a release of a short-circuit condition, or 3) a release of a cur-

rent limit condition. Load capacitance determines exactly how

high the output voltage will rise in response to these conditions.

After 200 ms the converter will automatically restart.

Over-Temperature Shutdown: A temperature sensor on

the converter senses the average temperature of the module.

The thermal shutdown circuit is designed to turn the converter

off when the temperature at the sensed location reaches the

Over-Temperature Shutdown value. It will allow the converter to

turn on again when the temperature of the sensed location falls

by the amount of the Over-Temperature Shutdown Restart

Hysteresis value.

APPLICATION CONSIDERATIONS

Input System Instability: This condition can occur

because any DC/DC converter appears incrementally as a

negative resistance load. A detailed application note titled

“Input System Instability” is available on the SynQor web site

(www.synqor.com) which provides an understanding of why

this instability arises, and shows the preferred solution for cor-

recting it.

Application Circuits: Figure D below provides a typical cir-

cuit diagram which details the input filtering and voltage trim-

ming.

Input Filtering and External Capacitance: Figure E

below provides a diagram showing the internal input filter com-

ponents. This filter dramatically reduces input terminal ripple

current, which otherwise could exceed the rating of an external

electrolytic input capacitor. The recommended external input

capacitance is specified in the “Input Characterisitcs” section.

More detailed information is available in the application note

titled “EMI Characteristics” on the SynQor website.

Product # PQ48015HKA20

Phone 1-888-567-9596

Doc.# 005-2HK451G Rev. C

4/9/03

Page 11

Half

Half

Brick

Brick

Technical Specification

48Vin 1.5Vout 20A

External

Input

Filter

Trim

L

or

ON/OFF

Electrolytic

Capacitor

33µF

ESR

≅1Ω

Figure D: Typical application circuit (negative logic unit, permanently enabled).