EEPROM

What Is EEPROM?

EEPROM (Electrically Erasable Programmable Read-Only Memory) is the non-volatile memory technology used in virtually all NFC tag 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.