Technical Specification
Brick Dual
48Vin 3.3/2.5Vout 87W
BASIC OPERATION AND FEATURES
The
DualQor
series converter uses a two-stage power circuit
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
output 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 recti-
fiers. These devices, which are MOSFETs with a very low on-
state resistance, 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
are available for optional heatsinking in severe thermal envi-
ronments.
The
DualQor
series converter uses the industry standard foot-
print and pin-out configuration.
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)
Quarter
CONTROL FEATURES
REMOTE ON/OFF (Pin 2):
The ON/OFF input, Pin 2, per-
mits 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 cir-
cuits for driving the ON/OFF pin. Figure B is a detailed look of
the internal 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 propor-
tionally. 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
following table shows the resistor values needed to trim the out-
put voltage up or down.
Vo(%)
1
2
3
4
5
6
7
8
9
10
R
up
46.4 20.5 12.1 8.06 5.23 3.57 2.21 1.30 0.604 0
R
down
57.6 25.5 14.0 8.87 5.90 3.83 2.32 1.30 0.432 0
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 # DQ63325QGL09
Phone 1-888-567-9596
Figure B:
Internal ON/OFF pin circuitry
Doc.# 005-2DQ632D Rev. B
10/7/03
Page 11
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