EEPROM

What Is EEPROM?

EEPROMEEPROMNon-volatile memory technology retaining data without powerView full → (Electrically Erasable Programmable Read-Only Memory) is the non-volatile memory technology used in virtually all NFC tagNFC tagPassive unpowered device storing data, powered by reader's RF fieldView full → chips. Unlike volatile memory that loses contents when power is removed, EEPROM retains stored data indefinitely without any battery or external power — a characteristic fundamental to NFC's value proposition.

How EEPROM Works

EEPROM stores data using floating-gate transistors. Each cell has a MOSFET with an additional "floating gate" surrounded by insulating oxide:

• Programming (writing a 0): A high voltage pulse forces electrons onto the floating gate via Fowler-Nordheim tunneling.
• Erasing (writing a 1): A reverse voltage pulse removes electrons.
• Reading: The charge presence or absence shifts the transistor's threshold voltage, detected as 0 or 1.

EEPROM Characteristics in NFC Chips

Memory Organization

• Type 2 tags (NTAG, Ultralight): 4-byte pages. NTAG 213 has 45 pages (144 bytes user memory).
• Type 4 tags (DESFire): Variable-length files within applications.
• Type 5 tags (ICODE): 4-byte blocks with different addressing.

EEPROM vs Other Memory in NFC

Write Endurance and Temperature

Applications updating frequently (counters, loyalty stamps) can approach the 100,000-cycle limit. A tag updated once per minute exhausts 100K cycles in ~70 days. For high-frequency writes, select chips with extended endurance or implement wear-leveling across memory blocks.

Temperature affects data retention: at 85 degrees Celsius, retention drops to 1-2 years. Automotive and outdoor applications should account for this when planning data refresh cycles.