R
EM4150
EM4350
AC/DC Converter and Voltage Limiter
Power On Reset (POR)
When the EM4150 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.
VDD
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.
Resonance Capacitor
The Resonance Capacitor is integrated, and its tolerance
is adjusted to ± 2% over the whole production.
Typical Capacitor Variation
versus Temperature
V
prh
V
prhys
Cr Tolerance [%]
100.3
100.2
t
Reset
100.1
t
init
EM4150 Active
100.0
99.9
99.8
t
99.7
-50
-30
-10
10
30
50
70
90
Fig. 18
Temperature [°C]
Fig. 19
Lock All / Lock Memory Area
The EM4150 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.
Special Timings
The Processing Pause Time (tpp), Write Access Time
(twa) and EEPROM Write Time (Twee) are timings
where the EM4150 is executing internal operations.
During these pauses, the RF field will be influenced.
RF periods : 32 32 (Opt64)
16 16 (Opt32)
64
32
(Opt64)
(Opt32)
3200
2624
(Opt64)
(Opt32)
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.
t
pp
Same modulation
as for a normal bit
During Twa and Twee, the signal on the coil is
damped due to a higher current consumption.
t
wa
t
wee
Fig. 20
Data Extractor
The transceiver generated field will be amplitude
modulated to transmit data to the EM4150. 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.
Copyright
©
2004, EM Microelectronic-Marin SA
9
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EMMICRO [ EM MICROELECTRONIC - MARIN SA ]
