Page 1

Power Management Group

RADIATION HARDENED ISOLATED DC/DC CONVERTERS SA50-28-5/15T 50 Watts Total Power +5Vdc±15Vdc Triple Output

Microsemi Power Management Group (PMG) multiple decades of fault free heritage complex custom (radiation hardened) switching power design and systems are now complimented with the introduction of “SA Series” Standard Radiation Hardened DC/DC converter modules

Standard Product Offering 

+28 Vdc Satellite Input Interface

100kRad (Si) TID; Single Event Effect rated

Surface Mount Construction (non-hybrid)

50W total power, high efficiencies 83%+

Patented Magnetic Feedback

Isolated Synchronization Input

Primary referenced ON – OFF command

Over-current Protection

Input Under-voltage lockout

MIL-STD-1547B design de-rating criteria

100% Space level Environmental Screening

Standard Mounting 2.05” x 3.05” x 0.475”

Single, Dual & Triple Output Options

SEE > 80 MeV•cm2 /mg

SA50-28-5/15T Rev A

Application Scenarios Power Systems & Devices

Typical Threat Environments

Military Surveillance & Navigation Communications Satellites (GEO) (MEO) (LEO) Deep Space Probes EPS, Payload & Subsystems

• Primary - Total Dose - SEE - Dose-Rate-Upset • Secondary - Displacement Damage

Commercial Communications Monitoring Satellites Launch Vehicles

• Primary - SEE - Total Dose (NWE) • Secondary - Total Dose (natural) - Displacement Damage

Tactical Military Systems Including Avionics

• Primary - Dose-rate (upset & Latch up) - SEE (for avionics) • Secondary - Total dose - Neutron irradiation

ICBM & Strategic Interceptor

• Primary - Neutron Irradiation - Dose-Rate - upset/Survivability • Secondary - Total Ionizing Dose

Microsemi Corp.

Page 1 of 14

Radiation Performance Rating

Magnetics are designed, manufactured and screened in accordance






All bipolar microcircuits contained within the SA50 series

Qualification test per MIL-STD-981 can be performed if

design are characterized for enhanced low dose rate

required by the customer at additional charge. Part De-

sensitivity (ELDRS), with data constructed at a dose rate

rating is in accordance with MIL-STD-1547B and MIL-

of 0.01 rad (Si)/s or less with assessments in both a

STD-975M. The enclosure is of machined Aluminum

biased and unbiased state

construction. The finish is conductive Alodyne per MILC-5541, Type 3.

Test Total Ionizing Dose






kRads (Si)


Note: The product may be upgraded to meet TOR2006(8583)-5236

Single Event Effects SEU, SEL, SEGR, SEB







82 MeV•cm2 /mg


Workmanship is in accordance with the highest industry standards, including ANSI/STD-001 Class 3.

Qualification and Acceptance Testing Qualification and inspection/testing minimally include;

Alternate Version (-P)

Random Vibration, Mechanical Shock, Thermal Vacuum, Thermal Cycling, EMI, and Burn-in testing with periodic

The SA50 series alternate version is offered for

corresponding performance measurements as required.


All converter modules are pre-screened according to

Selective component alternatives are employed within

specific in-line acceptance testing. These processes

the design, specifically by utilizing “B” level or lower

include multiple cycles of High and Low temperature

component substitutions. The part substitutions do not

cycling, Random vibration, with Pre and Post Electrical

impact electrical performance characteristics.






Performance Verification prior to delivery.

Parts, Materials and Processes Internal






screened in accordance with GSFC EEE-INST-002 (Instruction for EEE Parts Selection, Screening, and Qualification).

SA50-28-5/15T Rev A

Microsemi Corp.

Page 2 of 14

Ratings Absolute Maximum Ratings VIN range Output power Lead temperature Operating temperature Storage temperature Shock Constant Acceleration

-0.5Vdc to +60Vdc 50 Watts +300°C for 10 Sec. -55°C to +125°C -55°C to +125°C 1500 gpk, 0.5 msec ½ sine 50 g

Random Vibration

24.06 grms , 50-2000 Hz

Recommended Operating Conditions VIN range

+17Vdc to +50Vdc

Output power

2 watts to Max. Rated

Operating temperature c

-55°C to +125°C

Operating temperature a,b

-55°C to +70°C

a Meets derating per MIL-STD-975M b Meets derating per MIL-STD-1547B c For operation at +125°C see table Note 15

Electrical Specifications Group A Subgroup 1 25°C 2 -55°C 3 85°C

Conditions -55°C ≤ TCASE ≤ +85°C VIN = 28V DC ± 5%, CL = 0 unless otherwise specified

Input Voltage Output Voltage ( VOUT ) (main) (aux.) (main) (aux.)


Note 2


IOUT = 100% rated load, Note 5


IOUT = 100% rated load, Note 5

Output Power (POUT)


VIN = 17, 28, 50 Volts, Notes 2,4





VIN = 17, 28, 50 Volts, Notes 2,3,4,5

400 100

4000 1000



VIN = 17, 28, 50 Volts IOUT =10%, 50%, 100% rated, Notes 5, 14

-10 -150

10 150



VIN = 17, 28, 50 Volts IOUT =10%, 50%, 100% rated, Note 5, 13

-50 -500

50 500






Output current (IOUT) (main) (aux.) Line regulation ( VRLINE ) (main) (aux.) Load regulation ( VRLOAD) (main) (aux.)



Min 17

Nom 28

Max 50

5.08 14.46 5.05 14.25

5.10 14.75 5.10 14.75

5.12 15.05 5.15 15.25


Cross regulation (VRCROSS) (aux.)

SA50-28-5/15T Rev A


VIN = 17, 28, 50 Volts IOUT = 2.5A to 1A and 2.5A to 4A on main and ±half rated on aux. outputs

Microsemi Corp.

Page 3 of 14

Group A Subgroup 1 25°C 2 -55°C 3 85°C

Conditions -55°C ≤ TCASE ≤ +85°C VIN = 28V DC ± 5%, CL = 0 unless otherwise specified


IOUT = 0, Pin 3 open Pin 3 shorted to pin 2

Nom 100 2.0

Max 150 5.0


VIN = 17, 28, 50 Volts IOUT = 100% rated load, Notes 5, 6

25 37.5

50 75

mV p-p

Switching frequency (FS)


Sync. Input (Pin 4) open





Efficiency ( EFF )


IOUT = 100% rated load, Note 5



Note 1

4.5 1000

Input current (IIN) Output ripple (VRIP) (main) (aux.)

Inhibit Input ON voltage (or Open Collector) OFF drive current (sink) OFF voltage


Ext. Clock on Sync. Input (Pin 4) Note 1

Current Limit Point Expressed as a % of full rated output current


VOUT = 90% of Nominal, Note 5

Power dissipation, load fault (PD)


Short Circuit, Overload, Note 8

Output response to step load changes (VTLD)


Recovery time, step load changes (TTLD)


Half Load to/from Full Load, Notes 5,9

17V to/from 50V IOUT = 100% rated load, Notes 1, 5,11

Recovery time, step line changes (TTLN)

17V to/from 50V IOUT = 100% rated load, Notes 1, 5,11


Capacitive Load (CL) (main) (Each aux. output)

No Load, Full Load Notes 5,12









mV pk




mV pk



500 750 5.0

mV mV mSec

1000 200

μF μF






DC to 50KHz, Notes 1, 5 IOUT = 100% rated load


Input (Pins 1,2,3) to Outputs Any Pin to Case (except pin 6) Sync and Sync Rtn to any pin and case



SA50-28-5/15T Rev A


MΩ 110

MIL-HDBK-217F2, SF, 35°C

Microsemi Corp.

V μA V

kHz V V V/μs %

Device Weight MTBF


300 10.0 0.5

IOUT = 100% rated load, No effect on DC performance, Notes 1, 5, 7

Line Rejection


250 4.0 -0.5 200 10

Half Load to/from Full Load, Note 5,9,10

Output response to step line changes (VTLN)




Synchronization Input frequency range pulse high level pulse low level pulse transition rate pulse duty cycle

Turn-on Response Overshoot (VOS) (main) Overshoot (VOS) (aux.) Turn-on Delay (TDLY)



g Hrs

Page 4 of 14

Test Total Ionizing Dose (Gamma) Dose Rate (Gamma Dot) Temporary Saturation Survival

Radiation Tests Conditions MIL-STD-883, Method 1019 Operating bias applied during exposure, MIL-STD-883, Method 1023 Operating bias applied during exposure, Full Rated Load, VIN = 28V

1E8 4E10


MIL-STD-883, Method 1017



Heavy ions (LET) Operating bias applied during exposure,



Neutron Fluence Single Event Effects SEU, SEL, SEGR, SEB






KRads (Si) Rads (Si) /sec Neutrons /cm2 MeV•cm2 /mg

Notes: Electrical Performance Characteristics 1. Parameter guaranteed by design. 2. Parameter verified during line and load regulation tests. Regulation is specified for 10% to 100% loading on all outputs. 3. Auxiliary output regulation is not maintained if main output load is less than 10%. 4. Auxiliary outputs require at least 10% loading for specified regulation. Voltage may increase at lighter loads and is ultimately limited by overvoltage zener diodes. 5.Unless otherwise specified, “Rated” load is 20W on the main (+5 volt) output and 15 watts each on the auxiliary (±15 volt) outputs. Load currents of up to 5A and 6. Guaranteed for a D.C. to 20MHz bandwidth. Tested using a 20kHz to 10MHz bandwidth. 7. 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 8. Overload power dissipation is defined as the device power dissipation with the load set such that VOUT = 90% of nominal. 9. Load step transition time ≥ 10 μs. 10. Recovery time is measured from the initiation of the transient to where VOUT has returned to within ±1% of its steady state value. 11. Line step transition time ≥ 100 μs. 12. 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 VOUT = 90% of 13. Load Regulation relative to output voltage at 50% rated load. 14. Line Regulation relative to output voltage at 28Vdc input. 15. For operation at temperatures between +85°C and +125°C, derate power linearly from 50 watts to zero. Parameter limits are not guaranteed.

Pin Designation Pin # 1 2 3 4 5 6


Pin # 7 8 9 10 11 12

Designation 15V B RTN +15V B 15V A RTN +15V A +5V 5V RTN

Place a low ESR ceramic capacitor and a Tantalum capacitor within one inch of the SA50 module’s input terminals. The suggested minimum values are 4.7uF and 25uF respectively. SA50-28-5/15T Rev A

Microsemi Corp.

Page 5 of 14

The Power Supply can sustain short circuit operation indefinitely. When short circuited, the Power Supply output cycles at approximately 2% duty cycle. Short circuit operation begins when the Power Supply output voltage falls below approximately 60% of its nominal value.

Output ripple is measured as shown:

SA50-28-5/15T Rev A

Microsemi Corp.

Page 6 of 14

Theory of Operation for the SA50 28 Series Input voltage is applied to the input EMI filter. This filter consists of differential and common mode components that attenuate the internal converter switching noise. Additional external filtering is required to ensure compliance to MIL-STD461 levels.

Internal controller bias is supplied during power up and in over-current scenarios via Darlington startup transistors off the input line. The controller power supply ramps up to the turn on point where it starts to supply drive to the main power converter MOSFET Q1. Under normal load conditions the output voltage will come up and a “Bootstrap� voltage is fed back to stabilize the Bias supply eliminating power loss in the start-up transistors.

SA50-28-5/15T Rev A

Microsemi Corp.

Page 7 of 14

Main power conversion occurs in the forward converter Q1 and associated Transformer. The secondary windings develop the required output voltages in parallel. A coupled inductor promotes good output cross regulation. Elimination of secondary side post regulators promotes high efficiency performance.

Output voltages are regulated on the main output secondary side. A TL1431 reference develops a current mode error signal which is chopped by the main forward transformer voltage and the summed with the primary side converter current in a patented magnetic feedback approach. The combined “V + I� error signal is applied to the primary controller’s ramp control input to complete the regulation loop.

The primary ON OFF command disables internal switch-mode action when pulled low.

The SYNC input is fully transformer isolated to allow operation from primary or secondary referenced sync drives.

SA50-28-5/15T Rev A

Microsemi Corp.

Page 8 of 14

APPLICATION DATA Under voltage Operation: The Input Under-voltage protection feature prevents operation at an undesirably low input voltage. The outputs are guaranteed to turn on at the specified minimum input voltage and guaranteed to be disabled below 70% of the specified minimum input

Inhibit feature: An external inhibit port is provided to control converter operation. The inhibit circuit is referenced to the DC Input return. The interface is as shown below. The inhibit signal may be an open-collector or TTL type. Interface must sink 1 mA minimun to inhibit the output.

Inhibit Pin

Power Supply Output

Open > 4.5 volt Short < 3.0 volt



1K I n h ib it (3 )

V in _ R TN (2 )

Sync Input: The Power Supplyâ&#x20AC;&#x2122;s internal clock may be synchronized to an external signal. For enhanced system configuration flexibility and noise immunity, the sync input circuit is magnetically isolated from all other circuits and chassis. The interface is shown below. The circuit operates from the rising (leading) edge of the sync waveform, that generates a short synchronization pulse to the PWM controller. Note that the sync circuit DC input resistance is 500 Ohms. Specifically, the circuit driving the sync input needs to deliver a minimum of 5 mA of current into the input for a minimum of 50 ns, resulting in a minimum reflected voltage of 4 volts. Higher voltage drives are acceptable up to 10 volts, delivering approximately proportional higher current levels. Maintenance of high level voltage drive beyond 50 ns is not essential for correct synchronization function. 12 27.4

Magnitude (p-p) min. 4.0 volt max. 10.0 volt

Duty Cycle min. 10% max. 90%

511 SY NC (4) R1 P1

Rate of Rise min. 200 V/Âľsec

Frequency min. 500kHz max. 600kHz



sy nc_pulse 27.4

SA50-28-5/15T Rev A

Microsemi Corp.

Page 9 of 14

Wire current: -:E1#P / mA

Typical Sync Operation input current 10 8 6 4 input voltage

2 -0

E1-P / V

4 3 2 1

sync_pulse / V

0 Sync pulse beta = 17

5 4 3 2 1 -0













Short Circuit/ Over current limit protection: The output current is limited by the built in current limit circuit, to protect the Power Supply and the load from overstress.

The weighted sum of main and auxiliary output currents is controlled. The maximum current of any one of the outputs can be calculated using the following relationship:

5.5×I15A + 5.5× I15B + 2 × I5 = 27 amps Where, I15A is the 15V A output current in amperes I15B is the 15V B output current in amperes I5 is the 5V output current in amperes

For example, if all outputs are fully loaded and the 5V output load impedance is further reduced to the current limit threshold, the resulting maximum 5V output load current is:

(27 amp - 5.5×1amp - 5.5×1amp) ×1/2 = 8 amps

The converter continues to regulate its output voltage under this loading condition. If the load impedances of any of the outputs are further decreased, the converter turns off and attempts to restart after a delay.

SA50-28-5/15T Rev A

Microsemi Corp.

Page 10 of 14

Dual Output Configuration The SA50-120 Triple configurations are readily configurable as Dual Output supplies. For balanced output Dual Supply configuration, connect Pins 8 & 9 together to form the Dual Output Common potential. Pin 7 is now the negative (â&#x20AC;&#x201C;) Dual output and Pin 10 is the positive (+) Dual output. In this configuration it is important to preload the unused 5V output with 12 ohms, representing a 10% of rated load on that output. This assures proper regulation and cross regulation of the dual outputs over their full load ranges. For an unbalanced Dual Supply configuration, connect the auxiliary outputs in parallel (Pin 10 to Pin 8 and Pin 9 to Pin 7). Since the Auxiliary and Main outputs are internally isolated, it is allowable to connect either the main output as the high side dual supply (Connect Pin 12 to Pin 10 for the Common output) or the Auxiliary output as the high side dual supply (Connect Pin 11 to Pin 9 for the common output). Again please ensure that the main output load is at least 10% of rated. Following the above guidelines, the regulation and cross regulation performance of the triple applies to the dual configurations in general.

Model Numbering Scheme

PMG-28 Series Available Data Items: Analyses & Reports: 1: Mechanical Analysis 2: Stress Analysis 3: Thermal Analysis 4: Radiation Analysis 5: Worse Case Analysis 6: FEMA 7: First Article Qualification Test Report 8: EMI Test Report

SA50-28-5/15T Rev A

Microsemi Corp.

Page 11 of 14

SA50 Mechanical Installation Application Note


Mechanical interface

The surface on which an SA50 power supply is mounted is recommended to be flat to .005 in or less, with a surface roughness of 32 microinches or less. The mounting hole pattern and housing footprint for SA50 power supplies is shown in Figure 1.

Figure 1: Mounting hole pattern and housing footprint


Mounting fasteners

The fasteners recommended for mounting of SA50 power supplies are 4-40 size fasteners, made from A-286 steel, used with NAS620C4 washers. Representative fasteners include NAS1101, NAS1352, or equivalent. The recommended torque is 6-8 in-lb.

SA50-28-5/15T Rev A

Microsemi Corp.

Page 12 of 14


Efficiency 25째C 28 volt 85.0%

Main output swept from 10% to 100% Aux load each 0.1 amp


Aux load each 0.2 amp


Aux load each 0.3 amp Aux load each 0.4 amp


Aux load each 0.5 amp

Aux load each 0.6 amp Aux load each 0.7 amp 70.0%

Aux load each 0.8 amp Aux load each 0.9 amp

Aux load each 1.0 amp 65.0%

60.0% 0 watt

10 watt

20 watt

30 watt

40 watt

50 watt

60 watt

Total output 85.0%

Efficiency 25째C 28 volt 84.0%

Main output swept from 10% to 100% load Aux load each 0.1 amp

Aux load each 0.2 amp

83.0% Efficiency

Aux load each 0.3 amp

Aux load each 0.4 amp Aux load each 0.5 amp Aux load each 0.6 amp 82.0%

Aux load each 0.7 amp Aux load each 0.8 amp

Aux load each 0.9 amp Aux load each 1.0 amp


80.0% 0.0 amp

0.5 amp

1.0 amp

1.5 amp

2.0 amp

2.5 amp

3.0 amp

3.5 amp

4.0 amp

4.5 amp

Main output load

SA50-28-5/15T Rev A

Microsemi Corp.

Page 13 of 14

Package Outline

Contact: Kent Brooten Sales Manager Power Management Group Phone: 714-994-6500, ext. 215 (USA) E-mail: Web: Address: Microsemi Corporation PMG 14930 East Alondra Blvd La Mirada, CA 90638-5752 Phone: 714-994-6500 Information furnished by Microsemi is believed to be accurate and reliable. However, no responsibility is assumed by Microsemi for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Microsemi Corporation.

SA50-28-5/15T Rev A

Microsemi Corp.

Page 14 of 14