AS3842

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 sup-ply manufacturing. The 2.5 V reference has been trimmed to 1.0% tolerance. The oscillator discharge current is trimmed to provide guar-anteed 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 R_T /C_T pin now doubles as a syn-chronization 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 topol-ogy 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 cur-rent over the full temperature range.