EM4069
EM4169
Functional Description
The IC builds its power supply through an integrated
rectifier. When it is placed in a magnetic field the DC
internal voltage starts to increase.
As long the power supply is lower than the power on reset
(POR) threshold, the circuit is in reset mode to prevent
unreliable operation. In this mode the modulator switch is
off.
After the supply voltage cross the POR threshold, the
circuit goes in read mode and transmits periodically the
128 data bits from EEPROM.
The power on reset is designed with a typically 250mV
hysteresis. The specified value in the DC electrical
characteristic table indicates the high level-switching
threshold. Ones the supply voltage had reached this level,
the device work in read mode and reenter in reset mode if
the supply voltage decrease under the lower threshold
(~V
POR
– 250mV).
In read mode the IC transmits periodically either the 128
data bits from EEPROM or 64 data bits from ROM if
command 2 has been sent. The bits are Manchester or BI-
phase coded and issued by switching the modulator load in
parallel to the coil ON and OFF. The read out process is
repeated continuously without any pause as long as power
level is greater than the POR threshold low.
While the IC is operating in read mode it checks the coil
signal once every bit period. If it detects a certain reader
induced amplitude modulation of magnetic field it stops
modulating and waits for a command word. In the case the
EEPROM write command is detected the contents of
selected EEPROM word is modified. Read ROM command
will change the output sequence to the data provided by
the laser ROM continuously.
The Reset command returns to the initial mode as after a
Power on Reset.
VDD
VPOR
Hysteresis
t
Reset
P4069 Active
EM4069 Active
t
Fig. 4
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 EM4069. 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 transceiver. The modulator will draw a large current
from both coil terminals, thus amplitude modulating the RF
field according to the selected memory data.
Block description
Power On Reset (POR)
When the EM4069 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 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.
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 voltage in strong
RF fields.
Lock All / Lock Memory Area
The EM4069 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 writing operation.
Copyright
2003, EM Microelectronic-Marin SA
4
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EMMICRO [ EM MICROELECTRONIC - MARIN SA ]
