EEPROM


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Related to EEPROM: flash memory

EEPROM

[¦ē′ē‚präm]

EEPROM

EEPROM

(Electrically Erasable Programmable ROM) A rewritable memory chip that holds its content without power. EEPROMs are bit or byte addressable at the write level, which means either the bit or byte must be erased before it can be re-written. In flash memory, which evolved from EEPROMs and is almost identical in architecture, an entire block of bytes must be erased before writing. In addition, EEPROMs are typically used on circuit boards to store small amounts of instructions and data, whereas flash memory modules hold gigabytes of data for digital camera storage and hard disk replacements (see flash memory).

A Floating Gate Holds the Charge
EEPROM and flash memory bit cells are CMOS-based transistors that hold a charge on a "floating gate." With no charge on the floating gate, the transistor acts normally, and a pulse on the control gate causes current to flow. When charged, it blocks the control gate action, and current does not flow. Charging is accomplished by grounding the source and drain terminals and placing sufficient voltage on the control gate tunnel through the oxide to the floating gate. A reverse voltage channeled from another transistor clears the charge by causing it to dissipate into the substrate.

EEPROMs have a lifespan of between 10K and 100K write cycles, which is considerably greater than the EPROMs (single "E") that preceded them. See EPROM, SEEPROM, memory types and flash memory.


The Floating Gate Transistor
EEPROM and flash memory cells use a transistor with a floating gate that holds a charge. When charged, the action of the control gate is impeded, and the charged/uncharged state determines the 0 or 1 content of the bit.







The Erase Circuit
The floating gate transistor stores the charge, and a regular MOS transistor is used to erase it. Most EEPROMs are byte erasable with one MOS transistor for every eight floating gate transistors. Flash memory uses only one MOS transistor to erase an entire block of floating gate transistors.
References in periodicals archive ?
With Microchip's tiny new serial EEPROMs, designers can replace larger packages with these smaller, less-expensive packages without sacrificing performance.
Tags / Keywords: EEPROM, I(2)C, Microchip, memory, stand-alone memory, MPLAB, 24VL014, 24VL014H, 24VL024, 24VL024H, 24VL025, low voltage, very low voltage, ultra low voltage, low power, half-array write protect, full-array write protect, 1.
All of the new EEPROM devices are available in 8-pin TSSOP, 2 mm x 3 mm TDFN and MSOP packages, as well as the 6-pin SOT-23 package.
The 25XX128/512 and 25XX1024 serial EEPROM devices are supported by the same development tools that support all of Microchip's memory parts.
The 25AA010A and 25LC010A EEPROMs provide 1 Kb of memory density, the 25AA020A and 25LC020A provide 2 Kb, and the 25AA040A and 25LC040A provide 4 Kb of memory density, all with capability for speeds up to 10 MHz.
The new products include an optional EEPROM write disable pin input, an interrupt output that indicates input pin level and PWM state changes, and internal power-on reset.
To help designers get started with the 24XX1025 serial EEPROMs, Microchip offers the SEEVAL(R) 32 Serial EEPROM Designer's Kit, available today at www.
Our agreement with UMC will make Aplus' leading EEPROM IP more widely available to customers targeting UMC's process technologies," said Peter Lee, CEO of Aplus.
The new SPI devices are supported by Microchip's SEEVAL(R) 32 Serial EEPROM Designer's Kit.
Catalyst supervisors with memory provide an integrated solution for designers that demand robust and reliable system operation, while providing mid-density serial EEPROM to store critical information," said Barr Karagozlu, Product Marketing.
The EEPROM process is fully automotive-qualified and eminently suited for harsh environment, making it ideal for designs in automotive, medical and industrial applications.
The new DFN package is available for Microchip's I2C serial EEPROM product family (the 24xx series) in memory densities ranging from 128 bits to 64 Kbits and an application-specific 2-Kbit device for DIMM modules.