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PDF MPXY8021A6T1 Data sheet ( Hoja de datos )
| Número de pieza | MPXY8021A6T1 | |
| Descripción | Tire Pressure Monitoring Sensor | |
| Fabricantes | Motorola Inc | |
| Logotipo |  |
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Freescale Semiconductor, Inc.
MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
Order Number: MPXY8021A
Rev. 0, 07/2004
Tire Pressure Monitoring Sensor
Temperature Compensated and
Calibrated, Fully Integrated,
Digital Output
MPXY8021A
General Description
The Motorola MPXY8021A sensor 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 MPXY8021A sensor 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.
TIRE PRESSURE
MONITORING SENSOR
MPXY8021A:
OPTIMIZED FOR 250 kPa – 450 kPa
SUPER SMALL OUTLINE PACKAGE
CASE 1352-03
PIN ASSIGNMENT
S1/VPP 1
VDD 2
VSS 3
OUT 4
8 SO
7 CLK
6 DATA
5 RST
8-pin Super Small Outline Package (SSOP)
ORDERING INFORMATION
Shipped In Rails
Shipped in Tape &
Reel
MPXY8021A6U
MPXY8021A6T1
REV 0
© Motorola, Inc. 2004
For More Information On This Product,
Go to: www.freescale.com
1 page  
Freescale Semiconductor, Inc.
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 Figure 5. 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 whenever 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.
Function
Voltage Comparator Threshold Adjust (8 bits)
Table 2. D/A Threshold Bit Assignment
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 reduce
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
undefined following power up of the device. The serial bit
counter can be reset by cycling either the SO pin or the S1/VPP
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.
CLK
Data
1 2345678
MSB
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
LSB
Serial Data ∗
MSB
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
LSB
DAR Load *
DAR *
Data
(*) Denotes Internal Signal
Figure 5. Serial Data Timing
Pressure Sensor Output
Temperature Sensor Output
The pressure channel compares the output of its analog
measurement circuit to the D/A reference voltage. The device is
calibrated at two different nominal values depending on the
calibration option.
The temperature channel compares the output of a positive
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
MPXY8021A
5
5 Page 
Freescale Semiconductor, Inc.
SENSOR CHARACTERISTICS (MPXY8021A)
Pressure Error
30.0
25.0
20.0
15.0
10.0
5.0
0.0
50
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
2.1
100 150 200 250 300 350 400 450 500
Pressure [kPa]
Figure 9. Pressure Error vs Pressure at T = 25°C, 2.7 V ≤ VDD ≤ 3.3 V
2.3 2.5 2.7 2.9 3.1 3.3
VDD [V]
Figure 10. Pressure Error vs VDD at T = 25°C, 250 kPa ≤ P ≤ 450 kPa
550 600
3.5
30.0
25.0
20.0
15.0
10.0
5.0
0.0
50
100 150 200 250 300 350 400 450 500 550 600 650
Pressure [kPa]
Figure 11. Pressure Error vs Temperature at VDD = 3.0 V, 250 kPa ≤ P ≤ 450 kPa
700
Motorola Sensor Device Data
For More Information On This Product,
Go to: www.freescale.com
MPXY8021A
11
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