PQ60033EGX20 Datasheet, PDF (9/13 Pages) SynQor Worldwide Headquarters – Fixed frequency switching provides predictable EMI performance

Technical
Specification
PQ60033EGx20
BASIC OPERATION AND FEATURES
The PowerQor series converter uses a two-stage power conversion
topology. The first stage is a buck-converter that keeps the output
voltage constant over variations in line, load, and temperature.
The second stage uses a transformer to provide the functions 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 trans-
former’s output is accomplished with synchronous rectifiers. 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 baseplate 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 con-
figuration.
ON/OFF
ON/OFF
ON/OFF
Vin(^_)
Remote Enable Circuit
Vin(^_)
Negative Logic
(Permanently Enabled)
Vin(^_)
Positive Logic
(Permanently Enabled)
ON/OFF
5V
TTL/
CMOS
ON/OFF
Vin(^_)
Open Collector Enable Circuit
Vin(^_)
Direct Logic Drive
Figure A: Various circuits for driving the ON/OFF pin.
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 polarity of the logic
used for the ON/OFF input.
In the positive logic version, the ON/OFF input is active high
(a high turns the converter on). In the negative logic version, the
ON/OFF signal is active low (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 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 voltage
drop only as large as that specified in this datasheet, that is
[Vout(+) - Vout(-)] – [Vsense(+) - Vsense(-)] <
Sense Range % x Vout
Pins 7 and 5 must be connected for proper regulation of the out-
put voltage. If these connections are not made, the converter will
deliver an output voltage that is slightly higher than its specified
value.
Note: The output over-voltage protection circuit senses the volt-
age across the output (pins 8 and 4) to determine when it should
trigger, not the voltage across the converter’s sense leads (pins
7 and 5). Therefore, the resistive drop on the board should be
small enough so that output OVP does not trigger, even during
load transients.
5V
Vin(+)
274k
ON/OFF
50k
TTL
100pF
50k
Vin(^_)
Figure B: Internal ON/OFF pin circuitry
Product # PQ60033EGx20
Phone [phone]
www.synqor.com
Doc.# 005-0005349 Rev. A
09/23/09
Page 9