Tpms

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Freescale Single-Package Tire Pressure Monitoring System (TPMS)

Contents
Overview .............................................................................................................................................................3 Safety Considerations.........................................................................................................................................3 Economic Considerations ...................................................................................................................................4 Direct and Indirect Tire Pressure Monitoring System (TPMS) ...........................................................................5 The Freescale Direct Tire Pressure Monitoring System (TPMS).........................................................................6 Conclusion ..........................................................................................................................................................7

Tire Pressure Monitoring System



Freescale Semiconductor, Inc.

Overview
Many people seem to think that maintaining proper tire pressure is a nuisance and keeping ourcars clean deserves more attention. In fact, a Rubber Manufacturers Association survey discovered that nearly 70 percent of American drivers wash their vehicles at least once a month while only 15 percent check their tire inflation that frequently. Unfortunately, driving on improperly inflated tires can be deadly. The National Highway Traffic Safety Administration (NHTSA) estimates that 3,000accidents and 535 fatalities per year involve flat tires or blowouts, both of which can be the result of improperly inflated tires. But improperly inflated tires is a global safety issue. In France, the Sécurité Routière estimates that nine percent of all fatal road accidents are the result of under-inflated tires. The German DEKRA found that tire problems are linked to an estimated 41 percent of allinjury accidents. Its recent study in Germany found that 75 percent of vehicles on the road had at least one tire under-inflated by three pounds-per-square-inch (psi) or more. Under-inflated tires can also impose an economic hardship on the owner, particularly in businesses that heavily rely on road transportation. The economic impact can be especially serious in the commercial trucking industry.Just a few pounds of under-inflation can cost trucking firms thousands of dollars per year in heightened fuel costs and increased retread and tire replacement expenses.

Safety Considerations
Properly inflated tires reduce blowouts and braking distances, mitigate hydroplaning on wet surfaces and improve overall vehicle handling. Proper inflation also increases the tire life and improves fuelefficiency, lowering the cost of vehicle operation. These benefits are frequently forfeited by motorists who fail to monitor their tire pressures to maintain the proper inflation levels. Under-inflation reduces tire stiffness, which degrades cornering forces and can result in skidding or loss of control in tight cornering or quick lane-changing maneuvers. Under-inflated tires also increase stoppingdistances because each tire’s footprint and the pressure it exerts on the road has been altered. Combining under-inflation with high-speed and/or overloaded conditions can also result in tire blowouts, a catastrophic event that can cause the vehicle to veer into oncoming traffic or spin out of control. Even if control of the vehicle is maintained in such cases, changing a tire on the roadway oftenexposes the motorist to the dangers of onrushing traffic, particularly at night or in adverse weather conditions. Whereas over-inflated tires are generally not considered to be as dangerous as under-inflated tires, they can still jeopardize the safety of vehicle occupants and increase the chances of tire failure. An over-inflated tire is stiffer with a smaller footprint in contact with the...