MLX74190
Two-Fold High Power LF Initiator
With integrated Immobilizer
390107419001 Page 1 of 14 Sept-2014
Rev. 001 Product Preview
Features and Benefits
2 High power independent drivers (2.5Apeak in
square and 1Apeak in sine mode)
Full bridge drive capabilities
Built-in protection features (antenna fault detection,
over current and T°) for guaranteed safe operation
in all conditions
Easy-to-use through SPI interface
Built-in ASK and FSK immobilizers
Application Examples
Passive Start system
TPMS Initiator
LF door opener
Active RFID initiator
Ordering Information
PF (Lead free TQFP 7x7 48 leads)
This document is a Product Preview, to get access to the full datasheet and related documentations, please directly
contact Melexis at sales_europe@melexis.com or sales_usa@melexis.com.
Description
The MLX74190 low-frequency (LF) initiator IC consists in two high power LF drivers and built-in immobilizers
(IMMO).
The main application for the MLX74190 is automotive remote
passive start, where the IC transmits a high power LF telegram to
wake-up the key inside the car. The key sends out its identification
number to the car via an ultra-high frequency (UHF) signal,
enabling the engine to start. The MLX74190 also features two built-
in Immobilizers (for ASK and FSK communications), used when the
battery of the key is depleted. In this case, the key is placed in a
specific zone close to the initiator and a full passive RFID
communication is initiated. The load modulation signal returns by
the key is received and demodulated by the MLX74190.
The MLX74190 can also serve for a similar purpose with other vehicles such as; motorcycles, scooters, all-
terrain vehicle (ATV), jet skis, snowmobiles and motorboats, where the key holder can be detected when
approaching the engine and will be able to activate it from a “Start” button, or as a ‘dead man switch’ so that if
the driver falls off then the engine is automatically cut. In addition it may be incorporated into building access
systems, tire pressure monitoring system (TPMS) initiators and pet identification system.
Both LF drivers are independently programmable to generate sine (max. 1Ap) or square (max. 2.5Ap) waves,
with a frequency from 109kHz to 140kHz and an output amplitude from 0.25 to 32Vpp. The two drivers can
be used in full or half bridge configuration and are protected against overload (over-current and over-
temperature). A built-in diagnosis function allows detecting any wrong connection with the LF antenna (Short
to GND, Short to Vbat, open load or wrong resonance frequency).
The MLX74190 is supplied by an external VS voltage from 6-40V and VDD voltage of typically 5V. The VS
voltage can be generated by an external DC-DC converter or by DC voltage from vehicle supply.
The MLX74190 is controlled through a standard SPI interface (SDI, SDO, SCK and NCS) and an interrupt pin
is generated on-purpose by the IC. The MLX74190 is clocked either with a 2 MHz clock frequency signal
coming from the MCU or by an on-chip oscillator connected to an external 4 MHz crystal or ceramic
resonator.
Figure 1: Passive Start Application
