EEPROM

EEPROM stands for Electrically Erasable Programmable Read-Only Memory. It is a non-volatile memory that retains stored data without power and can be both programmed and erased using electrical signals. Unlike static RAM or conventional PROM, EEPROM allows data to be updated in place, typically at the byte level, though some devices support small page-sized operations.

Most EEPROM devices use floating-gate transistor technology. The stored data corresponds to the presence or absence of charge on a floating gate, which shifts the transistor’s threshold voltage. Erasing removes this charge, allowing reprogramming. Erase and program operations usually require higher voltages or specialized circuitry; newer devices may use tunneling techniques to enable low-voltage operation. EEPROM is distinct from EPROM, which requires ultraviolet light to erase, and from PROM, which is not intended to be rewritten. Flash memory is a related form that erases in larger blocks rather than individual bytes.

Types include serial EEPROMs (I2C or SPI interfaces) and traditional parallel EEPROMs. Serial devices are common in microcontroller applications for storing configuration data and small data sets; they typically support byte writes and small page writes. Endurance is commonly tens of thousands to hundreds of thousands of write/erase cycles per cell, with data retention typically rated in years to decades.

Applications include saving device configuration, calibration data, and small firmware parameters that must survive power loss. Because EEPROM tends to be slower and more expensive per bit than flash, it is usually used for small data stores rather than bulk storage. In many systems it sits alongside flash memory or battery-backed RAM for critical parameters.