MLX90110 Datasheet, PDF (4/10 Pages) List of Unclassifed Manufacturers – 128bit OTP/RW Transponder

MLX90110
128bit OTP/RW Transponder
General Description
The MLX90110 is a 128bit Read Write
transponder IC for fixed distance writing. The
integrated tune capacitance and the external coil
form a resonant LC antenna that absorbs part of
the electromagnetic energy radiated by the
transceiver LC antenna. Physically, a magnetic
coupling occurs between the transceiver, also
referred to as "reader", and transponder
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 (RF) field of appropriate
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. Hence, by 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.
Demodulator
If the external RF field is AM modulated
according to the asynchronous control pattern
(ACP, see below), the transponder stops
transmitting the 128bit ID and enters the
Program Mode. Each bit period a sample is
taken. The transponder synchronizes on the first
bit (startbit) of each new word that is transmitted.
The high and low programmation levels (Vacpr)
have to be applied in order for the transponder to
detect the ACP and recover the data, which are
sent to tag during a programmation cycle.
For this reason the transponder can only be
programmed at a certain distance which is
defined by the system parameters, taken Vacpr
into account.
RF limiter, or clamping
The build up of voltage on the resonant LC
circuit is limited to avoid damaging the internal
circuit. This causes the transponder Q to drop at
higher fields.
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 the envelope, a symmetrically driven
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.
Speed Total clocks
per Bit
2kbaud
64
4kbaud
32
Clocks ‘ON’ state
Long ON = 64 - 8
Short ON = 32 - 8
Long ON = 32 – 4
Short ON = 16 – 4
Clocks ‘OFF’ state
Long ON = 64 + 8
Short ON = 32 + 8
Long ON = 32 + 4
Short ON = 16 + 4
MLX90110 128bit MTP Transponder
Page 4 of 10
Rev 1.14 1-Dec-2000