Austin, Tex. Freescale Semiconductor has unveiled at the Freescale Technology Forum in Tokyo what it says is the industry's first tire pressure monitoring system (TPMS) containing a capacitive pressure sensor for ultra-low-power consumption and precise sensing. "By using capacitive sensor technology, in addition to the small size, we get low power consumption, and we can now provide a two-axis accelerometer with self-testing, which is unique," said Mark Shaw, senior member technical staff at Freescale.
Designed for automobiles and medium- to heavy-duty trucks, the MPXY8300 system-in-package device provides a highly integrated and low-cost system that combines a pressure sensor, an 8-bit microcontroller (MCU), 2-axis accelerometer and radio frequency (RF) transmitter in a 20-pin SOIC wide body package. (See diagram.)
A key driver behind its development is the National Highway Traffic Safety Administration's (NHTSA) regulations that require all new vehicles weighing up to 10,000 pounds to include TPMS technology by the model year 2008. Similar safety regulations are expected in Europe and Asia-Pacific.
Automotive safety is the number one growth driver for automotive electronics systems, according to Strategy Analytics, with legislation driving safety growth in areas of TPMS and occupant detection. (See automotive safety growth chart and market size.)
While the NHTSA regulation is very basic and there are no standards for TPMS systems, the need for greater product differentiation is driving requirements for higher accuracy, higher precision and more flexibility, said Eric Caron, product marketing for TPMS at Freescale.
The MPXY8300 TPMS solution is designed to help drivers maintain proper tire pressure by instantly notifying them when any individual tire (including the spare) is not at the optimal pressure level. Engineered for wheel-mounted applications, the MPXY8300 system offers precise, real-time tire pressure measurement using direct monitoring at each wheel together with an integrated accelerometer for motion detection. Making the device more flexible, the system can be programmed to transmit measurements at certain tire rotation speeds and even when the tires are not rotating at all, said Freescale.
Key components of the MPXY8300 system-in-package device include the
pressure and temperature sensors for compensating tire pressure, XZ-axis accelerometer, RF transmitter with integrated charge pump at 315/434 MHz, low-frequency input for receiving diagnostic commands, and an 8-bit MCU with 512b RAM, 16 KB flash (8KB dedicated to firmware) and multiple low-power timing functions. It also incorporates several low-power techniques to help extend the battery-life beyond the ten-year requirements.
Other key features include two pressure range options of 100 to 800 kPa for passenger cars and 100 to 1500 kPa for heavy-duty trucks, multiple baud rate and modulation scheme, a low-power wake-up timer and periodic reset driver, and an integrated filter design for media protection in harsh vehicle environments.
In addition to the benefit of using a single-chip solution, which reduces cost and eases development time, the Freescale product can be easily modified by application and is available in several versions.
"It's a single package solution that reduces size, cost and development time. It's also highly flexible compared to what you see in the market; you can do every thing with this part that we see required. We also provide all the routines to do the more complicated tasks of making the measurement and compensating it, and handling some of the hardware issues," said Shaw.
"By taking our expertise and capacity in MEMS and applying it to pressure and acceleration for TPMS we can provide a product with a dual-axis accelerometer. We can also provide it with a variety of levels so customers have different ways of implementing their system from basic to very complex," said Shaw.
(See selector guide.)
"Because we provide the firmware with high level software commands it stays simple and easy to use," added Caron.
Availability: MPXY8300 samples are available now to select customers, and general market availability is expected in the second quarter of 2008. Freescale plans to offer several development tools in the second quarter of 2008. These tools will contain firmware drivers to speed application development. Key high-level software commands include reading pressure, acceleration, temperature, and battery voltage and interface with the RF transmitter.
Pricing: Suggested per-unit resale pricing in quantities of 10,000:
- MPXY8300A for passenger cars with XZ-axis accelerometer at $6.60
- MPXY8300B for passenger cars with Z-axis accelerometer at $5.48
- MPXY8300C for passenger cars without an accelerometer at $5.22
- MPXY8320A for heavy duty trucks with XZ-axis accelerometer at $9.64
- MPXY8320B for heavy duty trucks with Z-axis accelerometer at $8.00
- MPXY8320C for heavy duty trucks without an accelerometer at $7.63
Product information: TPMS
Freescale Semiconductor, 1-800-521-6274, www.freescale.com