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Motorola Sensor Device Data

Tire Pressure Monitoring Sensor

Temperature Compensated and

Calibrated, Fully Integrated,

Digital Output

GENERAL DESCRIPTION

The Motorola MPXY8020A is an 8–pin tire monitoring sensor which is

comprised of a variable capacitance pressure sensing element, a temperature

sensing element, and an interface circuit (with a wake–up feature) all on a

single chip. It is housed in a Super–Small Outline Package (SSOP), which

includes a media protection filter. Specifically designed for the low power

consumption requirements of tire pressure monitoring systems, it can combine

with a Motorola remote keyless entry (RKE) system to facilitate a low–cost

highly integrated system.

Detailed Description

The block diagram of the MPXY8020A is shown in Figure 1. The pressure

sensor is a capacitive transducer constructed using surface micromachining,

the temperature sensor is constructed using a diffused resistor, and the

interface circuit is integrated onto the same die as the sensors using a standard

silicon CMOS process.

The conditioning of the pressure signal begins with a capacitance to voltage

conversion (C to V) followed by a switched capacitor amplifier. This amplifier

has adjustable offset and gain trimming. The offset and gain are factory

calibrated, with calibration values stored in the EEPROM trim register. This

amplifier also has temperature compensation circuits for both sensitivity and

offset, which also are factory–adjusted using the EEPROM trim register.

The pressure is monitored by a voltage comparator, which compares the

measured value against an 8–bit threshold adjusted by a serial input. By

adjusting the threshold and monitoring the state of the OUT pin the external

device can check whether a low–pressure threshold has been crossed, or

perform up to 8–bit A/D conversions.

The temperature is measured by a diffused resistor with a positive

temperature coefficient driven by a current source, thereby creating a voltage.

The room temperature value of this voltage is factory–calibrated using the

EEPROM trim register. A two–channel multiplexer can route either the

pressure or temperature signal to a sampling capacitor that is monitored by a

voltage comparator with variable threshold adjust, providing a digital output for

temperature.

An internal low frequency, low power 5.4 kHz oscillator with a 14–stage

divider provides a periodic pulse to the OUT pin (divide by 16384 for 3

seconds). This pulse can be used to wake up an external MCU to begin an

interface with the device. An additional 10–stage divider will provide a pulse

every 52 minutes which can be used to reset an external MCU.

The power consumption can be controlled by several operational modes

selected by external pins.

REV 1.0

Order this document

by MPXY8020A/D

MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

MPXY8020A

SUPER SMALL OUTLINE PACKAGE

CASE 1352

ORDERING INFORMATION

Shipped in Rails

Shipped in Tape & Reel

MPXY8020A6U

MPXY8020A6T1

TIRE PRESSURE MONITORING

SENSOR

OPTIMIZED FOR 250 kPa – 450 kPa

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com