R

EM4100

Block Diagram

CLOCK

EXTRACTOR

FULL WAVE

RECTIFIER

DATA

MODULATOR

SEQUENCER

DATA

ENCODER

MEMORY

ARRAY

Logic

Clock

Serial

Data Out

Modulation

Control

Cres

COIL1

COIL2

AC1

AC2

+

-

Csup

VDD

VSS

a

a: open only for PSK version

Fig. 5

Functional Description

General

The EM4100 is supplied by means of an electromagnetic

field induced on the attached coil. The AC voltage is

rectified in order to provide a DC internal supply voltage.

When the last bit is sent, the chip will continue with the first

bit until the power goes off.

Full Wave Rectifier

The AC input induced in the external coil by an incident

magnetic field is rectified by a Graetz bridge. The bridge

will limit the internal DC voltage to avoid malfunction in

strong fields.

Clock Extractor

One of the coil terminals (COIL1) is used to generate the

master clock for the logic function. The output of the clock

extractor drives a sequencer.

Sequencer

The sequencer provides all necessary signals to address

the memory array and to encode the serial data out.

Three mask programmed encoding versions of logic are

available. These three encoding types are Manchester,

biphase and PSK. The bit rate for the first and the second

type can be 64 or 32 periods of the field frequency. For the

PSK version, the bit rate is 16.

The sequencer receives its clock from the COIL1 clock

extractor and generates every internal signal controlling the

memory and the data encoder logic.

Data Modulator

The data modulator is controlled by the signal Modulation

Control in order to induce a high current in the coil. In the

PSK version, only COIL2 transistor drives this high current.

In the other versions, both coil1 and coil2 transistors drive it

to Vdd. This will affect the magnetic field according to the

data stored in the memory array.

Resonance Capacitor

This capacitor can be trimmed in factory by 0.5pf steps to

achieve the absolute value of 74pf typically. This option,

which is on request, allows a smaller capacitor tolerance on

the whole of the production.

Copyright © 2004, EM Microelectronic-Marin SA

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