PQ50050HPB50 datasheet(10/14 Pages) SYNQOR | Output voltage trim permits custom voltages and voltage margining

10 / 14 page

Product # PQ50050HPB50

Phone 1-888-567-9596

www.synqor.com

Doc.# 005-0005487 Rev. A

03/18/10

Page 10

Input:

Output:

Current:

Part No.:

BASIC OPERATION AND FEATURES

The PowerQor series converter uses a two-stage power conversion

Power

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

Power

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 pot-

ting 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, quarter-brick and eighth-

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 ref-

erenced 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 8 and 6):

REMOTE SENSE(+) (Pins 8 and 6): The SENSE(+) inputs

The SENSE(+) inputs

correct for voltage drops along the conductors that connect the

converter’s output pins to the load.

Pin 8 should be connected to Vout(+) and Pin 6 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 8 and 6 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 speci-

fied value.

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

across the output (pins 9 and 5) to determine when it should trig-

ger, not the voltage across the converter’s sense leads (pins 8 and

6). 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.

TTL

ON/OFF

Vin(_)

Vin(+

in(

in( )

50k

274k

50k

100pF

Open Collector Enable Circuit

Remote Enable Circuit

Direct Logic Drive

Negative Logic

(Permanently

Enabled)

(Permanently

Enabled)

ON/OFF

Vin(_

)

ON/OFF

Vin(_

)

ON/OFF

TTL/

CMOS

Vin(_

)

Vin(_

)

Positive Logic

ON/OFF

Vin(_

)

Figure B: Internal ON/OFF pin circuitry

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