Technical Specification
BASIC OPERATION AND FEATURES
The
DualQor
series converter uses a two-stage power conversion
topology in which the two output voltages are cross regulated.
The first stage is a buck-converter that keeps the output voltage
constant over variations in line, load, and temperature. The sec-
ond stage uses a transformer to provide the functions of
input/output isolation and voltage step-down to achieve the low
output voltage required.
The two-stage solution is ideal for converters with multiple cross-
regulated output voltages. The first-stage compensates for any
variations in line voltage. Therefore, the dependence of the out-
put voltage on line variations is minimized.
Both the first stage and the second stage switch at a fixed fre-
quency for predictable EMI performance. Rectification of the
transformer’s output is accomplished with synchronous rectifiers.
These devices, which are MOSFETs with a very low on-state resis-
tance, dissipate far less energy than Schottky diodes. This is the
primary reason that the
DualQor
series of converters has such
high efficiency, even at very low output voltages and very high
output currents.
Dissipation throughout the converter is so low that it does not
require a heatsink for operation.
However, baseplated versions
Input:
Outputs:
Current:
Package:
35-75V
5.0V & 3.3V
40W
Quarter-brick
The
DualQor
has many standard control and protection fea-
tures. All shutdown features are non-latching, meaning that
the converter shuts off for 200 ms before restarting. (See
Figure F)
CONTROL FEATURES
REMOTE ON/OFF (Pin 2):
The ON/OFF input, Pin 2, permits
the user to control when the converter is
on
or
off.
This input is
referenced to the return terminal of the input bus,
Vin(-). There
are two versions of the converter that differ by the sense of the
logic used for the ON/OFF input.
In the positive logic version, the ON/OFF input is active high
(meaning that a high turns the converter
on).
In the negative logic
version, the ON/OFF signal is active low (meaning that a low
turns the converter
on).
Figure A details five possible circuits for
driving the ON/OFF pin. Figure B is a detailed look of the inter-
nal ON/OFF circuitry.
OUTPUT VOLTAGE TRIM (Pin 6):
The TRIM input permits the
user to adjust the output voltage up or down according to the trim
range specifications. It is important to recognize that adjusting
one output will also adjust the second output proportionally. To
lower the output voltage, the user should connect a resistor
between Pin 6 and Pin 4. To raise the output voltage, the user
should connect a resistor between Pin 6 and Pin 5. The follow-
ing table shows the resistor values needed to trim the output volt-
Vo(%)
R
up
R
down
1
50
67
2
23
30
3
14
17
4
5
6
7
8
9
9.2 6.4 4.5 3.1 2.1 1.3
11 7.8 5.4 3.7 2.4 1.4
10
0
0
are available for optional heatsinking in severe thermal envi-
ronments.
The
DualQor
series converter uses the industry standard foot-
print and pin-out configuration.
ON/OFF
ON/OFF
ON/OFF
Vin(_
)
Remote Enable Circuit
Vin(_
)
Negative Logic
(Permanently Enabled)
ON/OFF
TTL/
CMOS
Vin(_)
Positive Logic
(Permanently Enabled)
V
in(+)
274k
ON/OFF
50k
5V
5V
ON/OFF
TTL
100pF
50k
Vin(_
)
Open Collector Enable Circuit
Vin(_
)
Direct Logic Drive
V
in(
_
)
Figure A:
Various circuits for driving the ON/OFF pin.
Product # DQ65033QKA04
Phone 1-888-567-9596
Figure B:
Internal ON/OFF pin circuitry
Doc.# 005-2DQ653L Rev. B
11/11/04
Page 12
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