MODELS

B2-47

SINGLE

5

12

15

18

DUAL

±5

±12

±15

DESCRIPTION

The MHD Series™ of DC/DC converters offers up to 20 watts of

output power over the full military temperature range with up to 84%

efficiency. Thick-film hybrid techniques provide military/aerospace

reliability levels and optimum miniaturization. The MHD Series

MHD converters are packaged in hermetically sealed metal cases,

making them ideal for use in military, aerospace and other high reli-

ability applications. Units are available with standard screening,

“ES” screening, or fully compliant SMD versions (see Section C2 for

screening conditions).

The MHD converters are constant frequency, pulse-width mod-

ulated switching regulators which use a quasi-square wave, single

ended, forward converter design. Tight load regulation (5 mV

typical) is maintained via wide bandwidth magnetic feedback and,

on single output models, through use of remote sense. On dual

output models, the positive output is independently regulated and

the negative output is cross regulated through the use of tightly

coupled magnetics and shunt regulators.

Indefinite short circuit protection and overload protection are

provided by a constant current-limit feature. This protective system

senses current in the converter’s secondary stage and limits it to

approximately 115% of the maximum rated output current.

MHD converters are provided with internal filtering capacitors that

help reduce the need for external components in normal operation.

For systems that require compliance with MIL-STD-461C’s CE03

standard, Interpoint offers filter/transient suppression modules

(including the FMC-461, FMD-461 and FM-704A series filters) which

will result in compliance. Contact your Interpoint representative for

further details.

The MHD offers a synchronization feature that allows the designer

to match the switching frequency of the converter to the frequency

of the system clock. In free-run (unsynchronized) mode, the MHD

unit switches at 625 kHz (nominal). In sync mode, the converter will

run at any frequency between 500 kHz and 675 kHz. The sync

control operates with a quasi-TTL signal at any duty cycle between

40% and 60%.

Synchronizing the converter with the system clock allows the

designer to confine switching noise to clock transitions, minimizing

interference and reducing the need for filtering. The sync pin should

be connected to input common pin when not in use.

The MHD converters are designed to provide full power operation

over a full 16 to 40 VDC voltage range. Operation below 16 volts,

including MIL-STD-704E emergency power conditions is possible

with derated power. Refer to the low line dropout graph (Figure 15)

for details.

The MHD feed-forward compensation system provides excellent

dynamic response and noise rejection. Audio rejection is typically 50

dB. The min. to maximum step line transient response is typically

less than 4%.

MHD 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 V) 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 9 to 11 V. In the inhibit mode, a maximum of 8 mA must be sunk

from the inhibit pin.

MHD SERIES

20 WATT

• –55° to +125°C operation

• 16 to 40 VDC input

• Fully Isolated

• Magnetic feedback

• Fixed frequency

• Topology – Single Ended Forward

• 50 V for up to 50 ms

transient protection

• Inhibit and synchronization functions

• Indefinite short circuit protection

Size (max.): Non-flanged, case H2

2.125 x 1.125 x 0.400 inches (53.98 x 28.58 x 10.16 mm)

Flanged case, K3

2.910 x 1.125 x 0.400 inches (73.91 x 28.58 x 10.16 mm)

See Section B8, cases H2 and K3 for dimensions.

Weight:

52 grams max., flanged 55 grams max.

Screening:

Standard, ES, or 883 (Class H). See Section C2 for screening

options, see Section A5 for ordering information.