TOP242 datasheet(10/48 Pages) POWERINT

10 / 48 page

TOP242-249

7/01

August 8, 2000

also used to generate a temperature-compensated current

reference which is trimmed to accurately set the switching

frequency, MOSFET gate drive current, current limit, and the

line OV/UV thresholds. TOPSwitch-GX has improved circuitry

to maintain all of the above critical parameters within very tight

absolute and temperature tolerances.

High-Voltage Bias Current Source

This current source biases TOPSwitch-GX from the DRAIN pin

and charges the CONTROL pin external capacitance during

start-up or hysteretic operation. Hysteretic operation occurs

during auto-restart, remote off and over-temperature shutdown.

In this mode of operation, the current source is switched on and

off with an effective duty cycle of approximately 35%. This

duty cycle is determined by the ratio of CONTROL pin charge

C) and discharge currents (ICD1 and ICD2). This current source

is turned off during normal operation when the output MOSFET

is switching. The effect of the current source switching will be

seen on the DRAIN voltage waveform as small disturbances

and is normal.

TOP242 Datasheet(PDF) 10 Page - Power Integrations, Inc.