• –40° to +85°C operation
• 18 to 36 VDC input
(19 to 36 VDC input HR301-2805)
• Fully Isolated
• Optocoupler feedback
• Fixed frequency, 240 to 300 kHz typical
• Topology – Push-Pull Forward
• 50 V for up to 50 ms transient protection
• Inhibit function
• Indefinite short circuit protection
• Remote sense on HR301-2805 model
• Up to 86% efficiency
Size (max.): 2.720 x 1.350 x 0.505 inches (69.09 x 34.29 x 12.83 mm)
See Section B8, case J5, for dimensions.
60 grams max.
Screening: Standard only. See Section C2 for screening description.
HR300 Series™ DC/DC converters combine the small size and high
reliability of hybrid-based components, the high efficiency of
switching regulators, and the isolation, regulation, and low noise
characteristics of linear regulators.
HR300 DC/DC converters use thick-film hybrid manufacturing tech-
niques for smaller size, lighter weight and higher reliability than
converters produced with other circuit techniques. With a footprint of
less than 3.7 square inches and a 0.5 inch height, the HR300
converters reach power densities up to 22 watts per cubic inch.
The HR300 parts use the same manufacturing procedures and
quality controls that Interpoint applies to converters built for aero-
space and military applications. The converters are hermetically
sealed in metal packages that are guaranteed a maximum leak rate
of less than 10
Short circuit protection is provided through foldback current limiting.
When the output current reaches approximately 125% of the full
rated load, the output voltage begins to reduce to protect the
converter. The converter can sustain a true short circuit condition
indefinitely. The HR300’s flanged case facilitates removal of heat
and provides for mechanically secure mounting. If full power opera-
tion or indefinite short circuit protection is a system requirement, the
HR300 converter should be mounted with an efficient heat sink in
contact with the mounting flange.
Internal filters in all HR300 converters provide low noise on both
the input and outputs. On HR301 models, two-section
L-C filters limit output ripple voltage and reflected input ripple
current. On HR302 models, single-section L-C filters perform the
For maximum output regulation, the HR301-2805 is provided with
external output voltage remote sense pins. Connecting the remote
sense pins to the load provides a four-terminal voltage mode which
eliminates the adverse effects of line resistance voltage drops.
Remote sense pins may be left unconnected, but see cautions in
this data sheet. For normal operation, remote sense pins should be
connected to the respective output pins.
HR300 converters use a constant frequency pulse-width modulated
switching regulator design operating in the forward mode with a
clock switching frequency of 240 to 300 kHz. Isolation is achieved
through the use of a transformer in the forward power circuit and an
optocoupler in the feedback control loop. The full load output power
of 30 watts is available over the entire 18 to 36 VDC input range (19
to 36 HR301-2805). On dual output models, up to 90% of full power
is available from either output up to a combined total of 30 watts.
The HR300’s high efficiency is maintained over the entire input
voltage range and from approximately 25% of full load to full load
(see typical efficiency curves).
An inhibit is provided to allow a logic input to shut down the
converter. An open circuit on the inhibit pin (pin 2 or 8) allows normal
operation. A connection between the inhibit pin and the input
common (pin 10) disables the internal oscillator, shutting down the
output. The inhibit pin has an open circuit voltage of 11 to 16 V on
single output models, 8 to 12 V on HR302-2812 and 10 to 14 V on
HR302-2815. In the inhibit mode, approximately 1 mA must be sunk
from the inhibit pin. An active low open collector is required to acti-
vate the inhibit function.
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