6.
Capacitive load may be any value from 0 to the maximum limit without compromising dc performance. For
a capacitive load in excess of the maximum limit, consult the factory.
Overload power dissipation is defined as the device power dissipation with the load set such that V
OUT
=
90% of nominal.
Load step transition time
≤
10µs.
Recovery time is measured from the initiation of the transient to where V
OUT
has returned to within ±1% of
its steady state value.
Line step transition time
≤
100µs.
Turn-on delay time from either a step application of input power or a logic low to a logic high transition on
the inhibit pin (pin 4) to the point where V
OUT
= 90% of nominal.
For operation at temperatures between +85°C and 125°C, de-rate the maximum output power linearly from
100% to 75%.
End of life (EOL) is
±3%
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