MCH2805S Datasheet, PDF (1/8 Pages) Interpoint Corporation Company – DC/DC CONVERTERS 28 VOLT INPUT

FEATURES
• -55°C to +125°C operation
DC/DC CONVERTERS
• 12 to 50 VDC input
• Fully isolated
28 VOLT INPUT
• Magnetic feedback
• Fixed frequency 370 kHz typ.
• Topology – Current Mode Flyback
• 80 V for up to 120 ms transient protection
(70 V for 15 V single and dual models)
• Inhibit function
• Short circuit protection
• Undervoltage lockout
Size (max.): 0.980 x 0.805 x 0.270 inches (24.89 x 20.45 x 6.86 mm)
Weight: 12 grams max.
Screening: Standard, ES, or 883 (Class H)
MCH SERIES
1.5 WATT
MODELS
VDC OUTPUT
SINGLES
5
5.2
12
15
DUALS
±5
±12
±15
DESCRIPTION
With a miniature footprint of just 0.8 square inches, the MCH
Series™ of DC/DC converters delivers 1.5 watts of output power
while saving significant board real estate. The wide input voltage
range of 12 to 50 VDC accepts the varying voltages of military, aero-
space, or space bus power and tightly regulates output voltages to
protect downstream components. Transient protection of 80 volts for
up 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 of up
to 70 volts for up to 120 milliseconds.
CONVERTER DESIGN
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. Up to 80% of the total load may be on one output
providing that the other output carries a minimum of 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 as a 10
VDC output.)
POSITIVE ¹
INPUT
INHIBIT FUNCTION
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.
PROTECTION FEATURES
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 oper-
ations. 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.
MIL-STD-461
Use Interpoint’s FMSA-461 EMI filter to pass the CE03 requirements
of MIL-STD-461C.
CONVENIENT PACKAGING
The MCH Series converters are packaged in hermetically sealed,
projection-welded metal cases which provide EMI/RFI shielding.
+ _{0.47 µF}
typical
INHIBIT ^{7 SHUTDOWN}
INPUT ²
COMMON
+V_IN
FB
PWM
CONTROLLER
+V_OUT
3 _POSITIVE
+
OUTPUT
4 _OUTPUT
+
COMMON
DUAL MODELS ONLY
6 _NEGATIVE
OUTPUT
FIGURE 1: BLOCK DIAGRAM
1