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Fabricante

IQ18-HPC

Half-brick DC-DC Converter

SynQor Worldwide Headquarters 

Technical

Specification

IQ18-HPC Family

BASIC OPERATION AND FEATURES

This converter series 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-up or

step-down to achieve the 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 far less energy than Schottky

diodes. This is the primary reason that the converter has such

high efficiency, even at very low output voltages and very high

output currents.

These converters are offered totally encased to withstand harsh

environments and thermally demanding applications. 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.

This series of converters use 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(-).

The ON/OFF signal is active low (meaning that a low turns the

converter on). Figure A details four 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

connected 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 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.

ON/OFF

ON/OFF

Vin(_)

Vin(_)

Remote Enable Circuit

Negative 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.

Product # IQ18xxxHPCxx

Phone 1-888-567-9596

www.synqor.com

ON/OFF

Vin(_)

50k

50k

100pF

5V

TTL

Figure B: Internal ON/OFF pin circuitry

Doc.# 005-005029 Rev. B

04/13/09

Page 24

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