The AS2842 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 AS2844/5 to be guaranteed between 49 and 50%. The AS2843/5 requires less than 0.5 mA of start-up current over the full temperature range.
The AS2842/3/4/5 family are current‑mode controller ICs that replace the UC3842 series with tighter tolerances, a 2.5 V bandgap reference, and a synchronized oscillator. Features include a guaranteed duty‑cycle clamp, improved UVLO, and a 5 V regulator for better noise immunity.
The document lists ordering options, pin assignments, absolute maximum ratings, detailed electrical characteristics, typical performance curves, and layout recommendations for stable operation in switch‑mode power supplies.
| Operating Temperature Range | -40 to 105 °C |
|---|---|
| Bandgap Reference Tolerance | 2.5 V ±1.0 % |
| Minimum Duty Cycle | 0 % |
| Output Current (OUT pin) | up to 1 A sink/source |
| Supply Voltage (Low‑Impedance Source) | Vcc up to 30 V |
The controller is specified for operation from –40 °C to +105 °C.
The OUT pin can sink or source peak currents up to 1 A.
Pin 4 (Ri/Cr) can be pulled to ground or to Vreg to provide a synchronization function.
The AS2843/5 requires less than 0.5 mA of start‑up current over the full temperature range.