Tire Pressure Monitoring (TPM) System from Microchip

Tire Pressure Monitoring (TPM) System from Microchip

This document explains a typical tire pressure monitoring (TPM) system specifically intended for automotive use. It serves as a reference to design a real-world system based on various Microchip products. A TPM system primarily monitors the internal temperature and pressure of an automobile's tire. There is a variety of system approaches to follow; although this one is a rather comprehensive auto-location system.

An auto-location system can dynamically detect the position of a specific sensor, which is useful when tires are rotated. The heart of the TPM system is the Sensor/Transmitter (S/TX) device and it is based on Microchip's rfPIC12F675.

SYSTEM COMPONENTS
The TPM system consists of the following major component.
• Sensor/Transmitter Device
• RF Receiver Module
• Low Frequency (LF) Commander Device
• Control Unit
• Pressure Vessel (Tire)

Download Tire Pressure Monitoring System (TPMS) Application Note from Microchip

Infineon SP35 Tire Pressure Sensor

Infineon SP35 Tire Pressure Sensor


The SP35 is a highly integrated device which performs all necessary functions of a TPM module in the wheel for high-volume applications. The device contains the sensing element, the micro controller, the LF receiver and the transmitter in one package.

The Sensor design is based upon Infineon’s patented bulk micro-machined sensing technology which allows highly reliable measurements in harsh environments. The SP35 measures pressure, temperature, supply voltage and radial acceleration. The device is offered with a pressure range of 100–450 kPa.

The Infineon SP35 Tire Pressure Sensor incorporates all the major active functions of wheel-mounted TPMS in a single package. The integrated device, mounted on a printed circuit board with a battery and antenna, enables tier-one suppliers to meet the requirements of the new regulations. Its single package integrates an MEMS pressure sensor, acceleration sensor and temperature sensor with an 8-bit controller and wireless communication module. It eliminates the need for separate communication chips, thus reducing complexity and reportedly cutting costs by about 10 percent.

Major Functional Blocks of SP35 Tyre Pressure Sensor

Pressure sensor
Radial acceleration sensor
Temperature sensor
Battery voltage sensor
8051 compatible microcontroller
6 kByte onchip FLASH memory
256 byte RAM
Advanced power control/wake-up system to minimize battery consumption
RF transmitter for 315 and 434 MHz
Selectable output power 5 or 8 dBm
LF receiver for 125 kHz
P-DSOSP-14-6 Package
Download Infineon SP35 Tire Pressure Sensor Application Note

About Thermistor

Normally most of the electronic components like capacitors, bridge rectifiers, transistors, IC, diodes, resistors and etc have their own code which is quite easy to read. For example, a 104 capacitor we know that it is a .1 microfarad capacitor, a 1n4007 have the spec of 1000 volt with 1 ampere and so forth. However, for the Thermistor there are so many part numbers and almost all of them have different code which make us as electronic repairer have a hard time trying to locate the part. Usually what i did was to get a replacement from a junk board and i have plenty of junk boards!
I wish that those Thermistor manufacturers could set a standard code so that it would make our life easier especially for those who are new in this repair field. Beginners might have thought of the component could be a Varistor and a wrong replacement might cause the equipment not to function. For your information, if you did not look at the board location you would think that a Varistor is a Thermistor and a Thermistor is a Varistor

Sensor Technology Handbook

Sensor Technology Handbook

Sensor Projects

Sensor Projects

Temperature Sensor Handbook

Temperature Sensor Handbook

Sensor Technology Handbook

Sensor Technology Handbook

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