PD-94535K
M3G-SERIES
HYBRID-HIGH RELIABILITY
RADIATION HARDENED
DC-DC CONVERTER
Description
The M3G-Series of DC-DC converters are radiation
hardened, high reliability converters designed for
extended operation in hostile environments. Their small
size and low weight make them ideal for applications
such as geostationary earth orbit satellites and deep
space probes. They exhibit a high tolerance to total
ionizing dose, single event effects and environmental
stresses such as temperature extremes, mechanical
shock, and vibration. All components are fully derated
to meet the requirements of MIL-STD-975, MIL-STD-
1547 and GSFC PPL-21 Appendix B.
The converters incorporate a fixed frequency single
ended forward topology with magnetic feedback and
an internal EMI filter that utilizes multilayer ceramic
capacitors that are subjected to extensive lot screening
for optimum reliability. These converters are capable
of meeting the conducted emissions and conducted
susceptibility requirements of MIL-STD-461C without
any additional components. External inhibit and
synchronization input and output allow these converters
to be easily incorporated into larger power systems.
They are enclosed in a hermetic 3" x 2" x 0.475" package
constructed of an Aluminum-Silicon-Carbide (AlSiC)
base and an Alloy 48 ring frame and they weigh less
than 110 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 DSCC
qualified processes. For available screening options,
refer to device screening table in the data sheet.
Non-flight versions of the M3G-Series converters are
available for system development purposes. Variations
in electrical specifications and screening to meet custom
requirements can be accommodated.
28V Input, Triple Output
M3G
Features
n
SEE Hardened up to 82 MeV
.
cm
2
/mg
n
Internal EMI filter; Converter Capable of
meeting MIL-STD-461C CE03
n
Low Weight, < 110 grams
n
Magnetically Coupled Feedback
n
18V to 50V DC Input Range
n
Up to 40W Output Power
n
Triple Output Models Include
+5V and
±
12V or
±
15V
n
Main Output Isolated from Dual Outputs
n
High Efficiency - to 80%
n
-55°C to +125°C Operating Temperature Range
n
100M
Ω
@ 500VDC Isolation
n
Under-Voltage Lockout
n
Synchronization Input and Output
n
Short Circuit and Overload Protection
n
Output Over Voltage Limiter
n
External Inhibit
n
> 5,000,000 Hour MTBF
n
Standard Microcircuit Drawings Available
n
Total Dose > 200 krad(Si),
typically usable to > 300 krad(Si)
Applications
n
n
n
Geostationary Earth Orbit Satellites (GEO)
Deep Space Satellites / Probes
Strategic Weapons and Communication
Systems
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05/07/10
M3G-SERIES
Circuit Description
The M3G-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.
An internal EMI filter allows the converter to meet the
conducted emissions requirements of MIL-STD-461C
on the input power leads. A two-stage output filter
reduces the typical output ripple to less than 20mV
peak-to-peak.
The main ( +5 volt ) output is regulated by the control
loop and typically exhibits better than 1% regulation.
The auxiliary ( ±12 volt or ±15 volt ) outputs are
maintained through tight coupling in the power
transformer and main output filter inductor and
typically exhibit better than 5% regulation. The main
output and auxiliary outputs are isolated from each
other.
Output power is limited under any load fault condition
to approximately 125% of rated. An overload
condition causes the converter output to behave like
a constant current source with the output voltage
dropping 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 under-voltage lockout circuit prohibits the
converter from operating when the line voltage is too
low to maintain the output voltage. The converter will
not start until the line voltage rises to approximately
16.5 volts and will shut down when the input voltage
drops below 15.5 volts. The one volt of hysteresis
reduces the possibility of line noise interfering with
the converter’s start-up and shut down.
An external inhibit port is provided to control converter
operation. The nominal threshold relative to the input
return (pin 2) is 1.4V. If 2.0 volts or greater are applied
to the Inhibit pin (pin 3) then the converter will
operate normally. A voltage of 0.8V or less will cause
the converter to shut-down. The pin may be left
open for normal operation and has a nominal open
circuit voltage of 4.0V.
Synchronization input and output allow multiple
converters to operate at a common switching
frequency. Converters can be synchronized to one
another or to an externally provided clock. This can
be used to eliminate beat frequency noise or to avoid
creating noise at certain frequencies for sensitive
systems.
Design Methodology
The M3G-Series was developed using a proven
conservative design methodology which includes
selecting radiation tolerant and established reliability
components and fully derating to the requirements
of MIL-STD-975 and MIL-STD-1547. Careful sizing
of decoupling capacitors and current limiting
resistors minimizes the possibility of photo-current
burn-out. Heavy derating of the radiation hardened
power MOSFET virtually eliminates the possibility
of SEGR and SEB. A magnetic feedback circuit is
utilized instead of opto-couplers to minimize
temperature, radiation and aging sensitivity. PSPICE
and RadSPICE were used extensively to predict
and optimize circuit performance for both beginning
and end-of-life. Thorough design analyses include
Radiation Susceptibility (TREE ), Worst Case, Stress,
Thermal, Failure Modes and Effects (FMEA) and
Reliability (MTBF).
2
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M3G-SERIES
Specifications
Absolute Maximum Ratings
Input voltage range
Output power
Lead temperature
Operating temperature
Storage temperature
-0.5Vdc to +80Vdc
Internally limited
+300°C for 10 seconds
-55°C to +135°C
-55°C to +135°C
Recommended Operating Conditions
Input voltage range
Input voltage range
1
Output power
Operating temperature
Operating temperature
1
+18Vdc to +60Vdc
+18Vdc to +50Vdc
0 to Max. Rated
2
1
-55°C to +125°C
-55°C to +70°C
2
Meets derating per MIL-STD-975
For operation at +125°C see table note 14
Electrical Performance Characteristics
Group A
Subgroup
1,2,3
1
Conditions
-55°C
≤
T
C
≤
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
Note 2
I
OUT
= 100% rated load, Note 5
Limits
Min
18
4.98
±11.50
±14.60
4.93
±11.30
±14.40
V
IN
= 18, 28, 50 Volts, Note 2
V
IN
= 18, 28, 50 Volts, Notes 2,3,4,5
0
400
83
67
-10
-120
-150
-50
-400
-500
Nom
28
5.00
±11.80
±14.90
Max
50
5.02
±12.10
±15.20
5.07
±12.30
±15.40
40
4000
±833
±667
10
120
150
50
400
500
W
Unit
V
Parameter
Input Voltage
Output Voltage ( Vout )
(main)
M3G280512T (aux.)
M3G280515T (aux.)
(main)
M3G280512T (aux.)
M3G280515T (aux.)
Output power ( P
OUT
)
Output current ( I
OUT
)
(main)
M3G280512T (aux.)
M3G280515T (aux.)
Line regulation ( VR
LINE
)
(main)
M3G280512T (aux.)
M3G280515T (aux.)
Load regulation ( VR
LOAD
)
(main)
M3G280512T (aux.)
M3G280515T (aux.)
Cross regulation ( VR
CROSS
)
(main)
M3G280512T ( aux.)
M3G280515T (aux.)
Input current ( I
IN
)
V
2,3
1,2,3
1,2,3
mA
1,2,3
V
IN
= 18, 28, 50 Volts
I
OUT
= 10, 50%, 100% rated
Note 5
I
OUT
= 10%, 50%, 100% rated
V
IN
= 18, 28, 50 Volts
Notes 5,13
V
IN
= 18, 28, 50 Volts
I
OUT
= 2.5A to 1A and 2.5 to 4A on main
and ±half rated on aux. outputs
I
OUT
= 0, Pin 3 open
Pin 3 shorted to pin 2
mV
1,2,3
mV
1,2,3
1,2,3
-3.5
-3.0
3.5
3.0
80
5.0
%
mA
For Notes to Specifications, refer to page 5
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M3G-SERIES
Electrical Performance Characteristics
Group A
Subgroup
1,2,3
( continued )
Limits
Min
Nom
25
30
30
450
75
500
79
Max
50
60
75
550
Unit
Parameter
Output ripple ( V
RIP
)
(main)
M3G280512T (aux.)
M3G280515T (aux.)
Switching frequency ( F
S
)
Efficiency ( E
FF
)
Inhibit Input
open circuit voltage
drive current ( sink )
voltage range
Synchronization Input
frequency range
pulse high level
pulse low level
pulse transition time
pulse duty cycle
Current Limit Point
Expressed as a percentage
of full rated output power
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
)
Turn-on Response
Overshoot (V
OS
)
(main)
(aux.)
Turn-on Delay (T
DLY
)
Capacitive Load (CL)
(main)
(Each aux. output)
Conditions
-55
°
C
≤
T
C
≤
+85
°
C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
V
IN
= 18, 28, 50 Volts
I
OUT
= 100% rated load, Notes 5, 6
Sync. Input (Pin 4) open
I
OUT
= 100% rated load
Note 5
Note 1
mV p-p
KHz
%
1,2,3
1,2,3
3.0
-0.5
5.0
100
50
600
10.0
0.5
80
135
150
20
V
µA
V
KHz
V
V
V/µs
%
%
W
mV pk
µs
mV pk
µ
s
Ext. Clock on Sync. Input (Pin 4)
Note 1
450
4.0
-0.5
40
20
1,2
3
1,2,3
4,5,6
4,5,6
V
out
= 90% of Nominal, Note 5
Short Circuit, Overload, Note 8
Half Load to/from Full Load, Notes 5,9
Half Load to/from Full Load, Note 5,9,10
18V to/from 50V
I
OUT
= 100% rated load, Notes 1,5,11
18V to/from 50V
I
OUT
= 100% rated load, Notes 1,5,10,11
-300
-300
300
200
300
200
4,5,6
No Load, Full Load, Notes 5,12
10% of Nominal
1.0
500
10
5.0
mV
%
ms
I
OUT
= 100% rated load, No effect on DC
performance, Notes 1, 5, 7
1000
200
µF
For Notes to Specifications, refer to page 5
4
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M3G-SERIES
Electrical Performance Characteristics
Group A
Subgroup
( continued )
Limits
Min
40
100
110
Nom
60
Max
Unit
dB
MΩ
g
Hrs
Parameter
Line Rejection
Isolation
Device Weight
MTBF
Conditions
-55°C
≤
T
C
≤
+85°C
V
IN
= 28V DC ± 5%, C
L
= 0
unless otherwise specified
I
OUT
= 100% rated load
DC to 50KHz, Notes 1,5
Input to Output or any pin to case
Except pin 10, test @500VDC
MIL-HDBK-217F2, SF, 35°C
1
5 x 10
6
Notes: Electrical Performance Characteristics
1.
2.
3.
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.
Although operation with no load is permissible, light loading on the main (+5 volt) output may cause the output
voltage of the auxiliary outputs
(±12 volt or ±15 volt) to drop out of regulation. It is therefore recommended that at least 200 mA or 20 percent
of the total output power, whichever is greater, be taken from the main (+5 volt) output.
Although operation with no load is permissible, heavy loading on the main (+5 volt) output may cause the
output voltage of the auxiliary outputs
(±12 volt or ±15 volt) to rise out of regulation. It is therefore recommended that at least 50 mA or 20 percent
of the total output power, whichever is greater, be taken from the auxiliary (±12 volt or ±15 volt) outputs.
Unless otherwise specified, “Rated” load is 20W on the main (+5 volt) output and 10 watts each on the auxiliary
(±12 volt or ±15 volt) outputs. Load currents of up to 5A and ±1A on the main and auxiliary outputs respec-
tively are acceptable as long as the total output power does not to exceed 40 watts.
Guaranteed for a D.C. to 20MHz bandwidth. Tested using a 20KHz to 10MHz bandwidth.
Capacitive load may be any value from 0 to the maximum limit without compromising dc performance.
A capacitive load in excess of the maximum limit may interfere with the proper operation of the converter’s
overload protection, causing erratic behavior during turn-on.
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
³
10
µs.
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
³
100
µs.
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 3) to the point where V
OUT
= 90% of nominal.
Load is varied for output under test while the remaining outputs are loaded at 50% of rated. Regulation relative
to output voltage at 50% rated load.
Although operation at temperatures between +85°C and +125°C is guaranteed, no parametric limits are
specified.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
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