Atmel Monitors Tire Pressure with Very Low-Current Transmitter ICs

4/8/2004 - Atmel® Corporation (Nasdaq: ATML) announced the availability of two new UHF ASK/ FSK transmitter ICs optimized for use in battery-powered Tire Pressure Monitoring System (TPMS) modules. The ATA5756 is designed for applications in the 315-MHz range (North America), while the ATA5757 is dedicated for 433 MHz (Europe), but can also be operated at 448 MHz as typically requested for the Korean market.

Thanks to their very short settling time and low active current consumption, the new TPMS ICs help to drastically reduce the total current consumption and thus to extend the modules' life time. This is mandatory for TPMS applications since TPMS modules mounted on the rim of vehicle wheels, transmitting continuously tire pressure data to the vehicle's body, must guarantee an overall life time of 10 years.

The ATA5756's and the ATA5757's settling time is less than 0.85 ms (typically), thus saving battery power especially in TPMS sensor boards. This makes the devices also well suited for PEG (Passive Entry Go) key fobs where quick reaction times on protocols is a main requirement.

Another feature that helps to extend the module's lifetime is the low current consumption. The typical current consumption during transmission mode (PA ON) is 8.1 mA with a typical output power of 6 dBm. During power-down mode, the typical current consumption is as low as 1 nA.

To extend the module's lifetime, TPMS systems also require, when operating at very low temperatures, low operation voltages of 2.0 V with flexible transmission duty cycle modes. In contrast to competing devices that are only capable of 2.1 V operation at low temperatures, Atmel's transmitter ICs ATA5756 and ATA5757 provide guaranteed 2 V operation at -40 degree Celsius/F.

The 3-wire-compatible interface allows connecting additional devices, such as an LF receiver, in parallel to the microcontroller ports, thus enabling flexible TPM sensor board designs. Conventional TPMS transmitter ICs without 3-wire-compatible interface need additional ports at the microcontroller.

Another disadvantage of conventional TPMS transmitter ICs is that their oscillation margin is not sufficient, which may cause the quartz to fail, resulting in a complete breakdown of the sensor board. To avoid this and to ensure proper detection of the XTO amplitude, the effective series resonance resistance of the XTAL is defined at 150 Ohm maximum, and the oscillation margin has been increased. The negative resistance of the XTO is specified with -1100 Ohm.

The devices use state-of-the-art 13 MHz crystals for operation which allow small crystal packages. The VCO is locked at 24 x fXTAL (315 MHz) and at 32 x fXTAL (433.92 MHz), respectively.

The PLL transmitter ICs can be used in ASK and FSK systems with 20 kBaud Manchester or 40 kBaud NRZ coding schemes. In FSK applications, only 7 external passive components need to be applied. The PLL loop filter as well as further PLL and VCO peripheral elements are fully integrated.

Atmel offers these new transmitter ICs in small-outline TSSOP10 packages, whereas competing devices come in larger packages.

Samples of the new TPMS transmitter ICs ATA5756 and ATA5757 small-outline TSSOP10 packages are available now. Pricing starts at US$1.10 (10 k).

ASK = Amplitude Shift Keying
FSK = Frequency Shift Keying
PEG = Passive Entry Go
PLL = Phase-Locked Loop
LF = Low Frequency
NRZ = Non-Return-to-Zero
TPMS = Tire-Pressure Monitoring System
UHF = Ultra-High Frequency
VCO = Voltage-Controlled Oscillator
XTAL = Crystal

About Atmel
Founded in 1984, Atmel Corporation is headquartered in San Jose, California with manufacturing facilities in North America and Europe. Atmel designs, manufactures and markets worldwide, advanced logic, mixed-signal, nonvolatile memory and RF semiconductors. Atmel is also a leading provider of system-level integration semiconductor solutions using CMOS, BiCMOS, SiGe, and high-voltage BCDMOS process technologies.

Atmel® and combinations thereof are the registered trademarks of Atmel Corporation or its subsidiaries.

Atmel's UHF ASK/ FSK transmitter IC ATA5756 and ATA5757 information may be retrieved at: (ATA5756) (ATA5757)

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