mlx90111 ETC-unknow, mlx90111 Datasheet - Page 5

• Manufacturer Part Number: mlx90111
• Description: 128bit Read Write Transponder
• Manufacturer: ETC-unknow

General Description
The
transponder
capacitance and the external coil form a
resonant LC antenna that absorbs part of the
electromagnetic
transceiver LC antenna. Physically, a magnetic
coupling occurs between the transceiver, also
referred
antennas
To amplitude modulate (AM) the RF carrier, the
transponder damps the electromagnetic field by
switching a resistor in parallel with its coil. This
way the transponder repetitively transmits its
128bit-identification code (ID) to the transceiver,
which recovers the envelope of the damped
field, and decodes the ID.
The transceiver can send commands and data
to the transponder by modulating the amplitude
of the carrier.
POR level
When the transponder is placed in an external
radio
frequency and amplitude, the internal power
supply (VDD) can build up as charge on the
integrated buffer capacitance. The modulation
resistor is switched on and off as soon as VDD
has reached the Power On Reset (POR) level.
When the modulation resistor is switched on, the
LC circuit is no longer tuned, therefore no
energy is taken from the field, and VDD drops
due to internal consumption.
switching the modulation resistor on and off, it is
possible to oscillate around the POR level. This
phenomenon is referred to as hiccuping.
The modulation resistor is switched off when the
transponder drops below the POR level.
Sensitivity level
The minimum electromagnetic force (e.m.f.)
needed to avoid hiccuping is defined by
Vacsens. At this level the power supply will not
drop below the POR level while the modulation
resistance is switched on during modulation.
Clock recovery
The transponder takes its clock from the carrier
frequency. Depending on the speed option, the
carrier frequency is divided by 32(4kbaud),
64(2kbaud) to generate the bit rate.
MLX90111 128bit Read Write Transponder
MLX90111
frequency
to
as
IC.
energy
"reader",
is
(RF)
a
The
field
128bit
radiated
and
integrated
of
Read
transponder
Hence, by
appropriate
by
Write
tune
the
Page 5 of 12
2kbaud
4kbaud
Speed Total clocks
Demodulator
If the external RF field is AM modulated
according to the asynchronous control pattern
(ACP), the transponder stops transmitting the ID
and enters the Program Mode.
Data is then sent to the transponder using
Return to One encoding. First half bit is low (0)
or high (1), and the second half is high. In the
middle of each half bit one sample is taken. In
order for the transponder to detect the ACP
modulation a minimum modulation depth is
required.
more details on the write protocol.
RF limiter, or clamping
The build up of voltage on the resonant LC
circuit is limited to avoid damaging the internal
circuit.
Modulator
The modulator consists of a modulation resistor
that is switched in parallel with the resonant LC
circuit (antenna). Because in weak RF fields the
rising edge is much slower than the falling edge
of
modulator would give an asymmetrical envelope.
This is anticipated by delaying each falling edge
by a fixed number of RF clock pulses. The
modulator is hence driven asymmetrical. Each
ON state is reduced by 8 (4) clocks in 2 (4)
kBaud mode, and each OFF state is prolonged
by the same amount.
128bit Read Write Transponder
the
per Bit
64
32
envelope,
See timing specification below for
Clocks ‘ON’ state
Long ON = 32 – 4
Short ON = 16 – 4
Long ON = 64 - 8
Short ON = 32 - 8
MLX90111
a
symmetrically
Rev 1.12 5-Feb-01
Clocks ‘OFF’ state
Long ON = 64 + 8
Long ON = 32 + 4
Short ON = 32 + 8
Short ON = 16 + 4
driven