EM4450

EM4550

Copyright

 2003, EM Microelectronic-Marin SA

10

www.emmicroelectronic.com

Power-On-Reset (POR)

When the EM4450/4550 with its attached coil enters an electromagnetic field, the built in AC/DC converter will supply the

chip. The DC voltage is monitored and a Reset signal is generated to initialise the logic. The contents of the Control word

and Protection word will be downloaded to enable the functions (INIT). The Power-On-Reset is also provided in order to

make sure that the chip will start issuing correct data. Hysteresis is provided to avoid improper operation at the limit level.

Fig. 17

Lock All / Lock Memory Area

The EM4450/4550 can be converted to a Read Only chip or be configured to Read/Write and Read Only Areas by

programming the protection word. This configuration can be locked by write inhibiting the Write Protection Word. Great care

should be taken in doing this operation as there is no further possibility to change the Write Protection Word. The Control

Word can also be protected in the same way thus freezing the operation mode.

Clock Extractor

The Clock extractor will generate a system clock with a frequency corresponding to the frequency of the RF field. The

system clock is used by a sequencer to generate all internal timings.

Data Extractor

The transceiver generated field will be amplitude modulated to transmit data to the EM4450/4550. The Data extractor

demodulates the incoming signal to generate logic levels, and decodes the incoming data.

Modulator

The Data Modulator is driven by the serial data output from the memory which is Manchester encoded. The modulator will

draw a large current from both coil terminals, thus amplitude modulating the RF field according to the memory data.

AC/DC Converter and Voltage Limiter

The AC/DC converter is fully integrated on chip and will extract the power from the incident RF field. The internal DC

voltage will be clamped to avoid high internal DC voltage in strong RF fields.

Special Timings

EM4450/4550 is executing internal operations. During these pauses, the RF field will be influenced.

Fig. 18

t

V

DD

t

Reset

V

prh

V

prhys

t

init

EM4450 Active

During Twa and Twee, the signal on the coil is

damped due to a higher current consumption.

32 32

RF periods :

t

pp

Same modulation

as for a normal bit

16 16

(Opt64)

(Opt32)

64

32

(Opt64)

(Opt32)

t

wa

3200

2624

(Opt64)

(Opt32)

t

wee