REFRESH TIMER FOR PLURAL OPERATING VOLTAGE

摘要

The refresh timer providing the constant cycle refresh signal even though the input operating voltage is changed comprises a multiple start-up circuit (100A) connected to the power terminal; a control circuit (200A) receiving the output of the start-up circuit (100A) to produce different signals for each operating voltage; a ring oscillator (300A) generating different frequency signal according to each output signal of the control circuit (200A); a counter stage (400A) amplifying the output signal of the ring oscillator (300A) to produce the refresh cycle time signal. Only one of the ring oscillators (300A) is selected for each operating voltage to generate the constant frequency refresh signals.