ST LPS331AP User Manual

LPS331AP

MEMS pressure sensor: 260-1260 mbar absolute digital output

barometer

Datasheet − production data

Features

■ 260 to 1260 mbar absolute pressure range

■ High-resolution mode: 0.020 mbar RMS

■ Low power consumption:

– Low resolution mode: 5.5 – High resolution mode: 30

■ High overpressure capability: 20x full scale

■ Embedded temperature compensation

■ Embedded 24-bit ADC

■ Selectable ODR from 1 Hz to 25 Hz

■ SPI and I

■ Supply voltage: 1.71 to 3.6 V

■ High shock survivability: 10,000 g

■ Small and thin package

■ ECOPACK

C interfaces

lead-free compliant

Applications

■ Indoor and outdoor navigation

■ Enhanced GPS for dead-reckoning

■ Altimeter and barometer for portable devices

■ Weather station equipment

■ Sport watches

µA µA

HCLGA-16L

(3 x 3 x 1 mm)

The sensing element consists of a suspended membrane realized inside a single mono-silicon substrate. It is capable to detecting pressure and is manufactured using a dedicated process developed by ST, called VENSENS.

The VENSENS process allows to build a monosilicon membrane above an air cavity with controlled gap and defined pressure. The membrane is very small compared to the traditionally built silicon micromachined membranes. Membrane breakage is prevented by an intrinsic mechanical stopper.

The IC interface is manufactured using a standard CMOS process that allows a high level of integration to design a dedicated circuit which is trimmed to better match the sensing element characteristics.

Description

The LPS331AP is available in a small holed cap

land grid array (HCLGA) package and it is The LPS331AP is an ultra compact absolute piezoresistive pressure sensor. It includes a monolithic sensing element and an IC interface able to take the information from the sensing element and to provide a digital signal to the external world.

Table 1. Device summary

Order codes Temperature range [°C] Package Packing

LPS331APY

-40 to +85 HCLGA-16L

LPS331APTR Tape and reel

March 2012 Doc ID 022112 Rev 7 1/36

This is information on a product in full production.

guaranteed to operate over a temperature range

extending from -40 °C to +85 °C. The package is

holed to allow external pressure to reach the

sensing element.

Tr ay

www.st.com

Contents LPS331AP

Contents

1 Block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 LPS331AP block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.3 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.1 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2 IC interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.3 Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4 Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.1 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5 Digital interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.1 I2C serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.2 I2C serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.2.1 I2C operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5.3 SPI bus interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5.3.1 SPI read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.3.2 SPI write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5.3.3 SPI read in 3-wires mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6 Register mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7 Register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8 Package mechanical section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

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LPS331AP Block diagram and pin description

1 Block diagram and pin description

1.1 LPS331AP block diagram

Figure 1. LPS331AP block diagram

Vup

Vout

Vdown

Sensing

element

1.2 Pin description

Figure 2. Pin connection

MUX

Temperature

sensor

Sensor bias

Low noise

analog front end

ADC

+ digital filter

Vol tage and

current bias

compensation

DSP for temperature

Clock and timing

Pin 1 indicator

I2C

SPI

SCL/SPC

SDA/SDO/ SDI

SA0/SDO

AM08736V1

13 1

Bottom view

Doc ID 022112 Rev 7 3/36

AM08737V1

Block diagram and pin description LPS331AP

Table 2. Pin description

Pin# Name Function

1 Vdd_IO Power supply for I/O pins

2 NC Not connected

3 NC Not connected

SCL SPC

I2C serial clock (SCL) SPI serial port clock (SPC)

5 GND 0 V supply

SDA

SDI

SDO

SA0

8CS

C serial data (SDA) SPI serial data input (SDI) 3-wire interface serial data output (SDO)

SPI serial data output (SDO) I2C less significant bit of the device address (SA0)

SPI enable I2C/SPI mode selection (1: I2C mode; 0: SPI enabled)

9 INT2 Interrupt 2 (or data ready)

10 Reserved Connect to GND

11 INT1 Interrupt 1 (or data ready)

12 GND 0 V supply

13 GND 0 V supply

14 VDD Power supply

15 VCCA Analog power supply

16 GND 0 V supply

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LPS331AP Mechanical and electrical specifications

2 Mechanical and electrical specifications

Conditions at VDD = 2.5 V, T = 25 °C, unless otherwise noted.

2.1 Mechanical characteristics

Table 3. Mechanical characteristics

Symbol Parameter Test condition Min. Typ.

Top Operating temperature range -40 – 85 °C

Tfull

Full accuracy temperature range

0–80 °C

Pop Operating pressure range 260 – 1260 mbar

Pbits Pressure output data – 24 – bits

(1)

Max. Unit

Pres Pressure sensitivity – 4096 –

Paccrel

PaccT

Relative accuracy over pressure

Absolute accuracy pressure over temperature

(2)

(3)

P = 800 to 1100 mbar T= 25°C

P = 800 to 1100 mbar T = 0 ∼ +80 °C

– ± 0.1 ± 0.2 mbar

- 3.2 ± 22.6 mbar

Pnoise Pressure noise See Table 17.

LSB/ mbar

mbar RMS

Tbits Temperature output data – 16 – bits

Tres Temperature sensitivity – 480 – LSB/°C

Tacc Absolute accuracy temperature T= 0~+80 °C – ± 2– °C

1. Typical specifications are not guaranteed.

2. Characterization data. Parameter not tested at final test

3. Embedded pwl compensation.

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Mechanical and electrical specifications LPS331AP

2.2 Electrical characteristics

Table 4. Electrical characteristics

Symbol Parameter Test condition Min. Typ.

Vdd Supply voltage 1.71 – 3.6 V

Vdd_IO IO supply voltage 1.71 – 3.6 V

Supply current @ ODRp 1 Hz and

Idd

ODRt = 1Hz

IddPdn

1. Typical specifications are not guaranteed.

Table 5. Supply current at ODRp 1 Hz, ODRt 1 Hz

Supply current in power-down mode T = 25 °C

–0.5 – µA

Symbol RES_CONF (hex) Min. Typ. Max. Unit

73 – 5.5 –

75 – 6.6 –

(1)

Max. Unit

see Ta b le 5 µA

Idd

77 – 11.5 –

78 – 17.5 –

7A – 30.0 –

µA

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LPS331AP Mechanical and electrical specifications

2.3 Absolute maximum ratings

Stress above those listed as “Absolute maximum ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device under these conditions is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.

Table 6. Absolute maximum ratings

Symbol Ratings Maximum value Unit

Vdd Supply voltage -0.3 to 4.8 V

Vdd_IO I/O pins supply voltage -0.3 to 4.8 V

Vin Input voltage on any control pin -0.3 to Vdd_IO +0.3 V

P Overpressure 20 bar

ESD Electrostatic discharge protection 2 (HBM) kV

Note: Supply voltage on any pin should never exceed 4.8 V.

Storage temperature range -40 to +125 °C

STG

This is a mechanical shock sensitive device, improper handling can cause permanent damage to the part.

This is an ESD sensitive device, improper handling can cause permanent damage to the part.

Doc ID 022112 Rev 7 7/36

Functionality LPS331AP

3 Functionality

The LPS331AP is a high resolution, digital output pressure sensor packaged in an HCLGA holed package. The complete device includes a sensing element based on a piezoresistive Wheatstone bridge approach, and an IC interface able to take the information from the sensing element to the external world, as a digital signal.

3.1 Sensing element

An ST proprietary process is used to obtain a mono-silicon µ-sized membrane for MEMS pressure sensors, without requiring substrate to substrate bonding. When pressure is applied, the membrane deflection induces an imbalance in the Wheatstone bridge piezoresistances, whose output signal is converted by the IC interface.

Intrinsic mechanical stoppers prevent breakage in case of pressure overstress, ensuring measurement repeatability.

The pressure inside the buried cavity under the membrane is constant and controlled by process parameters.

3.2 IC interface

The complete measurement chain consists of a low-noise capacitive amplifier, which converts the resistive unbalance of the MEMS sensor into an analog voltage signal, and of an analog-to-digital converter, which translates the produced signal into a digital bitstream.

The converter is coupled with a dedicated reconstruction filter which removes the high frequency components of the quantization noise and provides low rate and high resolution digital words.

The pressure data can be accessed through an I particularly suitable for direct interfacing with a microcontroller.

3.3 Factory calibration

The IC interface is factory calibrated at three temperatures and two pressures for sensitivity and accuracy.

The trimming values are stored inside the device by a non-volatile structure. Whenever the device is turned on, the trimming parameters are downloaded into the registers to be employed during normal operation. This allows the user to employ the device without requiring any further calibration.

C/SPI interface making the device

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LPS331AP Application hints

4 Application hints

Figure 3. LPS331AP electrical connection

Vdd

TOP VIEW

SDA/SDI/SDO

1416

SDO/SA0

Res

10¬µ

100nF

GND

Digital signal from/to signal controller. Signal levels are defined through proper selection of Vdd_

Vdd_IO

SCL/SPC

The device core is supplied through the Vdd line. Power supply decoupling capacitors (100 nF ceramic, 10 µF aluminum) should be placed as near as possible to the supply pad of the device (common design practice).

The functionality of the device and the measured data outputs are selectable and accessible through the I

C/SPI interface. When using the I2C, CS must be tied high (i.e. connected to

Vdd_IO).

4.1 Soldering information

The HCLGA package is compliant with the ECOPACK® standard and it is qualified for soldering heat resistance according to JEDEC J-STD-020.

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Digital interfaces LPS331AP

5 Digital interfaces

5.1 I2C serial interface

The registers embedded in the LPS331AP may be accessed through both the I2C and SPI serial interfaces. The latter may be SW configured to operate either in 3-wire or 4-wire interface mode.

The serial interfaces are mapped onto the same pads. To select/exploit the I line must be tied high (i.e. connected to Vdd_IO).

Table 7. Serial interface pin description

Pin name Pin description

C interface, CS

SCL/

SPC

SDA/

SDI/

SDO

SA0/ SDO

SPI enable

C/SPI mode selection (1: I2C mode; 0: SPI enabled)

C serial clock (SCL)

I SPI serial port clock (SPC)

I2C serial data (SDA) SPI serial data input (SDI) 3-wire interface serial data output (SDO)

C less significant bit of the device address (SA0)

I SPI serial data output (SDO)

5.2 I2C serial interface

The LPS331AP I2C is a bus slave. The I2C is employed to write data into registers whose content can also be read back.

The relevant I

Table 8. Serial interface pin description

Transmitter The device which sends data to the bus

Receiver The device which receives data from the bus

Master

C terminology is given in Table 8.

Term Description

The device which initiates a transfer, generates clock signals and terminates a transfer

Slave The device addressed by the master

There are two signals associated with the I2C bus: the serial clock line (SCL) and the serial data line (SDA). The latter is a bi-directional line used for sending and receiving the data to/from the interface. Both lines have to be connected to Vdd_IO through pull-up resistors.

The I

C interface is compliant with fast mode (400 kHz) I2C standards as well as with the

normal mode.

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LPS331AP Digital interfaces

5.2.1 I2C operation

The transaction on the bus is started through a START (ST) signal. A start condition is defined as a HIGH to LOW transition on the data line while the SCL line is held HIGH. After this has been transmitted by the master, the bus is considered busy. The next byte of data transmitted after the start condition contains the address of the slave in the first 7 bits and the eighth bit tells whether the master is receiving data from the slave or transmitting data to the slave. When an address is sent, each device in the system compares the first seven bits after a start condition with its address. If they match, the device considers itself addressed by the master.

The slave address (SAD) associated to the LPS331AP is 101110xb. The SDO/SA0 pad can be used to modify the less significant bit of the device address. If the SA0 pad is connected to voltage supply, LSb is ‘1’ (address 1011101b), otherwise if the SA0 pad is connected to ground, the LSb value is ‘0’ (address 1011100b). This solution permits to connect and address two different LPS331APs to the same I

Data transfer with acknowledge is mandatory. The transmitter must release the SDA line during the acknowledge pulse. The receiver must then pull the data line LOW so that it remains stable low during the HIGH period of the acknowledge clock pulse. A receiver which has been addressed is obliged to generate an acknowledge after each byte of data received.

The I

C embedded in the LPS331AP behaves like a slave device and the following protocol must be adhered to. After the start condition (ST) a slave address is sent, once a slave acknowledge (SAK) has been returned, a 8-bit sub-address (SUB) will be transmitted: the 7 LSB represents the actual register address while the MSB enables address auto increment. If the MSb of the SUB field is ‘1’, the SUB (register address) will be automatically increased to allow multiple data read/write.

C lines.

The slave address is completed with a Read/Write bit. If the bit was ‘1’ (Read), a repeated START (SR) condition must be issued after the two sub-address bytes; if the bit is ‘0’ (Write) the master will transmit to the slave with direction unchanged. Tab l e 9 explains how the SAD+read/write bit pattern is composed, listing all the possible configurations.

Table 9. SAD+Read/Write patterns

Command SAD[6:1] SAD[0] = SA0 R/W SAD+R/W

Read 101110 0 1 10111001 (B9h)

Write 101110 0 0 10111000 (B8h)

Read 101110 1 1 10111011 (BBh)

Write 101110 1 0 10111010 (BAh)

Table 10. Transfer when master is writing one byte to slave

Master ST SAD + W SUB DATA SP

Slave SAK SAK SAK

Table 11. Transfer when master is writing multiple bytes to slave

Master ST SAD + W SUB DATA DATA SP

Slave SAK SAK SAK SAK

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