TOP242 Power Integrations Inc., TOP242 Datasheet - Page 10

• Manufacturer Part Number: TOP242
• Description: Family Extended Power/ Design Flexible/Integrated Off-line Switcher
• Manufacturer: Power Integrations Inc.

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
(I
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.
10
C
) and discharge currents (I
TOP242-249
E
7/01
August 8, 2000
CD1
and I
CD2
). This current source