2

4709F–RFID–06/06

TK5551

Figure 1-1.

System Block Diagram

2.

General

The transponder is the mobile part of the closed coupled identification system (see Figure 1-1),

whereas the read/write base station is based on the U2270B or on discrete solutions, and the

read/write transponder is based on the IDIC e5551.

The transponder is a plastic cube device consisting of the following parts:

• The transponder antenna, realized as a tuned LC circuit

• Read/write IDIC (e5551) with EEPROM

3.

Transponder Antenna

The antenna consists of a coil and a capacitor for tuning the circuit to the nominal carrier fre-

quency of 125 kHz. The coil has a ferrite core for improving the distance of read, write and

programming operations.

4.

Read/Write IDIC e5551

The read/write IDIC e5551 is part of the transponder TK5551. The data are transmitted bi-direc-

tionally between the base station and the transponder. The transponder receives power via a

single coil from the RF signal generated by the base station. The single coil is connected to the

chip and also serves as the IC’s bi-directional communication interface.

Data are transmitted by modulating the amplitude of the RF signal. Reading of register contents

occurs by damping the coil by an internal load. Writing into registers occurs by interrupting the

RF field in a specific way. The TK5551 transponder operates at a nominal frequency of 125 kHz.

There are different bit rates and encoding schemes.

The on-chip 264-bit EEPROM (8 block, 33 bits each) can be read and written block wise from

the base station. The blocks can be protected against overwriting by using lock bits. One block is

reserved for setting the operation modes of the IC. Another block contains a password to pre-

vent unauthorized writing.

See e5551 data sheet for more detailed information of the IDIC.

e5551

RF Field

Data

Power

Coil

C

(e5551 + coil + C in plastic package)

TK5551 Transponder

Base Station

U2270B read/ write IC

MARC4 series

microcontroller