Bullet Sensors & Transducers e-Digest, Vol. 66, Issue 4, April 2006: Product News

    (ISSN 1726- 5479)


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Interlock-Switch Sensor Interface IC


Melexis presents its MLX16305 interlock-switch sensor interface IC. The MLX16305 allows fail safe monitoring of current modulated sensors, typically remote interlock switches with diagnostics requirements.


Interlock switches currently are in use at high volume both in Europe and in the US with resistive as well as 2-wire Hall effect switches for seat belt buckle presence detection. Other typically automotive applications include presence detection of airbags, and monitoring of door, hood and trunk latches and locks. The MLX16305 is ideal also for industrial applications with safety interlock switches, like security doors in machinery, tools or appliances. This IC may also be used to interface with 2-wire analog sensors in general, for instance in combination with the MLX90308/90314 sensor interface ICs in current mode.


The MLX16305 is a regulated supply with short circuit protection for 12V battery applications, with output current and output voltage sensing capability. The device is produced in a HV-CMOS technology and qualified for 40 V load dump protection. Its high output current range (up to 40 mA) guarantees adequate "cleaning current" for (resistive) contact switches. The high measurement accuracy allows the tracking of any possible contact aging, and therefore it allows predicting imminent contact failures. The wide output voltage range allows it to be applied with most viable 2-wire hall sensors. It even allows the use of general purpose 3-wire Hall Effect switches like the US5782 in a 2-wire scheme.


The MLX16305 makes it simple to distinguish the actual open or close state of a remote switch from possible failure conditions like open or broken wires, short circuits to battery or to ground or even shorts between wires. In a six switch application the microcontroller can diagnose 20 conditions one by one by interpreting the analog voltage output from the MLX16305.


The monitoring capability of the controller can be further extended to 12 (18, ...) switches using one (two, .) additional digital output(s) on the microcontroller. This digital output can set the analog output of an MLX16305 to high impedant, allowing to multiplex several MLX16305 devices on the same IO's of the controller.


Henri Vanderhenst, Business Unit Manager, comments:  "There is no safety switch monitoring product on the market that allows such extensive diagnostics as the MLX16305. Furthermore its' flexibility and accuracy allow it to be used by any type of two-wire current sensor application. The MLX16305 is a typical example of a successful automotive Application Specific Standard Product (ASSP) that can be leveraged by the industrial market as well."

MLX16305 interlock-switch sensor interface IC




Mr. Tanguy Scorpati
Transportstraat 1, 3980 Tessenderlo
Tel.: +32 (0) 12 67 20 02, fax: +32 (0) 12 67 20 03
E-mail: tas@melexis.com



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