WORDLINE DRIVER FOR FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM)

摘要

A flash Electrically-Erasable Programmable Read-Only Memory (EEPROM) (10) includes a plurality of floating gate transistor memory cells (32), a plurality of wordlines (WL) connected to the cells (32) and a power source (13) for generating a low power supply voltage on the order of 3 V or less. A wordline driver (50) includes a booster (52) for boosting the supply voltage to produce a wordline read voltage which is higher than the supply voltage, and applying the wordline voltage to a wordline. An upper clamp (54) limits a maximum value of the wordline voltage to prevent read disturb. The upper clamp (54) can be configured to reduce an amount by which the maximum value varies with the supply voltage, or to limit the maximum value to substantially a predetermined value. A lower clamp (56) limits the wordline voltage to a minimum value which is higher than the supply voltage and lower than the maximum value for a predetermined length of time at the begining of the read operation to ensure that the cells (32) have sufficient read current and to reduce the amount by which the minimum value varies with the supply voltage.