The TK4100​ is a low-frequency (LF) 125 kHz read-only RFID chip, widely used as a low-cost alternative to the EM4100/EM4200 family. It is primarily designed for simple identification tasks in access control and asset tracking.

1. Core Definition

The TK4100 is a CMOS integrated circuit​ for passive RFID transponders. It is a factory-laser-programmed, read-only​ device, meaning its 64-bit unique ID (UID)​ is permanently burned into the chip during manufacturing and cannot be altered​ in the field. It is fully protocol-compatible with EM4100/EM4200​ chips.

2. Key Technical Specifications

The chip requires only an external antenna coil to function, as all necessary tuning and power management components are integrated.

3. Data Format

The 64-bit data frame follows the standard EM format:

• 9 Header Bits​ (all '1's)
• 40 Data Bits​ (8-bit manufacturer code + 32-bit unique serial number)
• 14 Parity Bits​ (Error checking)
• 1 Stop Bit​ (0)

This structure ensures direct compatibility with existing EM4100 readers.

4. Common Applications

• Access Control & Attendance: Office doors, gate entry (CR80 cards, key fobs).
• Asset Tagging: Industrial process control, logistics tracking.
• Animal Identification: Low-cost livestock tags.
• Simple ID Systems: Where a unique, unchangeable number is sufficient.

5. Comparison with T5577 & EM4200

In summary, the TK4100 is a cost-effective, disposable​ RFID solution for applications that require a simple, permanent ID number without the need for data rewriting.