|Category||Power Management => DC-DC Converters|
|Datasheet||Download MCH2805D datasheet
to +125°C operation to 50 VDC input Fully isolated Magnetic feedback Fixed frequency 370 kHz typ. Topology Current Mode Flyback 80 V for 120 ms transient protection (70 V for 15 V single and dual models) Inhibit function Short circuit protection Undervoltage lockout
Size (max.): x 0.270 inches x 6.86 mm) Weight: 12 grams max. Screening: Standard, ES, or 883 (Class H)DESCRIPTION
With a miniature footprint of just 0.8 square inches, the MCH SeriesTM of DC/DC converters delivers 1.5 watts of output power while saving significant board real estate. The wide input voltage range to 50 VDC accepts the varying voltages of military, aerospace, or space bus power and tightly regulates output voltages to protect downstream components. Transient protection of 80 volts for to 120 milliseconds exceeds the requirements of MIL-STD-704A for the 5, 5.2, and 12 volt single models and the 12 volt dual model. The 15 volt single and dual converters will withstand transients to 70 volts for to 120 milliseconds.
When an open collector TTL logic low is applied to the inhibit terminal, pin 7, the converter shuts down and lowers the output voltage to near zero and input current to as low as 2.3 mA. Leaving the terminal open or applying an open collector TTL logic high will enable the converter.
Undervoltage lockout prevents the MCH Series converters from operating below approximately 8 VDC input voltage to keep system current levels smooth, especially during initialization or re-start operations. All models include a soft-start function to prevent large current draw and minimize overshoot. The converters also provide short circuit protection by restricting the current.
MCH Series DC/DC converters incorporate a continuous flyback topology with a constant switching frequency of approximately 370 kHz. Current-mode pulse width modulation (PWM) provides output voltage regulation. Output error voltage is magnetically fed back to the input side of the PWM to regulate output voltage. Regulation is also affected by the load; refer to the Electrical Characteristics tables on the following pages. Dual models regulate the negative output with magnetic coupling to the positive output. 80% of the total load may be on one output providing that the other output carries a minimum 20% of the total load. The dual models can be used at double the output voltage by connecting the load between positive and negative outputs, leaving the common unconnected. (ex: MCH2805D can be used a 10 VDC output.)
The MCH Series converters are packaged in hermetically sealed, projection-welded metal cases which provide EMI/RFI shielding.PWM CONTROLLER +VOUT + 4 OUTPUT COMMON 6 NEGATIVE OUTPUT DUAL MODELS ONLY
Input Voltage to 50 VDC Output Power 1.5 W Capacitive Load Single output models 200 µF Dual output models 100 µF Lead Soldering Temperature (10 sec per lead) 300°C Storage Temperature Range (Case) to +150°C
Inhibit TTL Open Collector Logic low (output disabled) 0.8 V max Inhibit pin current 1 mA max Referenced to input common Logic high (output enabled) open collector
Output Voltage Temperature Coefficient 100 ppm/°C typical Input to Output Capacitance 170 pF typical Undervoltage Lockout 8 V input typical Current Limit 125% of full load typical Isolation 100 megohm minimum 500 V Audio Rejection 40 dB, typical Conversion Frequency (kHz) 25°C, 300 min, 370 typ, 450 max +125°C 270 min, 370 typ, 470 max Inhibit Pin Voltage (unit enabled) 12 V
Input Voltage Range to 50 VDC continuous 80 V for 120 msec transient (70 V for 15 V single and dual models) Case Operating Temperature (Tc) to +125°C full power to +135°C absolute Derating Output Power/Current (Tc) Linearly from at 135°CElectrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, unless otherwise specified.
INPUT VOLTAGE NO LOAD TO FULL INPUT CURRENT
DUAL OUTPUT MODELS PARAMETER 1 OUTPUT VOLTAGE OUTPUT CURRENT6 OUTPUT POWER OUTPUT RIPPLE VOLTAGE +VOUT VINPUT RIPPLE CURRENT EFFICIENCY LOAD FAULT
POWER DISSIPATION TO +125°C RECOVERY TO +125°C STEP LOAD %100% 50% LOAD 5 TRANSIENT RESPONSE ± VOUT TO +125°C RECOVERY TO +125°C STEP LINE TO 12 VIN RESPONSE5 ± VOUT TRANSIENT TO +125°C RECOVERY TO +125°C STARTUP DELAY TO 28 VDC, ± VOUT TO +125°C OVERSHOOT TO +125°C
Notes: 1. Specified at 50% load. 2. Lin = 2 µH. 3. Maximum duration of short circuit: 25°C- 90 seconds, 30 seconds. 4. Load fault is a short circuit (<50 mohms). Recovery is into resistive full load. 5. Transition 10 µs. Recovery = time to settle to within 1% of Vout final value.
6. Max. spec indicates 80% of the converter's total power, available from either output. 7. Specification applies to both + and Vout. 8. Although no minimum load is required, at no load the output voltage may increase to 15%.
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