Product # PQ60120QEx25

Phone 1-888-567-9596

www.synqor.com

Doc.# 005-2QE612J Rev. G

01/14/15

Page 10

Input:

35-75V

Output:

12V

Current:

25A

Package:

Quarter-brick

Applications Section

Applications Section

BASIC OPERATION AND FEATURES

This converter series uses a two-stage power conversion topology.

The first stage 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 frequency

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

significantly less energy than Schottky diodes, enabling the

converter to achieve high efficiency.

Dissipation throughout the converter is so low that it does not

require a heatsink for operation in many applications; however,

adding a heatsink provides improved thermal derating performance

in extreme situations. To further withstand harsh environments

and thermally demanding applications, certain models are available

baseplated or totally encased. See Ordering Information page for

available thermal design options.

SynQor quarter-brick converters use the industry standard footprint

and pin-out.

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

)

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(-).

In negative logic versions, the ON/OFF signal is active low (meaning

that a low voltage turns the converter on). In positive logic versions,

the ON/OFF input is active high (meaning that a high voltage turns

the converter on). Fig A details possible circuits for driving the ON/

OFF pin. See Ordering Information page for available enable logics.

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

SENSE(-) inputs correct for voltage drops along the conductors that

connect the converter’s output pins to the load.

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

) at the point on the board where regulation is desired. 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.

OUTPUT VOLTAGE TRIM (Pin 6): The TRIM input permits the

user to adjust the output voltage across the sense leads up or down

according to the trim range specifications. SynQor uses industry

standard trim equations.

To decrease the output voltage, the user should connect a resistor

between Pin 6 (TRIM) and Pin 5 (SENSE(-) input). For a desired

decrease of the nominal output voltage, the value of the resistor

should be:

(

511%

–

10.22

Δ%

where

|

1.225

kΩ

To increase the output voltage, the user should connect a resistor

between Pin 6 (TRIM) and Pin 7 (SENSE(+) input). For a desired

increase of the nominal output voltage, the value of the resistor

should be:

The Trim Graph in Figure B shows the relationship between the

trim resistor value and Rtrim-up and Rtrim-down, showing the total

range the output voltage can be trimmed up or down.

Note: The TRIM feature does not affect the voltage at which the

output over-voltage protection circuit is triggered. Trimming the

output voltage too high may cause the over-voltage protection

circuit to engage, particularly during transients.