MLX74190 Datasheet, PDF (9/14 Pages) Melexis Microelectronic Systems – Two-Fold High Power LF Initiator With integrated Immobilizer

MLX74190
Two-Fold High Power LF Initiator
With integrated Immobilizer
4.8 Immobilizer FSK
The FSK demodulation block is intended to detect and demodulate the response of the transponder
compliant with FSK modulation (frequency shift keying). The demodulated data are accessible by the MCU
through the D_OUT output pin. The FSK signal is a modulated frequency signal, where high and low bits are
coded with two different frequencies.
The FSK_RXi inputs are connected to the LF antenna through external resistors Rin and Rfb, which must be
adjusted according to the voltage swing on the external antenna.
4.9 Digital SPI Interface
The MLX74190 is interfaced and configured through a standard Serial Peripheral Interface bus (SPI). The
communication is full duplex, the host MCU always acts as a Master and the MLX74190 always acts as a
slave.
 NCS: Non Chip Select
 SCLK: Serial Clock
 SDI: Serial Data In
 SDO Serial Data Out
4.10 SPI Commands
The MLX74190 is controlled through a set of SPI commands sent by the host MCU. These SPI commands
are used to configure the internal registers of the MLX74190.
4.11 Failure Flags
The following failures / warnings are detected by the MLX74190:
 VS/VDD under voltage
 Temperature monitoring (pre-warning & over temperature)
 Antenna over current
 SPI-errors
4.12 Antenna diagnosis
The Diagnosis block is designed to detect any failure related to the antenna connected on the LF driver
outputs.
Following potential antenna failures are diagnosed:
 Antenna short circuited to VS/GND
 Disconnected antenna or incorrect Self resonance frequency
4.13 Current Measurement
The current measurement block allows monitoring on time the AC current flowing through the selected Output
Antenna Driver. The analog voltage corresponding to the measured current is available on the pin
IP_SENSE.
390107419001
Rev. 001
Page 9 of 14
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Sept-2014