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DESCRIPTION
The SMHF Series™of 28 V DC/DC converters offers a wide input voltage range of 16 to 40 volts and up
to 15 watts of output power.The units are capable of withstanding short term transients up to 50volts. The package is a hermetically sealed, seam-welded metal case. Flanged and non-flanged models are available.
S CREENING AND R EPORTS
SMHF converters offer three screening options (Standard,  Class H,or Class K) and three levels of radiation hardness (O, L, and R). See Tables 1, 2, and 3 for more information. Detailed reports on product performance are also available and are listed in Table 4.
C ONVERTER
D ESIGN
The SMHF converters are switching regulators that use a quasi-square wave, single-ended forward converter design with a constant switching frequency of 550 kHz. Isolation between input and output circuits is provided with a transformer in the forward path and a temperature compensated opto-coupler in the feedback control loop. The opto-coupler is radiation hardened and is especially selected for space applications.
For the SMHF dual output models, cross regulation is maintained by tightly coupled output magnetics. Up to 70% of the total output power is available from either output, providing the opposite output is simultaneously carrying 30% of the total output power. Predictable current limit is accomplished by directly monitoring the output load current and providing a constant current output above the overload point.
H IGHER P OWER D ENSITY
The SMHF Series offers a new standard of performance for small size and high power density. At just 0.33 inch high and a total foot-print of 1.7 in 2, this low profile package offers a total power density of up to 30 watts per cubic inch.
L OW N OISE ,H IGH A UDIO R EJECTION
The SMHF converters’feed-forward compensation system provides excellent dynamic response and noise rejection. Audio rejection is typically 50 dB. Typical output voltage response for a 50% to 100%
step load transient is as low as 1.3% with a 150 msec recovery time.Input ripple current is typically 35 mA p-p with output ripple voltage typically 30 mV p-p .
I NHIBIT F UNCTION
SMHF converters provide an inhibit terminal that can be used to disable internal switching, resulting in no output and very low quies-cent input current. The converter is inhibited when a TTL compatible low (≤0.8 – output disabled) 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 8.5 to 12 VDC. In the inhibit mode, a maximum of 12 mA must be sunk from the inhibit pin at 28 VDC input.
S YNCHRONIZATION
A synchronization feature is included with the SMHF Series that allows the user to match the switching frequency of the converter to the frequency of the system clock. An external synchronization feature is included that allows the user to adjust the nominally 550kHz operating frequency to any frequency within the range of 500 kHz to 600 kHz. This is initiated by applying a TTL compatible input of the desired frequency to pin 5.
S HORT C IRCUIT P ROTECTION
SMHF Series converters provide short circuit protection by restricting the output current to approximately 115% of the full load output current. The output current is sensed in the secondary stage to provide highly predictable and accurate current limiting, and to eliminate foldback characteristics.
U NDERVOLTAGE L OCKOUT
Undervoltage lockout prevents the units from operating below approximately 14 VDC input voltage to keep system current levels smooth, especially during initialization or re-start operations.
RECOMMENDED OPERATING CONDITIONS
TYPICAL CHARACTERISTICS
SYNC AND INHIBIT
ABSOLUTE MAXIMUM RATINGS
Input Voltage •16 to 40 VDC
Power Dissipation (Pd)•8
W
Output Power
•12 to 15 watts depending on model
Lead Soldering Temperature (10 sec per lead)•300°C
Storage Temperature Range (Case)•–65°C to +150°C
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DC/DC C ONVERTERS
Output Voltage Temperature Coefficient •100 ppm /°C typical •150 ppm/°C maximum Input to Output Capacitance •60 pF typicalprofile中文
Undervoltage Lockout •12 V input typical Current Limit
•115% of full load typical Isolation
•100 megohm minimum at 500 V Audio Rejection •50 dB typical
Conversion Frequency (º55°C to +125°C Tc)•Free run 550 kHz typical 480 kHz min, 620 kHz max Inhibit Pin Voltage (unit enabled)•8.5 to 12 V
Input Voltage Range
•16 to 40 VDC continuous
•0 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
SMHF SERIES SINGLE AND DUAL 15 WATT
SINGLE OUTPUT MODELS SMHF283R3S SMHF2805S SMHF2812S SMHF2815S OUTPUT VOLTA
GE Tc = 25°C    3.27  3.3  3.33  4.955  5.0511.881212.1214.851515.15VDC OUTPUT CURRENT V IN = 16 TO 40 VDC ——  2.4——  2.4——  1.25——  1.00A OUTPUT POWER V IN = 16 TO 40 VDC 0—80—120—150—15W OUTPUT RIPPLE 10 kHz - 2 MHz —60160—3080—60160—6075mV p-p VOLTAGE
Tc = –55°C TO +125°C —80240—150240—50120—100260LINE REGULATION V IN = 16 TO 40 VDC —5100—5100—5100—5100mV LOAD REGULATION NO LOAD TO FULL —2050—2050—2050—2050mV INPUT VOLTAGE CONTINUOUS 162840162840162840162840VDC NO LOAD TO FULL TRANSIENT 120 ms
0—500—500—500—50V INPUT CURRENT
NO LOAD —2565—2540—2550—2562FULL LOAD ——397—560624—680752—670752mA
INHIBITED —512—512—512—512INPUT RIPPLE 10k Hz - 10 MHz —4580—3580—3580—3580mA p-p CURRENT Tc = –55°C TO +125°C
——120——120——120——120EFFICIENCY Tc = 25°C 7073—7375—7879—7480—%LOAD FAULT 1
SHORT CIRCUIT POWER DISSIPATION —58—  3.58—  3.58—  3.57W RECOVERY 2—
7.5
30—7.530—
7.5
30—7.5
30
ms STEP LOAD 50 %–100%– 50%RESPONSE TRANSIENT –400150500–500150500–700150
700–800200800
mV pk RECOVERY 2—150300—150300—150500
—
6001200µs STEP LINE 16 TO 40 TO 16 V IN
RESPONSE  TRANSIENT 3–800550800–800550800–800550800–800550800mV pk RECOVERY 2
—0.8  1.2—0.8  1.2—0.8  1.2—0.8  1.2µs START-UP DELAY —1025—1025—1025—1025µs 0 TO 28 VIN
OVERSHOOT 4
—200
300
—
100
600
—200
1200—
2001500
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 the point at which Vout is within regulation.
3.Input step transition time >10µs.
4.Input step transition time <100µs.
Sync  In (500 to 600 kHz) •Duty cycle 40% to 60%•Logic low 0.8 V max
•Logic high 4.5 V min, 5 V max •Referenced to input common
•If  not used, connect to input common Inhibit TTL Open Collector •Logic low (output disabled)
Logic low voltage ≤0.8 V max Inhibit pin current 4.0 mA max
•Referenced to input common •Logic high (output enabled)
Open collector or unconnected
Electrical Characteristics:25°C Tc,28 VDC Vin,100% load,radiation level O,unless otherwise specified.
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DC/DC C
ONVERTERS SMHF SERIES
SINGLE AND DUAL
15 WATT
DUAL OUTPUT MODELS SMHF2805D SMHF2812D SMHF2815D PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS OUTPUT VOLTAGE+V OUT  4.95  5.00  5.0511.8812.0012.1214.8515.0015.15
VDC
–V OUT  4.92  5.00  5.0811.8212.00121814.7815.0015.23
OUTPUT CURRENT1V IN= 16 to 40 VDC—±1.2  1.68—±0.6250.875—±0.5000.700A OUTPUT POWER1V IN= 16 to 40 VDC——12——15——15W OUTPUT RIPPLE10 kHz -2 MHz—60160—70175—70175 VOLTAGE  ±V OUT Tc = –55°C to +125°C—100240—100275—100275
mV p-p
LINE REGULATION BALANCED+V OUT—550—550—550
mV Vin = 16 to 40 VDC LOAD–V OUT——100——100——100
LOAD REGULATION BALANCED+V OUT—2050—2050—2050
mV LOAD–V OUT——150——150——150
CROSS REGULATION2NEGATIVE V OUT—67.5—36—36% INPUT VOLTAGE CONTINUOUS162840162840162840VDC NO LOAD TO FULL TRANSIENT50 msec——50——50——50V INPUT CURRENT NO LOAD—2050—2550—2550
FULL LOAD—540600—645754—638754mA
INHIBITED—612—512—512
INPUT RIPPLE10 kHz - 10 MHz—3080—4080—4080 CURRENT Tc = –55°C to +125°C—60120—55120—55120
mA p-p EFFICIENCY7577—7481—7482—% LOAD FAULT SHORT CIRCUIT3
POWER DISSIPATION—38—36—36W RECOVERY4—7.530—7.550—7.550ms STEP LOAD RESP.550% – 100% – 50%
BALANCED LOADS
TRANSIENT +V OUT–600200600–600300600–600300600
mV pk –V OUT–600150600–600100500–600100600
RECOVERY4—150500—200500—200600µs STEP LINE RESP.16 – 40 – 40 VDC
±V OUT TRANSIENT6–800600800–750550750–750550750mV pk RECOVERY4—0.8  1.2—0.8  1.2—0.8  1.2ms START-UP DELAY—1230—1225—1225ms OVERSHOOT7010050002005000200500mV pk
Notes
1.Up to 70% of the total output power is available from either output providing
the opposite output is simultaneously carrying 30% of the total output power.  Each output must carry a minimum of 30% of the total output power in order to maintain regulation on the negative outputs.
2.Effect on –Vout for the following conditions, percentages are of total power:
+Po = 50% to 10% and –Po  = 50%
+Po = 50% and –Po  = 50% to 10%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 Vout is within regulation.
5.Response of either output with the opposite output held at half of the total
output power.
6.Input step transition time >10µs.
7.Input step transition time <100µs.
Electrical Characteristics:25°C Tc,28 VDC Vin,100% load,radiation level O,unless otherwise specified.
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DC/DC C
ONVERTERS
SMHF SERIES SINGLE AND DUAL 15 WATT
BLOCK DIAGRAM
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DC/DC C ONVERTERS
SMHF SERIES
SINGLE AND DUAL
15 WATT
SMD NUMBERS
S TANDARD M ICROCIRCUIT D RAWING
(SMD)5962-9213902HXC IN PROCESS
5962-9160102HXC 5962-9555902HXC 5962-9214402HXC 5962-9161402HXC
SMHF
S IMILAR P ART
SMHF2805S/HO SMHF2812S/HO SMHF2815S/HO SMHF2805D/HO SMHF2812D/HO SMHF2815D/HP
T o indicate the flanged case option change the “X ” to “Z ” In the SMD number. The SMD number shown is for Class H screening, non-flanged, and no Radiation Hardness Assurance (RHA) level. See the SMD for the numbers for other screening and radiation levels. For exact specifications for an SMD product, refer to the SMD drawing.Call your Interpoint repre-sentative for status on the SMHF SMD releases which are “in process.”  SMDs can be downloaded from www.dscc.dla.mil/programs/smcr
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DC/DC C ONVERTERS
SMHF SERIES SINGLE AND DUAL 15 WATT
Typical Performance Curves:25°C Tc ,28 VDC Vin,100% load,free run,unless otherwise specified.
F IGURE 9
F IGURE 10F IGURE 11
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