AN238 Microchip Technology Inc., AN238 Datasheet
AN238
Available stocks
Related parts for AN238
AN238 Summary of contents
Page 1
... FIGURE 1: TIRE PRESSURE MONITORING (TPM) SYSTEM 2004 Microchip Technology Inc. AN238 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 ...
Page 2
... AN238 Sensor/Transmitter (S/TX) Device There are typically five S/TX units per vehicle, one per wheel, and the spare tire. Each unit has a unique serial number enabling the system to distinguish between each tire. When mounted within a vehicle tire, the S/TX periodically measures internal tire pressure, tempera- ture and battery condition ...
Page 3
... The transmit power can be changed per the “Power Select Resistor Select” table located in the “rfPIC12F675” Data Sheet (DS70091). This is also useful when trying to certify a product to FCC regulations 220 120 nH XTAL ANT AN238 ™ Y1 9.84375 100 pF DS00238B-page 3 ...
Page 4
... AN238 Sensonor SP-13 Sensor IC The SP-13 sensor IC performs several functions. It measures pressure, temperature, and generates a flag when the battery voltage drops below a predetermined threshold. The SP-13 has five unique modes: 1. Storage mode: If the pressure is below 1.5 bar, pressure is measured every 60 seconds but no data is sent ...
Page 5
... Status: This status byte contains the following informa- tion: 8 Bits 0 and 1: Indicate operating state of sensor Initial or Storage mode 01 = Normal mode 10 = Pressure Alert mode 11 = Temperature Alert mode CRC (2 bytes): Implement according to CCITT standards. AN238 LF Out D2 Schottky 1000 pF DS00238B-page 5 ...
Page 6
... AN238 LF Commander THEORY OF OPERATION The system proposed in this document is based on an auto-location system, enabling it to detect the position of a specific S/TX device. This requires a LF commander device at each wheel arc and possibly at the spare tire mounting position. Having a handheld LF commander unit can enable a lower cost system ...
Page 7
... FIGURE 7: PHOTOGRAPH OF SENSOR/TRANSMITTER DEVICE 2004 Microchip Technology Inc. AN238 DS00238B-page 7 ...
Page 8
... AN238 REFERENCE DOCUMENTS The following reference documents are available from Microchip's web site at www.microchip.com. 1. “Low Frequency Magnetic Transmitter Design” Application Note (AN232), DS00232; Microchip Technology Inc. 2. “Designing Loop Antennas for the rfPIC12F675” Application Note (AN868), DS00868; Microchip Technology Inc. ...
Page 9
... APPENDIX A: SCHEMATICS FIGURE A-1: TPM SENSOR/TRANSMITTER SCHEMATIC 2004 Microchip Technology Inc. AN238 DS00238B-page 9 ...
Page 10
... AN238 NOTES: DS00238B-page 10 2004 Microchip Technology Inc. ...
Page 11
... Use of Microchip’s products as critical components in life support systems is not authorized except with express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights. 2004 Microchip Technology Inc. Trademarks The Microchip name and logo, the Microchip logo, Accuron, dsPIC ...
Page 12
... Via Quasimodo, 12 20025 Legnano (MI) Milan, Italy Tel: 39-0331-742611 Fax: 39-0331-466781 Netherlands Biesbosch 14 NL-5152 SC Drunen, Netherlands Tel: 31-416-690399 Fax: 31-416-690340 United Kingdom 505 Eskdale Road Winnersh Triangle Wokingham Berkshire, England RG41 5TU Tel: 44-118-921-5869 Fax: 44-118-921-5820 01/26/04 2004 Microchip Technology Inc. ...