F
EATURES
鈥?鈥?0擄C to +85擄C operation
鈥?16 to 40 VDC input
(19 to 40 VDC input for
15 volt output models)
鈥?Fully Isolated
鈥?Optocoupler feedback
鈥?600 kHz typical operating frequency
鈥?Topology 鈥?Single Ended Forward
鈥?50 V for up to 50 ms transient protection
鈥?Inhibit function
鈥?Indefinite short circuit protection
鈥?Up to 83% efficiency
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
HR120 SERIES
12 WATT
MODELS
VDC O
UTPUT
SINGLE
5
12
15
DUAL
鹵12
鹵15
Size (max.): 1.460 x 1.130 x 0.330 inches (37.08 x 28.70 x 8.38 mm)
See Section B8, case E1 for dimensions.
Weight:
21 grams typical.
Screening: Standard only. See Section C2 for screening description.
DESCRIPTION
The HR120 Series鈩?of DC/DC converters offers up to 12 watts of
power from single or dual outputs in a single package over a 鈥?0擄C
to +85擄C temperature range. Thick film hybrid manufacturing tech-
nology produces high levels of miniaturization, giving the HR120
Series converters a low profile (0.330 inch), small board area (1.65
square inches), and high power density (22 watt/in
3
).
The parts are packaged in sealed steel enclosures, making them
ideal for use in high reliability applications. Each unit is guaranteed
to pass a hermeticity test with a maximum leak rate of 0.001 atm-
cc/sec.
Indefinite short circuit protection and overload protection are
provided by sensing output load current and restricting the output
current to approximately 125% of full load output current. Since the
output current is sensed in the secondary stage, the result is a
predictable, constant output current control with no foldback char-
acteristics. HR120 converters are provided with internal filtering
elements on both the input and output to help reduce the need for
external components.
W
IDE
V
OLTAGE
R
ANGE
The 5 and 12 volt output models provide full power operation over
the input voltage range of 16 to 40 volts (19 to 40 volts for 15 volt
output models). Operation below 16 volts (or below 19 volts for the
15 volt output models), including operation in MIL-STD-704E emer-
gency power conditions, is possible with derated output power.
Please refer to the low voltage drop-out graphs, Figures 9 and 10.
The HR120 Series provides full power operation at case tempera-
tures from 鈥?0擄C up to +85擄C. Depending on operating levels, air
flow, and ambient temperature, heat sinking may be required.
D
ESIGN
M
ETHODOLOGY
The HR120 converters are switching regulators which use a quasi-
square wave, single ended forward converter design with a nominal
switching frequency of 600 kHz. Isolation between input and output
circuits is provided with a transformer in the forward power loop and
a temperature insensitive optical link in the feedback control loop.
Output regulation is accomplished with constant frequency pulse
width modulation. Both line and load regulation are typically within
10 mV.
On dual output models, the positive output is independently regu-
lated and the negative output is cross-regulated. Figures 7 and 8
illustrate what effects load changes have on the negative output.
I
NHIBIT
F
EATURE
An inhibit terminal is provided that can be used to disable internal
switching, resulting in a very low quiescent input current. An open
collector TTL compatible low (鈮?.8 V) is required to control the
inhibit function. This level may be supplied by an open collector gate
since the inhibit pin is provided with an internal pull-up resistor.
B4-47
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5
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