Set net news, various semiconductor recently acquired Fairchild semiconductor, 50 years of experience in automobile industry for the customer, is the world's second largest non microcontroller car semiconductor suppliers, including for automatic driving and function of auto electronic comprehensive solutions. In the process of car fast moving towards intelligent and sensor is particularly critical. Under this trend, various semiconductor launched the world's first passive, no additional single-chip microcomputer control of intelligent sensor, based on the RFID protocols, single chip transceiver integrated energy function, and can detect temperature, humidity, pressure and distance, create a new pattern of sensor applications.

The function of the intelligent passive sensor module and working principle

Intelligent passive sensor consists of three functional modules: antenna module, sensor module based on Magnus IC, power supply, SCM, processing module, as shown in figure 1. Antenna module based on UHF wireless communication industry standard second edition protocols, and collect the energy for the use of internal processing unit. Power supply, SCM, processing module compatible with RFID ecological system components, available standard of RFID reader read, etc. Based on Magus IC (the first passive RFID sensor chip) sensor module, can adjust the front end of the automatic tuning module can be perceived by the internal circuit impedance change detection environment condition, such as humidity and pressure, every intelligent sensor has an independent information, to read the temperature chip detection distance by wireless signal strength/sport/state, every intelligent sensor internal memory holds a unique ID for identification. The final accuracy depends on the UHF RFID working frequency range of the sampling frequency.

Semiconductor manufacturing initiative intelligent passive sensor power for the development of smart car 0 intelligent passive sensor based on RFID protocols, transmission frequency range of 860 to 960 MHz. First, send the RFID reader reads commands, recharge RFID sensor at the same time, as the RFID chip is to start working after charging, read related sensor information, and through the feedback to the RFID reader antenna.

The advantage of intelligent passive sensor

Compared with the existing sensor, smart sensor has many advantages: the existing sensor should be placed on each PCB detection sensors, power, control and communication chip and MCU, and volume size, cost is high, the need to maintain; Each node and intelligent passive sensor find smart tags for passive power, single-chip computer and data processing on the independent reader, no batteries, size small, thin, like a tape every reader can support multiple tags, and low cost, no maintenance.

Although auxiliary UHF RFID electronic tag is also a passive tag, node without batteries, through dar implementation code (EPC) code and RFID unique ID, but was working adsorption material surface reflection can reduce the effective reading distance, and no sensor function; No intelligent passive sensors work adsorption materials surface reflection, effective reading distance, so as to upgrade and integration of humidity, pressure, distance and temperature detection sensor and other functions.

Intelligent passive sensor applications

An intelligent passive sensor reader can read thousands of sensing information, so only need a reader in the car with multiple antenna can meet the demand of many sensors, such as liquid level detection, tire pressure monitoring (TPMS), temperature detection, chairs, wiper, indoor air and headlamps humidity/leakage detection, etc.

1. Detection of the seat

The seat was detected by sensors to achieve system to protect the safety of passengers. Commonly used judgment seat detection system based on weight or pressure, any object like a bag of groceries, will trigger a seatbelt warning, misjudgment rate is quite high.

Various semiconductor passive sensor scheme, the new intelligent wireless sensor tags embedded in seat (humidity sensor tags embedded in back of the chair, pressure sensor tags embedded in the seat cushion). Humidity label through the human body detection element whether anyone can determine the seat, eliminating items trigger a seatbelt warning trouble, improve reliability. Pressure tag weight tests determine the size of the passengers, and crew sitting position can be feedback to intelligent airbag control unit to optimize the airbag release Angle to enhance security. The scheme can check-out car seats remaining in the body and can be extended to the rear seat and the testing of child safety seats, and multiple seat share a control unit (reader) to control, embedded passive humidity sensor without any connectors and wiring harness.

2. The liquid level detection

Auto liquid level test include the fuel tank of oil, engine oil, brake fluid level and acidic liquid level detection of liquid level etc. Currently on the market of auto liquid level detection system needs to connect wires into the sink. And various semiconductor intelligent passive sensors can be left in the sink without any fuses and electrical problem: using fluid of dielectric constant liquid level detection and can detect a variety of liquid, including water, gas, gasoline, oil, solvent, acid, etc., joint type of humidity sensors placed in the outside of the tank, the sensor tags, the longest do not exceed 4 inches long distance measure can use multiple tags, by detecting connected pipes can realize accurate measurement, two sensors installed on the top and bottom respectively, through the change of dielectric constant testing (such as gas mixture).

3. The rain sensor - automatic wiper start control

Currently used car wiper control system based on sunshine refraction, are susceptible to interference and trigger false action. And innovative intelligent passive sensor using the humidity test, covering the windshield wider area, can be multiple different location of the humidity sensor tag on the windshield, detect the windshield high dielectric constant of water, the windshield sensor can be determined by calibration, the number of light sensor can detect different sensors. The next generation product antenna can be embedded into the glass for installation, use the electrical impedance change engine detected between the two feet, realize only one sensor intelligent control of windscreen wiper.

4. The area of wireless temperature monitoring

When used in wireless temperature monitoring of the region, the existing temperature sensors are lead, active, and the installation location restricted. Innovative intelligent passive sensors can be used for multiple areas of wireless temperature monitoring, the only RFID identification number support automatic identification, reader and interior gateway are linked together, the automatic air conditioning system can automatically read data in real time and high precision control, built-in to 40 ℃ to + 85 ℃ (+ / - 1 ℃) precision measuring range, the next generation of products will support temperature above 125 ℃.

5. Tire pressure monitoring system

Tire pressure monitoring system used for real-time automatic monitoring tire pressure in the process of driving, in the event of a tire pressure alarm in time when the danger signs of inadequate or excessive, improve driving safety and fuel economy, prolong the life time of the tyre, reduce the wear and tear of the suspension system. Currently on the market for tire pressure monitoring system of chip sensor is installed in each round circle and stem, battery power supply, power consumption is higher than 250 uW, accelerometers are needed to avoid tire, when not mobile battery runs out, need to be reprogrammed to locate during tire rotation, cost is higher than $30.

And various semiconductor intelligent passive sensor is single chip solution, no need for batteries and acceleration sensor, a single sensor module power consumption is lower than 15 uW, so no matter when tire rotation was still detectable tire pressure and temperature information. Intelligent passive sensor tag on each tire, the only RFID identification number to support automatic tyre localization, software without reprogramming.

6. Auto logoff leakage detection

Depot in front of the car factory will be on the high pressure water immersion test, close the car doors and Windows, high pressure water jet was carried out on the car, from different angles to test the car's sealing performance and chassis is weeping. Currently on the market of the scheme with the method of artificial detection, more time-consuming and error-prone, once detected leakage, must to remove to the car chassis for repair.

Various semiconductor intelligent passive sensors used in such applications, a typical configuration includes six to ten more sensors, each position assigned only EPC, according to the specific needs of vehicle size and oems, placed in the detection of the specific position or flow junction leakage detection, factory workers simply handheld reader queries the sensor tag around the car, without artificial detection.

Compliance, safety, and EMI performance

Various semiconductor/configuration in different occasions with reader, antenna, and nine sensor tags based on CISPR 25 Class 3 test, through the outer area of transmission test, and in the rf transmission frequency range from 860 to 960 MHz maximum transmitted power for 33 dBm (about 2 W), to comply with the FCC Part 15 and FCC 47 cfr2:0 et (< 1 W), EMC meet CISPR 25 Class 3 specification, RFID area spectrum not cross other frequency interference.

Due to the intelligent passive sensor itself has no internal energy, it through the RF transmission reflection, so there is no safety concerns. Reader, because of its work in 860-960 MHZ UHF RFID frequency, conform to the international agreement of ISO/IEC 18000-6 - c standard, the low frequencies in the electromagnetic spectrum, are lower than those of the stereo of radiation hazard, and the system maximum output power (dbM) 33 2 W as big as a mobile transmission power, so there is no any safety and health risks.

Products can be ordered and suites

At present, various semiconductor provides the following types of intelligent passive sensor samples, and based on AMS RFID IC + 8 bits MCU + CAN transceiver reader reference design, 3 to 6 dBi UHF antenna reference design, effective reading distance as well as the system simulation model, antenna placement optimization advice, open source code and basic/advanced function development kit.

Semiconductor manufacturing initiative passive sensor intelligent power the development of smart car 6

conclusion

As the world's second largest non microcontroller car semiconductor supplier, passing on 50 years of experience in automotive semiconductor, semiconductor manufacturing continues to push the car in the field of efficient innovation, the company recently launched the intelligent passive sensor is the world's first passive, no additional single chip microcomputer control of intelligent sensor, single chip, enhance the level of auto intelligent controller sensing, passive wireless features to reduce the vehicle wiring harness. Chip internal integration special data processing temperature, humidity, pressure, distance and the kernel of sensors, such as the need batteries, ultra-thin, ultra small volume, low cost features make it can be used for difficult to contact position, limited space and needs of the application of multiple sensor function, such as seat detection, liquid level detection, wiper, tire pressure monitoring, vehicle leakage detection, etc., the installation position of the flexible and can be customized size and function design of the power to the development of smart car.