A stable programming pulse generator for single power supply flash memories

A stable programming pulse generator has been developed for single power supply, high-speed programming, and low-power flash memories. The newly developed delay circuit operates by amplifying the difference between the reference voltage and the capacitor voltage raised by the charging current which is proportional to the reference voltage. Linearity between the capacitor voltage swing and the driving current enables us to make the delay circuit supply voltage-, temperature-, and process-tolerant. Thus, the proposed delay circuit stably controls a programming pulse width through all operational ranges of supply voltage and temperature. The output frequency of the newly developed oscillator is inversely proportional to the supply voltage. This oscillator stably drives charge pump circuits which generate high programming voltages on chip since dependence of charge pump characteristics on frequency and supply voltage can be cancelled. As a result, the programming pulse generator including the delay circuit and the oscillator has reduced the total programming time under the slowest condition, i.e., high temperature and low voltage condition, by 30% and the power consumption under the fastest condition, i.e., low temperature and high voltage condition, by 20%, for a 3.3 V-only flash memory.