Pressure
Freescale Semiconductor Miniature I2C Digital Barometer
The MPL115A2 is an absolute pressure sensor with digital output for low cost applications. A miniature 5 x 3 x 1.2 mm LGA package ideally suits it for portable electronics and space constrained applications. Low current consumptions of 5 μA during Active mode and 1 μA during Shutdown (Sleep) mode target battery and other low-power applications. A wide operating temperature range from -40°C to +105°C fits demanding environmental requirements. MPL115A2 employs a MEMS pressure sensor with a conditioning IC to provide accurate pressure measurement from 50 to 115 kPa. An integrated ADC provides digitized temperature and pressure sensor outputs via an I2C port. Calibration Data is stored in internal ROM. Utilizing raw sensor output, the host microcontroller executes a compensation algorithm to render Compensated Absolute Pressure with 1 kPa accuracy. The MPL115A2 pressure sensor’s small form factor, low power capability, precision, and digital output optimize it for barometric measurement applications.
MPL115A2 Rev 5, 08/2009
MPL115A2
50 to 115 kPa
Application Examples
• • • • • • • Barometry (portable and desk-top) Altimeters Weather Stations Hard Disk-Drives (HDD) Industrial Equipment Health Monitoring Air Control Systems
Features
• Digitized pressure and temperature information together with programmed calibration coefficients for host micro use. • Factory Calibrated • 50 kPa to 115 kPa Absolute Pressure • 1 kPa Accuracy • 2.375 V to 5.5 V Supply • Integrated ADC • I2C Interface • Monotonic Pressure and Temperature Data Outputs • Surface Mount RoHS Compliant Package ORDERING INFORMATION
Device Name MPL115A2T1 Package Options Tape & Reel Case No. 2015 # of Ports None • Single Dual
Pressure Type Gauge Differential Absolute •
Digital Interface I2 C
LGA PACKAGE
Pin Description
PIN 1 2 MPL115A2 5.0 mm X 3.0 mm X 1.2 mm MAX
VDD CAP GND SHDN 1 2 3 4 8 7 6 5 SCL SDA NC RST
NAME VDD CAP GND SHDN RST NC SDA(1) SCL(1)
FUNCTION VDD Power Supply Connection. External Capacitor Ground Shutdown (Sleep): Connect to GND to disable the device. Reset: Drive line low to disable I2C communications. NC: No connection. SDA: Serial data I/O line. I2C Serial Clock Input.
3 4 5 6 7 8
1. Use 4.7k pull-up resistors for I2C communication.
PIN CONNECTIONS
© Freescale Semiconductor, Inc., 2009. All rights reserved.
Pressure
Maximum Ratings
Voltage (with respect to GND unless otherwise noted) VDD .............................................................................................................................. -0.3 V to +5.5 V SCLK, CS, DIN, DOUT ................................................................................................. -0.3 V to VDD+0.3 V Operating Temperature Range .................................................................................... -40°C to +105°C Storage Temperature Range........................................................................................ -40°C to +125°C Overpressure ............................................................................................................... 1000 kPa
Operating Characteristics
(VDD = 2.375 V to 5.5 V, TA = -40°C to +105°C, unless otherwise noted. Typical values are at V+ = 3.3 V, TA = +25°C. Ref 1 2 Parameters Operating Supply Voltage Supply Current Symbol VDD IDD Shutdown (SHDN = GND) Standby Average – at one measurement per second Pressure Sensor 3 4 5 6 Range Resolution Accuracy Power Supply Rejection -20ºC to 85ºC Typical operating circuit at DC 100 mV p-p 217 Hz square wave plus 100 mV pseudo random noise with 10 MHz bandwidth. 7 Conversion Time (Start Pressure Convert) tcp Time between start convert command and data available in the Pressure register 50 — — — — — — 0.15 ±1 0.1 0.1 0.6 115 — — — — 0.7 kPa kPa kPa kPa/V kPa ms Conditions Min 2.375 — — — Typ 3.3 — 3.5 5 Max 5.5 1 10 6 Units V μA μA μA
Temperature Sensor 8 9 10 Range Conversion Time (Start Temperature Convert) Conversion Time (Start Both Convert) Resolution tct tcb Time between start convert command and data available in the Temperature register Time between start convert command and data available in the Pressure and Temperature registers Temperature ADC is 472 counts at 25ºC -40 — — — 0.6 0.8 105 0.7 1 ºC ms ms
11
—
-5.35
—
counts/ºC
I2C I/O Stages: SCL, SDA 12 13 14 SCL Clock Frequency Low Level Input Voltage High Level Input Voltage fSCL VIL VIH — — 0.7VDD — — — 400 0.3VDD — KHz V V
I2C Outputs: SDA 15 Data Setup Time tSU Setup time from command receipt to ready to transmit 100 — — ns
I2C Addressing MPL115A2 uses 7-bit addressing, does not acknowledge the general call address 0000000. Slave address has been set to 0x60 or 1100000.
MPL115A2 2 Sensors Freescale Semiconductor
Pressure
VDD VDD
1 μF
ADDR
Coefficient Storage Diff Amp MUX ADC
ADDR
CAP CAP
1 μF
ADDR
ADDR ADDR
Pressure Temperature
SHDN SHDN 4.7 k
Temp Sensor I 2C Interface
SCL SCL SDA SDA RST RST GND GND
μC
4.7 k Microcontroller
Figure 1. Block Diagram
Compensation
The pressure compensation for MPL115A2 is based on a 2-dimensional, second order polynomial. The 10-bit compensated pressure output, Pcomp, is calculated as follows: Pcomp = a0 + (b1 + c11*Padc + c12*Tadc) * Padc + (b2 + c22*Tadc) * Tadc Where: Padc is the 10-bit pressure output of the MPL115A2 ADC, Tadc is the 10-bit temperature output of the MPL115A2 ADC, a0 is the pressure offset coefficient, b1 is the pressure sensitivity coefficient, c11 is the pressure linearity (2nd order) coefficient, c12 is the coefficient for temperature sensitivity coefficient (TCS), b2 is the 1st order temperature offset coefficient (TCO), c22 is the 2nd order temperature offset coefficient. Ideally, Pcomp will produce a value of 0 with an input pressure of 50 kPa and will produce a full-scale value of 1023 with an input pressure of 115 kPa.
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Pressure
Coefficient Bit-Width Specs
The table below specifies the initial coefficient bit-width specs for the compensation algorithm.
Total Coeff. Bits 84
10-bit Output: Compensation Coefficient Specs a0 Total Bits Sign Bits Integer Bits Fractional Bits dec pt zero pad 16 1 12 4 — b1 16 1 2 13 — b2 16 1 1 14 — c12 14 1 0 13 9 c11* 11 1 0 11 11 c22* 11 1 0 10 15
* Factory reserves the option to make these values = 0.
Example Binary Format Definitions:
1. 2. 3. 4.
Sign = 0, Integer Bits = 8, Fractional Bits = 4 : Sign = 1, Integer Bits = 4, Fractional Bits = 7 :
Coeff = S I7 I6 I5 I4 I3 I2 I1 I0 . F3 F2 F1 F0 Coeff = S I3 I2 I1 I0 . F6 F5 F4 F3 F2 F1 F0
Sign = 0, Integer Bits = 0, Fractional Bits = 6, dec pt zero pad = 2 : Coeff = S 0 . 0 0 F5 F4 F3 F2 F1 F0 Sign = 0, Integer Bits = 0, Fractional Bits = 5, dec pt zero pad = 3 : Coeff = S 0 . 0 0 0 F4 F3 F2 F1 F0
NOTE: Negative coefficients (Sign = 1) are coded in 2’s complement notation.
Coefficient Address Map
Address $04 $05 $06 $07 $08 $09 $0A $0B $0C $0D $0E $0F Coefficient a0 MS Byte a0 LS Byte b1 MS Byte b1 LS Byte b2 MS Byte b2 LS Byte c12 MS Byte c12 LS Byte c11 MS Byte c11 LS Byte c22 MS Byte c22 LS Byte
For coefficients with less than 16 bits, the lower lsbs are zero. For example, c11 is 11 bits and is stored into 2 bytes as follows: c11 MS byte = c11[10:3] = [c11b10 , c11b9 , c11b8 , c11b7 , c11b6 , c11b5 , c11b4 , c11b3] c11 LS byte = c11[2:0] & “00000” = [c11b2 , c11b1 , c11b0 , 0 , 0 , 0 , 0 , 0]
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Solder Recommendations
1. 2. Use SAC solder alloy (i.e., Sn-Ag-Cu) with a melting point of about 217°C. It is recommended to use SAC305 (i.e., Sn-3.0 wt.% Ag-0.5 wt.% Cu). Reflow • • • • • • Ramp up rate: 2 to 3 C/s. Preheat flat (soak): 110 to 130s. Reflow peak temperature: 250°C to 260°C (depends on exact SAC alloy composition). Time above 217°C: 40 to 90s (depends on board type, thermal mass of the board/quantities in the reflow). Ramp down: 5 to 6 C/s. Using an inert reflow environment (with O2 level about 5 to 15 ppm).
NOTE: The stress level and signal offset of the device also depends on the board type, board core material, board thickness and metal finishing of the board.
Handling Recommendations
It is recommended to handle the MPL115A Pressure Sensor with a vacuum pick and place tool. Sharp objects utilized to move the MPL115A Pressure Sensor increase the possibility of damage via a foreign object/tool into the small exposed port. The sensor die is sensitive to light exposure. Direct light exposure through the port hole can lead to varied accuracy of pressure measurement. Avoid such exposure to the port during normal operation.
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PACKAGE DIMENSIONS
CASE 2015-02 ISSUE O LGA PACKAGE
MPL115A2 6 Sensors Freescale Semiconductor
Pressure
PACKAGE DIMENSIONS
CASE 2015-02 ISSUE O LGA PACKAGE
MPL115A2 Sensors Freescale Semiconductor 7
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MPL115A2 Rev. 5 08/2009
