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E5551

Standard R/W Identification IC with Anticollision

Temic Semiconductors 

e5551

Operating the e5551

General

The basic functions of the e5551 are: supply IC from the

coil, read data from the EEPROM to the reader, write

data into the IC and program these data into the

EEPROM. Several errors can be detected to protect the

memory from being written with the wrong data (see

figure 21).

Supply

The e5551 is supplied via a tuned LC circuit which is con-

nected to the Coil 1 and Coil 2 pads. The incoming RF

(actually a magnetic field) induces a current into the coil.

The on-chip rectifier generates the dc supply voltage

(VDD, VSS pads). Overvoltage protection prevents the IC

from damage due to high-field strengths. Depending on

the coil, the open-circuit voltage across the LC circuit can

reach more than 100 V. The first occurrence of RF trig-

gers a power-on reset pulse, ensuring a defined start-up

state.

Read

Reading is the default mode after power-on reset. It is

done by switching a load between the coil pads on and off.

This changes the current through the IC coil, which can

be detected from the reader unit.

Start-Up

The many different modes of the e5551 are activated after

the first readout of block 0. The modulation is off while

block 0 is read. After this set-up time of 256 field clock

periods, modulation with the selected mode starts.

Any field gap during this initialization will restart the

complete sequence.

Read Datastream

The first block transmitted is block 1. When the last block

is reached, reading restarts with block 1. Block 0, which

contains mode data, is normally never transmitted. How-

ever, the mode register is continuously refreshed with the

contents of EEPROM block 0.

Reader coil

IAC

125 kHz

Energy

Tuned LC

e5551

Data

Figure 8. Application circuit

Damping on

Damping off

VCoil 1 – Coil 2

v2 ms

Power-on

reset

Loading block 0 (256 FC[2 ms)

* FC –> Field clocks

Read data with configured

modulation and bitrate

Figure 9. Voltage at Coil1/Coil2 after power-on

6 (21)

Rev. A2, 19-Apr-00

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