MLX90132 Datasheet, PDF (4/44 Pages) Melexis Microelectronic Systems – 13.56MHz RFID / NFC Transceiver

MLX90132
13.56MHz RFID / NFC Transceiver
2 General Description
MLX90132
Rx Reader
RX1
RX2
Tag
Front-End
TX1
Tx Drivers
TX2
GND_TX GND_RX GND_dig
VDD_TX VDD
XIN
XOUT
Power Supply
Clock
Status & Control
register
Digital
demodulation
Tag/Field
detector
Digital Modulation
Digital
control
&
protocol
handling
Interface
block
NSS
SCK
MISO
MOSI
IRQ_IN (UART_RX)
IRQ_OUT (UART_TX)
Figure 2: MLX90132 simplified block diagram
Power Supply
The MLX90132 is supplied with the 2 pins V_DD (supply of the digital and analog blocks) and V_{DD_TX} (direct
supply of the TX Drivers), each requiring a nominal stable external power supply from 2.7 to 5.5 volt. Both
pins V_DD and V_{DD_TX} are independent and could be connected together to the same power supply level or to
different ones. The current drain depends on the antenna impedance and on the output matching network
configuration.
Special attention should be paid to the filtering of V_{DD_TX}. Typically, a ferrite and a decoupling capacitor will be
added close to the MLX90132 device.
TX Drivers
The transmission stage of the MLX90132 is composed of two differential outputs T_X1 and T_X2, providing
square waves with a frequency of f_HFO (typ. 13.56MHz), an amplitude of V_{DD_TX} and with a phase shift of 180
degrees. Each output is featuring an equivalent serial resistance R_ON which has to be taken into account
when calculating the antenna matching network.
The transmission stage of the MLX90132 could be modulated using Amplitude Shift Keying (ASK) with a
modulation index between 10% and 100%. The modulation index is automatically set with the selection of the
protocol of communication, using the command Protocol select command (0x02). The modulation index could
be fine adjusted by following the procedure described in the section Modifying internal settings for optimal
performances.
In TAG emulation mode, the two outputs TX1 and TX2 are internally connected together, insuring a proper
parallel resonance of the antenna. In this configuration, the two serial capacitors CS are put in parallel to the
parallel capacitor CP. This operation is done automatically when selecting TAG emulation modes and should
also be taken into account when defining an EMI filter for EMC considerations.
3901090132
Rev. 009
Page 4 of 44
Jan-2014