NPX1 - Tire Pressure Sensors

NPX1 Tire Pressure Sensor

NPX1 integrates a silicon pressure sensor, an 8-bit RISC processor, and a LF-input stage to meet market demands for flexible, customer specific behavior/solutions and overall system cost reduction for the Remote Tire Pressure Monitoring (RTPM) customer. The programmable version of this sensor is available for development purposes, allowing the customer to download the application code in an electrically programmable EEPROM version.

This tire pressure sensor is intended for developing the application specific program. In order to ensure high reliability, the NPX1 sensor has the measurement routines (pressure, temperature, and supply voltage) implemented in ROM.

 

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Features

  • 12 bit ADC
  • 4k byte flash (E-ROM)
  • 2k ROM for user application
  • 128 byte RAM
  • 128 byte EEPROM
  • Battery management—minimizing power consumption.
  • Measure and compensate pressure, temperature, and battery voltage
  • Media compatibility with tire pressure media
  • 450, 700, and 1400 kPa absolute pressure ranges.

custom ranges are available.

  • On chip temperature sensor
  • On chip temperature shut down

Applications

  • Tire pressure monitoring
  • Altimeters and barometers
  • Cable leak detection
  • Consumer appliances
  • Portable gauges and manometers

Specifications

General

Operating Temperature

-40°F to 257°F (-40°C to 125°C)

Storage Temperature -67°F to 257°F (-55°C to 125°C) Battery Supply Voltage

2.1 to 3.6 V (3.0 V typical)

Supply Current

400 :A


Pressure Ranges

100 to 450, 100 to 700, 0 to 1400 is typical

450 kPa Resolution

  • 1.37 kPa/LSB (450 kPa to 100 kPa/255)
  • -40°F to 257°F (-40°C to 125°C)

700 kPa Resolution

  • 2.35 kPa/LSB (700 kPa to 100 kPa/255)
  • -40°F to 257°F (-40°C to 125°C)

1400 kPa Resolution

  • 5.49 kPa/LSB (1400 kPa to 0 kPa/255)
  • -40°F to 257°F (-40°C to 125°C)

Over Pressure

10x

Pressure Measurement

Measurement Accuracy (2.1 to 3.6 V)

  • -6 to 6 LSB (6F capability), 32°F to 122°F (0°C to 50°C)
  • -8 to 8 LSB, -40°F to 257°F (-40°C to 125 °C)

NPX1-dig1


NPX-1-block

Preassure Measurement Charge Consumption (All Pressure Ranges)

3.2 micro-coulombs; 77°F (25°C), 3V

 

Battery Voltage Measurement

  • ±6 LSB, -40°F to 257°F (-40°C to 125°C)
  • 1 LSB = 10.8 mV/LSB
  • 0.4 micro-coulombs charge consumption

 

Temperature Measurement

Temperature Range
-40°F to 257°F (-40°C to 125°C)

Resolution
1.0 °C/LSB; 401°F -(-58°F)/255 (205°C -(-50°C)/255)

Measurement Accuracy (6F capability)

  • ±10.8°F (±6°C), -4°F to 158°F (-20°C to 70°C)
  • ±14.4°F (±8°C), -40°F to 257°F (-40°C to 125°C)


Measurement Charge Consumption (77°F (25°C), 3.0 V)

  • 0.8 micro-coulombs

 

Temperature Maximum


SHTD represents the temperature at which the thermal shut-down function can be enabled and ϑREL represents the temperature at which the master reset state is released.

SHTD

  • 239°F (115°C) maximum
  • 2.1 to 3.6 V
  • Thermal shut-down enabled

REL

  • 212°F(100°C) minimum
  • 2.1 to 3.6 V
  • Master reset release

Voltage Minimum


The voltage at which the Vmin-circuit will return a low battery voltage status is specified in:

Vmin

  • 2.0 to 2.2 V (2.1 V typical)
  • -40°F to 257°F (-40°C to 125°C)

 

Transfer Functions


450 kPa Pressure
P = 1.3725 x Po + 100
P = Pressure in kPa
Po = 8 bit scaled output pressure

700 kPa Pressure
P = 2.3529 x Po + 100
P = Pressure in kPa
Po = 8 bit scaled output pressure

1400 kPa Pressure
P = 5.490 x Po
P = Pressure in kPa
Po = 8 bit scaled output pressure

Temperature
T = To - 50
T = Temperature in °F (°C)
To = 8 bit scaled output temperature

V Battery
V = 0.0108 x Vo + 4
V = V Battery in V
Vo = 8 bit scaled output Vbattery

NPX1-Specs-Tb1

 
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