Analysis of Vehicle TPMS Sensor Technology
TPMS is the abbreviation of “TIrePressureMonitoringSystem†for automobile tire pressure monitoring system. It is mainly used for automatic monitoring of tire air pressure in real time when the car is running, and alarming for tire leakage and low air pressure to ensure driving safety. It is a driver and passenger. The car's life safety guarantee system.
The tire pressure monitoring module of TPMS consists of five parts:
(1) a smart sensor SoC with a combination of pressure, temperature, acceleration, voltage detection and post-signal processing ASIC chips;
(2) 4-8 bit microcontroller (MCU);
(3) RF radio frequency transmitting chip;
(4) lithium sub-battery;
(5) Antenna.
See Figure 1, Figure 2 is a physical map of the finished product. The shell is made of high-strength ABS plastic. All devices and materials must meet the automotive temperature range of -40 ° C to +125 ° C.
Figure 2 Physical map of the finished tire pressure monitoring module of TPMS
The smart sensor is a pressure sensor integrated with silicon micromachining (MEMS) technology, an accelerometer chip and a temperature sensor, battery voltage detection, internal clock and analog-to-digital converter (ADC), sampling/holding (S/H) ), SPI port, sensor data calibration, data management, ID code and other functions of digital signal processing ASIC chip. With mask programmability, it can be configured with customer-specific software. It is made up of several chips from MEMS sensors and ASIC circuits, which are fabricated in a package using an integrated circuit process (Figure 3). A pressure/temperature inlet (Figure 4) is placed over the package to introduce pressure directly into the stress film of the pressure sensor (Figure 5), which also directs the ambient temperature directly to the semiconductor temperature sensor.
The MEMS silicon piezoresistive pressure sensor adopts a circular fixed stress silicon film inner wall around the periphery, and uses MEMS technology to directly inscribe four high-precision semiconductor strain gauges at the maximum surface stress, forming a Wheatstone measuring bridge as a power Transforming the measuring circuit, the physical quantity of pressure is directly converted into electric quantity, and the measuring precision can reach 0.01-0.03% FS. The structure of the silicon piezoresistive pressure sensor is shown in Fig. 5. The upper and lower layers are glass bodies, and the middle is a silicon wafer. The upper part of the stress silicon film has a vacuum chamber, making it a typical absolute pressure sensor.
To facilitate identification of the TPMS receiver, each pressure sensor has a unique 32-bit ID code that produces 400 million unique numbers.
Figure 3 Pressure, acceleration and ASIC/MCU combination packaged in one package
Figure 4 pressure / temperature inlet hole
Figure 5 Silicon piezoresistive pressure sensor structure
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