The CS284XA, CS384XA provides all the necessary features to implement off-line fixed frequency current-mode control with a minimum number of external components. The CS384XA family incorporates a new precision temperature-controlled oscillator with an internally trimmed discharge current to minimize variations in frequency. A precision duty-cycle clamp eliminates the need for an external oscillator when a 50% duty-cycle is used. Duty-cycles greater than 50% are also possible. On board logic ensures that VREF is stabilized before the output stage is enabled. Ion implant resistors provide tighter control of undervoltage lockout.