Terminology » EPROM vs EEPROM vs Flash EPROM: Key Differences Explained

EPROM vs EEPROM vs Flash EPROM: Key Differences Explained

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This page outlines the key differences between various types of Erasable Programmable Read-Only Memory (EPROM), specifically EPROM, Electrically Erasable PROM (EEPROM), and Flash EPROM. These are all re-programmable memory types commonly used in processor-based systems. Like EPROMs, an EEPROM device is programmed by applying a high voltage to the control gate.

SpecificationsEPROMEEPROMFlash EPROM
Relative Size of Cell131.2 to 1.3
ProgrammingBy external MeansInternalInternal
Programming TechniqueHot electron injectionTunnel effectHot electron injection
Voltage12.5 V5 V12 V
ResolutionByteByteByte
Time taken< 100 µS5 ms< 10 µS
ErasingBy external meansInternalInternal
Erasing TechniqueUltraviolet lightTunnel effectTunnel effect
ResolutionWhole chipByteWhole chip or block
Time Taken15 min5 ms1 sec

Key Differences Summarized

The table above highlights the core differences:

  • Cell Size: EEPROM cells are generally larger than EPROM and Flash EPROM cells.

  • Programming: EPROMs require external equipment for programming, while EEPROMs and Flash EPROMs can be programmed internally.

  • Programming Technique: Both EPROM and Flash EPROM utilize hot electron injection for programming, while EEPROM uses the tunnel effect.

  • Voltage: The required programming voltages vary across the three types.

  • Erasing: EPROMs are erased using ultraviolet light, requiring the entire chip to be erased at once. EEPROMs and Flash EPROMs use electrical signals (tunnel effect) for erasing.

  • Erasing Granularity: EEPROMs can erase individual bytes, while Flash EPROMs typically erase entire blocks or the whole chip. This difference impacts the speed and flexibility of data updates.

  • Erasing Time: EPROMs take significantly longer to erase than EEPROMs and Flash EPROMs due to the UV light erasure method.