AS3842 DIP IC

Features
? 2.5 V bandgap reference trimmed to
1.0% and temperature-compensated
? Standard temperature range extended
to 105?C
? AS3842/3 oscillations trimmed for
precision duty cycle clamp
? AS3844/5 have exact 50% max duty
cycle clamp
? Advanced oscillator design simplifies
synchronization
? Improved specs on UVLO and
hysteresis provide more predictable
start-up and shutdown
? Improved 5 V regulator provides better
AC noise immunity
? Guaranteed performance with current
sense pulled below ground

Description
The AS3842 family of control ICs provide pin-for-pin replacement of the
industry standard UC3842 series of devices. The devices are
redesigned to provide significantly improved tolerances in power supply manufacturing. The 2.5 V reference has been trimmed to 1.0%
tolerance. The oscillator discharge current is trimmed to provide guaranteed duty cycle clamping rather than specified discharge current.
The circuit is more completely specified to guarantee all parameters
impacting power supply manufacturing tolerances.
In addition, the oscillator and flip-flop sections have been enhanced to
provide additional performance. The RT/CT pin now doubles as a synchronization input that can be easily driven from open collector/open
drain logic outputs. This sync input is a high impedance input and can
easily be used for externally clocked systems. The new flip-flop topology allows the duty cycle on the AS3844/5 to be guaranteed between
49 and 50%. The AS3843/5 requires less than 0.5 mA of start-up current over the full temperature range.