Technical Specification

Product # PQ50090QGB11

Phone 1-888-567-9596

www.synqor.com

Doc.# 005-0005485 Rev. A

03/29/10

Page 9

Application Section

Open Collector Enable Circuit

Remote Enable Circuit

Direct Logic Drive

Negative Logic

(Permanently

Enabled)

(Permanently

Enabled)

ON/OFF

)

ON/OFF

ON/OFF

)

ON/OFF

5V

TTL/

CMOS

)

)

Positive Logic

ON/OFF

)

BASIC OPERATION AND FEATURES

The PowerQor series converter uses a two-stage power conver-

sion topology. The first stage is a buck-converter that keeps the

output voltage constant over variations in line, load, and tempera-

ture. 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

transformer’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 half-brick and quarter-brick converters

uses the industry standard footprint and pin-out configuration.

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 internal ON/

OFF circuitry.

REMOTE SENSE(+) (Pins 7 and 5): The SENSE(+) inputs cor-

rect for voltage drops along the conductors that connect the con-

verter’s output pins to the load.

Pin 7 should be connected to Vout(+) and Pin 5 should be connect-

ed 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

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 converter will deliver

an output voltage that is slightly higher than its specified value.

Note: the output over-voltage protection circuit senses the voltage

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.

Figure A: Various circuits for driving the ON/OFF pin.

Figure B: Internal ON/OFF pin circuitry

TTL

5V

50k

162k

ON/OFF

100k