Technical Specification
Eighth
Brick
BASIC OPERATION AND FEATURES
The
PowerQor
series converter uses a two-stage power circuit
topology. The first stage is a buck-converter that keeps the out-
put voltage constant over variations in line, load, and temper-
ature. The second stage uses a transformer to provide the func-
tions of input/output isolation and voltage step-down to achieve
the low output voltage required.
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
PowerQor
converter 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. Since a heatsink is not
required, the
PowerQor
converter does not need a metal base-
plate or potting material to help conduct the dissipated energy
to the heatsink. The
PowerQor
converter can thus be built more
simply and reliably using high yield surface mount techniques
on a PCB substrate.
The
PowerQor
series of eighth-brick, quarter-brick and half-
brick converters uses the industry standard footprint and pin-out
configuration.
48Vin 1.5Vout 15A
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.
REMOTE SENSE(+) (Pins 7 and 5):
The SENSE(+) inputs
correct for voltage drops along the conductors that connect the
converter’s output pins to the load.
Pin 7 should be connected to Vout(+) and Pin 5 should be con-
nected to Vout(-) at the point on the board where regulation is
desired. A remote connection at the load can adjust for a volt-
age drop only as large as that specified in this datasheet, that
is
[
Vout(+) - Vout(-)
]
–
[
SENSE(+) - SENSE(-)
]
<
Sense Range % x Vout
Pins 7 and 5 must be connected for proper regulation of the
output voltage. If these connections are not made, the convert-
er will deliver an output voltage that is slightly lower than its
specified value.
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 # PQ60015EML15
Phone 1-888-567-9596
Figure B:
Internal ON/OFF pin circuitry
Doc.# 005-2EM651E Rev. B
9/3/03
Page 9
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