SMHF

FEATURES • • • • • • • • • • • • • • Fully qualified to Class H or K Radiation hardened –55° to +125°C operation 16 to 40 VDC input Fully Isolated Red hard optocoupler feedback MODELS Fixed frequency, 550 kHz typical VDC OUTPUT Topology – Single Ended Forward SINGLE DUAL Transient protection 50 V/120 ms 3.3 ±5 Inhibit function 5 ±12 Sync function 12 ±15 15 Indefinite short circuit protection Undervoltage lockout Size (max.): Non flanged 1.460 x 1.130 x 0.330 (37.08 x 28.70 x 8.38 mm) Up to 84% efficiency Flanged 2.005 x 1.130 x 0.330 (50.93 x 28.70 x 8.38 mm) See Figures 21 through 24 for dimensions. Weight: 30 grams maximum. Screening: Standard, Class H, or Class K (MIL-PRF-38534) Radiation hardness levels O, L, and R DC/DC CONVERTERS 28 VOLT INPUT SMHF SERIES SINGLE AND DUAL 15 WATT 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 50 volts. The package is a hermetically sealed, seam-welded metal case. Flanged and non-flanged models are available. 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 . INHIBIT FUNCTION SMHF converters provide an inhibit terminal that can be used to disable internal switching, resulting in no output and very low quiescent 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. SCREENING AND REPORTS 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. CONVERTER DESIGN The SMHF converters are switching regulators that use a quasisquare 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. SYNCHRONIZATION 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. SHORT CIRCUIT PROTECTION 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. HIGHER POWER DENSITY 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 footprint of 1.7 in2, this low profile package offers a total power density of up to 30 watts per cubic inch. UNDERVOLTAGE LOCKOUT 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. LOW NOISE, HIGH AUDIO REJECTION 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% 33 SMHF SERIES SINGLE AND DUAL 15 WATT DC/DC CONVERTERS SYNC AND INHIBIT 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 ABSOLUTE MAXIMUM RATINGS Input Voltage • 16 to 40 VDC Power Dissipation (Pd) • 8W 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 TYPICAL CHARACTERISTICS Output Voltage Temperature Coefficient • 100 ppm /°C typical • 150 ppm/°C maximum Input to Output Capacitance • 60 pF typical 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 RECOMMENDED OPERATING CONDITIONS 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 Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, radiation level O, unless otherwise specified. SINGLE OUTPUT MODELS OUTPUT VOLTAGE Tc = 25°C OUTPUT CURRENT VIN = 16 TO 40 VDC OUTPUT POWER OUTPUT RIPPLE VOLTAGE LINE REGULATION LOAD REGULATION INPUT VOLTAGE NO LOAD TO FULL INPUT CURRENT VIN = 16 TO 40 VDC 10 kHz - 2 MHz Tc = –55°C TO +125°C VIN = 16 TO 40 VDC NO LOAD TO FULL CONTINUOUS TRANSIENT 120 ms NO LOAD FULL LOAD INHIBITED 10k Hz - 10 MHz Tc = –55°C TO +125°C Tc = 25°C SHORT CIRCUIT POWER DISSIPATION RECOVERY2 50 %–100%– 50% TRANSIENT RECOVERY2 16 TO 40 TO 16 VIN TRANSIENT3 RECOVERY2 DELAY OVERSHOOT4 SMHF283R3S 3.27 3.3 3.33 — — 2.4 0 — — — — 16 0 — — — — — 70 — — — 60 80 5 20 28 — 25 — 5 45 — 73 5 7.5 8 160 240 100 50 40 50 65 397 12 80 120 — 8 30 500 300 800 1.2 25 300 SMHF2805S SMHF2812S SMHF2815S 4.95 5 5.05 11.88 12 12.12 14.85 15 15.15 — — 2.4 — — 1.25 — — 1.00 0 — — — — 16 0 — — — — — 73 — — –500 — –800 — — — — 30 150 5 20 28 — 25 560 5 35 — 75 3.5 7.5 150 150 550 0.8 10 100 12 80 240 100 50 40 50 40 624 12 80 120 — 8 30 500 300 800 1.2 25 600 0 — — — — 16 0 — — — — — 78 — — — 60 50 5 20 28 — 25 680 5 35 — 79 3.5 7.5 15 160 120 100 50 40 50 50 752 12 80 120 — 8 30 700 500 0 — — — — 16 0 — — — — — 74 — — –800 — — 60 100 5 20 28 — 25 670 5 35 — 80 3.5 7.5 15 75 260 100 50 40 50 62 752 12 80 120 — 7 30 VDC A W mV p-p mV mV VDC V mA INPUT RIPPLE CURRENT EFFICIENCY LOAD FAULT1 mA p-p % W ms mV pk µs mV pk µs µs mV pk STEP LOAD RESPONSE STEP LINE RESPONSE START-UP 0 TO 28 VIN –400 150 — 150 –800 550 — 0.8 — 10 — 200 –700 150 — 150 –800 550 — 0.8 — 10 — 200 200 800 600 1200 550 800 0.8 1.2 10 25 200 1500 800 –800 1.2 — 25 — 1200 — 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 10µs. 7. Input step transition time