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PDF MPXY8020A Data sheet ( Hoja de datos )
| Número de pieza | MPXY8020A | |
| Descripción | Tire Pressure Monitoring Sensor | |
| Fabricantes | Motorola Semiconductors | |
| Logotipo |  |
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MOTOROLA
Freescale Semiconductor, Inc.
SEMICONDUCTOR TECHNICAL DATA
Order this document
by MPXY8020A/D
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.
MPXY8020A
TIRE PRESSURE MONITORING
SENSOR
OPTIMIZED FOR 250 kPa – 450 kPa
SUPER SMALL OUTLINE PACKAGE
CASE 1352
ORDERING INFORMATION
Shipped in Rails Shipped in Tape & Reel
MPXY8020A6U
MPXY8020A6T1
REV 1.0
©
Motorola Sensor
Motorola, Inc. 2003
Device
Data
For More Information On This Product,
Go to: www.freescale.com
1
1 page  
Freescale Semiconductor, Inc.
MPXY8020A
Output Threshold Adjust
The state of the OUT pin is driven by a voltage comparator
whose output state depends on the level of the input voltage
on the sample capacitor and the level of an adjustable 8–bit
threshold voltage. The threshold is adjusted by shifting data
bits into the D/A Register (DAR) via the DATA pin while
clocking the CLK pin. The timing of this data is shown in Fig-
ure 6. Data is transferred into the serial shift register on the
rising edge of the CLK pin. On the falling edge of the 8th
clock the data in the serial shift register is latched into the
parallel DAR register. The DAR remains powered up when-
ever VDD is present. The serial data is clocked into the DATA
pin starting with the MSB first. This sequence of threshold
select bits is shown in Table 2.
Table 2. D/A Threshold Bit Assignments
Function
Voltage Comparator Threshold Adjust (8 bits)
LSB
MSB
Bit Weight
1
2
4
8
16
32
64
128
Data Bit
D0
D1
D2
D3
D4
D5
D6
D7
An analog to digital (A/D) conversion can be accomplished
with eight (8) different threshold levels in a successive
approximation algorithm; or the OUT pin can be set to trip at
some alarm level. The voltage on the sample capacitor will
maintain long enough for a single 8–bit conversion, but may
need to be refreshed with a new measured reading if the
read interval is longer than the specified hold time, tSH.
The counter that determines the number of clock pulses
into the device is reset whenever the device is placed into the
Measure Pressure or Measure Temperature Modes. This
provides a means to reset the data transfer count in case the
clock stream is corrupted during a transmission. In these two
modes the DATA and CLK pins should not be clocked to re-
duce noise in the captured pressure or temperature data.
Any change in the DAR contents should be done during the
Standby or Output Read Modes.
Both the serial bit counter and the state of the DAR are un-
defined following power up of the device. The serial bit count-
er can be reset by cycling either the SO pin or the S1 pin to a
high level and then back low. The DAR can then be reset to
the lowest level by holding the DATA pin low while bursting
the CLK pin with eight (8) clock pulses.
1 23 4 5 6 78
CLK
Data
MSB BIT6 BIT5
BIT4 BIT3
BIT2 BIT1
LSB
Serial Data ∗
MSB BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 LSB
DAR Load *
DAR *
( * ) Denotes Internal Signal
Figure 6. Serial Data Timing
Data
Pressure Sensor Output
The pressure channel compares the output of its analog
measurement circuit to the D/A reference voltage. The de-
vice is calibrated at two different nominal values depending
on the calibration option.
Temperature Sensor Output
The temperature channel compares the output of a posi-
tive temperature coefficient (PTC) resistor driven by a
switched current source. The current source is only active
when the temperature channel is selected.
Motorola Sensor Device Data For More Information On This Product,
Go to: www.freescale.com
5
5 Page 
Freescale Semiconductor, Inc.
SENSOR CHARACTERISTICS (MPXY8020A)
Pressure Error
30.0
MPXY8020A
25.0
20.0
15.0
10.0
5.0
0.0
50
100
35
30
25
20
15
10
150 200 250 300 350 400 450 500
Pressure [kPa]
Figure 9. Pressure Error vs Pressure at T= 255C, 2.7 3 VDD 3 +3.3 V
550 600
5
0
2.1
35.0
2.3 2.5
2.7 2.9
Vdd [V]
3.1
3.3
Figure 10. Pressure Error vs VDD at 255C, 250 kPa 3 P 3 450 kPa
3.5
30.0
25.0
20.0
15.0
10.0
5.0
0.0
–40.0
–20.0
0.0
20.0 40.0 60.0 80.0 100.0
120
Temperature [C]
Figure 11. Pressure Error vs. Temperature at VDD = 3 V, 250 kPa 3 P 3 450 kPa
Motorola Sensor Device Data For More Information On This Product,
Go to: www.freescale.com
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MPXY8020A.PDF ] | |
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