1

Size (max.): Non flanged 1.460 x 1.130 x 0.330 (37.08 x 28.70 x 8.38 mm)

Flanged 2.005 x 1.130 x 0.330 (50.93 x 28.70 x 8.38 mm)

Weight:

30 grams maximum.

Screening: Standard, ES, or 883 (Class H).

DESCRIPTION

The MHF+ Series™ of high frequency 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 tran-

sients up to 50 volts. The package is a hermetically sealed, welded

metal case. Flanged and non-flanged models are available.

The MHF+ 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 optical link in the feedback control loop.

For the MHF+ dual output models, good cross regulation is main-

tained by tightly coupled output magnetics. Up to 90% of the total

output power (80% on 2805D) is available from either output,

providing the opposite output is simultaneously carrying 10% of the

total output power (20% on 2805D models). Predictable current limit

is accomplished by directly monitoring the output load current and

providing a constant current output above the overload point.

The MHF+ Series offers a new standard of performance for small

size and high power density. At just 0.33 inch high and a total foot-

of up to 28 watts per cubic inch.

The MHF+ 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 .

MHF+ 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 V. In the inhibit mode, a maximum of 4 mA must be sunk

from the inhibit pin.

A synchronization feature is included with the MHF+ 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 550

kHz 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.

MHF+ 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.

Undervoltage lockout prevents the units from operating below

approximately 12 VDC input voltage to keep system current levels

smooth, especially during initialization or re-start operations.

MHF+ SERIES

SINGLE & DUAL

15 WATT

• –55° to +125°C operation

• 16 to 40 VDC input

• Fully isolated

• Optocoupler feedback

• Fixed frequency, 550 kHz typical

• Topology – Single Ended Forward

• 50 V for up to 50 ms transient protection

• Inhibit and sync functions

• Indefinite short circuit protection

• Undervoltage lockout

MODELS

SINGLE

3.3

5

5.2

12

15

28

DUAL

±5

±12

±15