ST LPS331AP User Manual

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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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Digital interfaces LPS331AP

Table 12. Transfer when master is receiving (reading) one byte of data from slave

Master ST SAD + W SUB SR SAD + R NMAK SP

Slave SAK SAK SAK DATA

Table 13. Transfer when master is receiving (reading) multiple bytes of data from

slave

Master ST SAD+W SUB SR SAD+R MAK MAK NMAK SP

Slave SAK SAK SAK DATA DATA DATA

Data are transmitted in byte format (DATA). Each data transfer contains 8 bits. The number of bytes transferred per transfer is unlimited. Data is transferred with the most significant bit (MSb) first. If a receiver can’t receive another complete byte of data until it has performed some other functions, it can hold the clock line, SCL LOW to force the transmitter into a wait state. Data transfer only continues when the receiver is ready for another byte and releases the data line. If a slave receiver does not acknowledge the slave address (i.e. it is not able to receive because it is performing some real time function) the data line must be kept HIGH by the slave. The master can then abort the transfer. A LOW to HIGH transition on the SDA line while the SCL line is HIGH is defined as a STOP condition. Each data transfer must be terminated by the generation of a STOP (SP) condition.

In order to read multiple bytes incrementing the register address, it is necessary to assert the most significant bit of the sub-address field. In other words, SUB(7) must be equal to 1 while SUB(6-0) represents the address of the first register to be read.

In the presented communication format MAK is Master acknowledge and NMAK is no master acknowledge.

5.3 SPI bus interface

The LPS331AP SPI is a bus slave. The SPI allows to write and read the registers of the device.

The serial interface interacts with the outside world with 4 wires: CS, SPC, SDI and SDO.

Figure 4. Read and write protocol

SPC

SDI

SDO

AD5 AD4 AD3 AD2 AD1 AD0

DI7DI6DI5DI4DI3DI2DI1DI0

DO7DO6DO5DO4DO3DO2DO1DO0

CS is the serial port enable and it is controlled by the SPI master. It goes low at the start of the transmission and returns to high at the end. SPC is the serial port clock and it is controlled by the SPI master. It is stopped high when CS is high (no transmission). SDI and

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LPS331AP Digital interfaces

SDO are respectively the serial port data input and output. Those lines are driven at the

falling edge of SPC and should be captured at the rising edge of SPC.

Both the read register and write register commands are completed in 16 clock pulses or in multiples of 8 in the case of multiple bytes read/write. Bit duration is the time between two falling edges of SPC. The first bit (bit 0) starts at the first falling edge of SPC after the falling edge of CS while the last bit (bit 15, bit 23, ...) starts at the last falling edge of SPC just before the rising edge of CS.

bit 0: RW from the device is read. In the latter case, the chip will drive SDO at the start of bit 8.

bit 1: MS When 1, the address will be auto incremented in multiple read/write commands.

bit 2-7: address AD(5:0). This is the address field of the indexed register.

bit 8-15: data DI(7:0) (write mode). This is the data that is written into the device (MSb first).

bit 8-15: data DO(7:0) (read mode). This is the data that is read from the device (MSb first).

In multiple read/write commands further blocks of 8 clock periods are added. When the MS bit is 0 the address used to read/write data remains the same for every block. When MS is 1 the address used to read/write data is increased at every block.

The function and the behavior of SDI and SDO remain unchanged.

5.3.1 SPI read

Figure 5. SPI read protocol

bit. When 0, the data DI(7:0) is written into the device. When 1, the data DO(7:0)

bit. When 0, the address will remain unchanged in multiple read/write commands.

bit

SPC

SDI

AD5 AD4 AD3 AD2 AD1 AD0

SDO

DO7 DO6 DO5DO4 DO3 DO2 DO1DO0

The SPI Read command is performed with 16 clock pulses. The multiple byte read command is performed adding blocks of 8 clock pulses at the previous one.

bit 0: READ bit. The value is 1.

bit 1: MS

bit. When 0 do not increment address, when 1 increment address in multiple

reading.

bit 2-7: address AD(5:0). This is the address field of the indexed register.

bit 8-15: data DO(7:0) (read mode). This is the data that is read from the device (MSb first).

bit 16-... : data DO(...-8). Further data in multiple byte readings.

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Digital interfaces LPS331AP

Figure 6. Multiple bytes SPI read protocol (2 bytes example)

SPC

SDI

AD5 AD4 AD3 A D2 AD1 AD0

SDO

DO7DO6DO5DO4DO3DO2DO1DO0

DO15 DO14 DO13 DO12 DO11 DO10 DO9 DO8

5.3.2 SPI write

Figure 7. SPI write protocol

SPC

SDI

AD5 AD4 AD3 AD2 AD1 AD0MS

DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0

The SPI Write command is performed with 16 clock pulses. The multiple byte write command is performed adding blocks of 8 clock pulses at the previous one.

bit 0: WRITE bit. The value is 0.

bit 1: MS

bit. When 0 do not increment the address, when 1 increment the address in

multiple writings.

bit 2 -7: address AD(5:0). This is the address field of the indexed register.

bit 8-15: data DI(7:0) (write mode). This is the data that is written in the device (MSb first).

bit 16-... : data DI(...-8). Further data in multiple byte writings.

Figure 8. Multiple bytes SPI write protocol (2 bytes example)

SPC

SDI

AD5 AD4 AD3 AD2 AD1 AD0

DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0 DI15 DI14 DI13 DI12 DI11 DI10 DI9 DI8

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LPS331AP Digital interfaces

5.3.3 SPI read in 3-wires mode

A 3-wires mode is entered by setting to ‘1’ bit SIM (SPI serial interface mode selection) in CTRL_REG4.

Figure 9. SPI read protocol in 3-wires mode

SPC

SDI/O

AD5 AD4 AD3 AD2 AD1 AD0

The SPI read command is performed with 16 clock pulses:

bit 0: READ bit. The value is 1.

DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0

bit 1: MS

bit. When 0, do not increment the address, when 1, increment the address in

multiple readings.

bit 2-7: address AD(5:0). This is the address field of the indexed register.

bit 8-15: data DO(7:0) (read mode). This is the data that is read from the device (MSb first).

Multiple read command is also available in 3-wires mode.

Doc ID 022112 Rev 7 15/36

6 Register mapping

Ta bl e 1 4 provides a list of the 8-bit registers embedded in the device and the related

addresses.

Table 14. Registers address map

Name Type

Hex Binary

Reserved (Do not modify)

REF_P_XL R/W 08 0001000 00000000

REF_P_L R/W 09 0001001 00000000

REF_P_H R/W 0A 0001010 00000000

WHO_AM_I R 0F 0001111 10111011 Dummy register

RES_CONF R/W 10 0010000 011111010

Reserved (Do not modify) 11-1F Reserved

CTRL_REG1 R/W 20 010 0000 00000000

CTRL_REG2 R/W 21 010 0001 00000000

CTRL_REG3 R/W 22 010 0010 00000000

INT_CFG_REG R/W 23 0100011 00000000

INT_SOURCE_REG R 24 0100100 00000000

THS_P_LOW_REG R/W 25 0100101 0000000

THS_P_HIGH_REG R/W 26 0100110 0000000

STATUS_REG R 27 010 0111 00000000

00-07

0D - 0E

Default

Function and

comment

Reserved

PRESS_POUT_XL_REH R 28 010 1000 output

PRESS_OUT_L R 29 010 1001 output

PRESS_OUT_H R 2A 010 1010 output

TEMP_OUT_L R 2B 010 1011 output

TEMP_OUT_H R 2C 010 1100 output

Reserved (Do not modify) 2D-2F Reserved

AMP_CTRL R/W 30 011 0000 Partially reserved

Registers marked as Reserved must not be changed. The writing to those registers may cause permanent damages to the device.

The content of the registers that are loaded at boot should not be changed. They contain the factory calibration values. Their content is automatically restored when the device is powered-up.

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LPS331AP Register description

7 Register description

The device contains a set of registers which are used to control its behavior and to retrieve pressure and temperature data. The register address, made up of 7 bits, is used to identify them and to read/write the data through the serial interface.

REF_P_XL Reference pressure (LSB data)

76543210

REFL7 REFL6 REFL5 REFL4 REFL3 REFL2 REFL1 REFL0

Address: 08h

Type: R/W

Reset: 00h

Description: This reference pressure register contains the lower part of the reference pressure that

is sum to the sensor output pressure. The full value is REF_P_XL & REF_P_H & REF_P_L and is represented as 2’s complement.

[7:0] REFL7 - REFL0: Reference pressure LSB data. Default value: 00h

REF_P_L Reference pressure (middle part)

16 15 14 13 12 11 10 9

REFL15 REFL14 REFL13 REFL12 REFL11 REFL10 REFL9 REFL8

Address: 09h

Type: R/W

Reset: 00h

Description: This register contains the middle part of the reference pressure that is sum to the

sensor output pressure. The full value is REF_P_XL & REF_P_H & REF_P_L and is represented as 2’s complement.

[16:9] REFL15 - REFL8: Default value: 00h

Doc ID 022112 Rev 7 17/36

REF_P_H Reference pressure (MSB data)

24 23 22 21 20 19 18 17

REFL23 REFL22 REFL21 REFL20 REFL19 REFL18 REFL17 REFL16

Address: 0Ah

Type: R/W

Reset: 00h

Description: This register contains the higher part of the reference pressure that is sum to the

sensor output pressure. The full value is REF_P_XL & REF_P_H & REF_P_L and is represented as 2’s complement.

[24:17] REFL23 - REFL16: Reference pressure MSB data. Default value: 00h.

RES_CONF(10h) Pressure resolution mode

76543210

RFU AVGT2 AVGT 1 AVGT0 AVGP 3 AVGP2 AVGP1 AVGP0

Address: 10h

Type: R/W

Reset: 7Ah

Description: AVGP3-AVGP0 allow to select the pressure internal average. AVGT2-AVGT0 allow to

select the temperature internal average. AVGP3-AVGP0 bits can be configured as described in Ta b le 1 5 . AVGT2-AVGT0 bits can be configured as described in Tab le 1 6 .

Table 15. Pressure resolution configuration

AVGP3 AVGP2 AVGP1 AVGP0 Nr. internal average

0000 1

0001 2

0010 4

0011 8

0100 16

0101 32

0110 64

0111 128

1000 256

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LPS331AP Register description

Table 15. Pressure resolution configuration

AVGP3 AVGP2 AVGP1 AVGP0 Nr. internal average

1001 384

1010 512

1. Register configuration 7Ah not allowed with ODR = 25Hz/25Hz (Register CTRL_REG1). For ORD

25Hz/25Hz the suggested configuration for RES_CONF is 6Ah.

(1)

Table 16. Temperature resolution configuration

AVGT2 AVGT1 AVGT1 Nr. internal average

000 1

001 2

010 4

011 8

100 16

101 32

110 64

1 1 1 128

1. Register configuration 7Ah not allowed with ODR = 25Hz/25Hz (Register CTRL_REG1). For ORD

25Hz/25Hz the suggested configuration for RES_CONF is 6Ah.

(1)

Table 17. Pressure resolution

0.020

(1)

Unit

mbar

RES_CONF (hex) RMS noise

70 0.450

71 0.320

72 0.230

73 0.160

74 0.110

75 0.080

76 0.060

77 0.040

78 0.030

79 0.025

(2)

1. Rms noise is calculated as standard deviation of 10 data points.

2. This configuration is not allowed for ODR = 25Hz/25HZ (register CTRL_REG1). For ORD = 25 Hz/ 25 Hz

the suggested configuration for RES_CONF is 6Ah.

Doc ID 022112 Rev 7 19/36

WHO_AM_I Device identification

76543210

10111011

Address: 0Fh

Type: R

Description: This read-only register contains the device identifier that, for LPS331AP, is set to BBh.

CTRL_REG1 Control register 1

76543210

PD ODR2 ODR1 ODR0 DIFF_EN DBDU DELTA_EN SIM

Address: 20h

Type: R/W

Description: Control register.

[7] PD: power down control.

Default value: 0

(0: power-down mode; 1: active mode)

[6:4] ODR2, ODR1, ODR0: output data rate selection.

Default value: 00

(see Ta bl e 1 8 )

[3] DIFF_EN: Interrupt circuit enable.

Default value: 0

(0: interrupt generation disabled; 1: interrupt circuit enabled)

[2] BDU: block data update.

Default value: 0

(0: continuous update; 1: output registers not updated until MSB and LSB reading)

[1] DELTA_EN: delta pressure enable

(1: delta pressure registers enabled. 0: disable)

[0] SIM: SPI Serial Interface Mode selection.

Default value: 0

(0: 4-wire interface; 1: 3-wire interface)

PD bit allows to turn on the device. The device is in power-down mode when PD = ‘0’ (default value after boot). The device is active when PD is set to ‘1’.

ODR2- ODR1 - ODR0 bits allow to change the output data rates of pressure and temperature samples. The default value is “000” which corresponds to “one shot configuration” for both pressure and temperature output. ODR2, ODR1 and ODR0 bits can be configured as described in Ta bl e 1 8.

Note: Before changing the ODR it is necessary to power down the device (CTRL_REG1[7]).

20/36 Doc ID 022112 Rev 7

LPS331AP Register description

Table 18. Output data rate bit configurations

ODR2 ODR1 ODR0 Pressure output data rate

0 0 0 One shot One shot

001 1Hz 1Hz

010 7Hz 1Hz

011 12.5Hz 1Hz

100 25Hz 1Hz

101 7Hz 7Hz

1 1 0 12.5 Hz 12.5 Hz

1 1 1 25 Hz 25 Hz

Temperature output data

rate

DIFF_EN bit is used to enable the circuitry for the computing of differential pressure output.

In default mode (DIF_EN=’0’) the circuitry is turned off. It is suggested to turn on the circuitry only after the configuration of REF_P_x and THS_P_x.

BDU bit is used to inhibit the output registers update between the reading of upper and lower register parts. In default mode (BDU = ‘0’), the lower and upper register parts are updated continuously. If it is not sure to read faster than output data rate, it is recommended to set BDU bit to ‘1’. In this way, after the reading of the lower (upper) register part, the content of that output registers is not updated until the upper (lower) part is read too. This feature avoids reading LSB and MSB related to different samples.

SIM bit selects the SPI serial interface mode. When SIM is ‘0’ (default value) the 4-wire interface mode is selected and data coming from the device are sent to pin #7 (SDO). In 3-wire interface mode, output data are sent to pin #6 (SDI/SDO).

Doc ID 022112 Rev 7 21/36

CTRL_REG2 Control register 2

76543210

BOOT RESERVED SWRESET AUTO_ZERO ONE_SHOT

Address: 21h

Type: R/W

Description: Control register.

[7] BOOT: Reboot memory content. Default value: 0

(0: normal mode; 1: reboot memory content)

[6:3] RESERVED

[2] Software reset. Default value: 0

(0: normal mode; 1: software reset)

[1] Autozero enable. Default value: 0

(0: normal mode; 1: autozero enable)

[0] One shot enable. Default value: 0

(0: waiting for start of conversion; 1: start for a new dataset)

BOOT bit is used to refresh the content of the internal registers stored in the Flash memory block. At the device power-up the content of the Flash memory block is transferred to the internal registers related to trimming functions to permit a good behavior of the device itself. If for any reason, the content of the trimming registers is modified, it is sufficient to use this bit to restore the correct values. When BOOT bit is set to ‘1’ the content of the internal Flash is copied inside the corresponding internal registers and is used to calibrate the device. These values are factory trimmed and they are different for every device. They permit good behavior of the device and normally they should not be changed. At the end of the boot process the BOOT bit is set again to ‘0’.

BOOT bit takes effect after one ODR clock cycle.

SWRESET is the software reset bit. The device is reset to the power on configuration if the SWRESET bit is set to ‘1’ and BOOT is set to ‘1’.

AUTO_ZERO, when set to ‘1’, the actual pressure output is copied in the REF_P_H & REF_P_L & REF_P_XL and kept as reference and the PRESS_OUT_H & PRESS_OUT_L & PRESS _OUT_XL is the difference between this reference and the pressure sensor value.

ONE_SHOT bit is used to start a new conversion when ODR1-ODR0 bits in CTRL_REG1 are set to “000”. In this situation a single acquisition of temperature and pressure is started when ONE_SHOT bit is set to ‘1’. At the end of conversion the new data are available in the output registers, the STAUS_REG[0] and STAUS_REG[1] bits are set to ‘1’ and the ONE_SHOT bit comes back to ‘0’ by hardware.

22/36 Doc ID 022112 Rev 7

LPS331AP Register description

CTRL_REG3 Interrupt control

76543210

INT_H_L PP_OD INT2_S3 INT2_S2 INT2_S1 INT1_S3 INT1_S2 INT1S1

Address: 22h

Type: R/W

Description: Control register.

[7] INT_H_L: Interrupt active high, low. Default value: 0

(0: active high; 1: active low)

[6] PP_OD: Push-pull/open drain selection on interrupt pads. Default value: 0

(0: push-pull; 1: open drain)

[5:3] INT2_S3, INT2_S2, INT2_S1: data signal on INT2 pad control bits. Default value: 00

(see Table 19.)

[2:0 INT1_S3, INT1_S2, INT1_S1: data signal on INT1 pad control bits. Default value: 00

(see Table 19.)

Table 19. Interrupt configurations

INT1(2)_S3 INT1(2)_S2 INT1(2)S1 INT1(2) pin

000 GND

0 0 1 Pressure high (P_high)

0 1 0 Pressure low (P_low)

011P_low OR P_high

100 Data ready

101 Reserved

110 Reserved

111 Tri-state

The device features two fully-programmable interrupt sources (INT1 and INT2) which may be configured to trigger different pressure events. Figure 10 shows the block diagram of the interrupt generation block and output pressure data.

The device may also be configured to generate, through interrupt pins, a Data Ready signal (Drdy) which indicates when a new measured pressure data is available, thus simplifying data synchronization in digital systems.

Doc ID 022112 Rev 7 23/36

Figure 10. Interrupt generation block and output pressure data.

Sensor output pressure

High press int

Low pr ess int

Press Thresh old

Reference Press

Press Thresh old

Reference P ressure

REF_P_H & REF_P_L & REF_P_XL

Pressure T hreshold

THS_P_H & THS_P_L

Positive

Negative

PRESS_OUT_H & PRESS_OUT_L & PRESS_OUT_XL

-1

Low P ress Interrupt

High Press Interrupt

AM08738V1

INTERRUPT_CFG Interrupt configuration

76543210

RESERVED

Address: 23h

LIR PL_E PH_E

Type: R/W

Reset: 00h

Description: Interrupt configuration.

[7:3] RESERVED

[2] LIR: Latch Interrupt request into INT_SOURCE register. Default value: 0.

(0: interrupt request not latched; 1: interrupt request latched)

[1] PL_E: Enable interrupt generation on differential pressure low event. Default value: 0.

(0: disable interrupt request;

1: enable interrupt request on measured differential pressure value lower than preset threshold)

[0] PH_E: Enable interrupt generation on differential pressure high event. Default value: 0

(0: disable interrupt request;

1:enable interrupt request on measured differential pressure value higher than preset

threshold)

24/36 Doc ID 022112 Rev 7

LPS331AP Register description

INT_SOURCE Interrupt source

76543210

00000IAPLPH

Address: 24h

Type: R

Reset: 00h

Description: INT_SOURCE register is cleared by reading INT_ACK register.

[7:3] 0

[2] IA: Interrupt Active.

(0: no interrupt has been generated; 1: one or more interrupt events have been generated).

[1] PL: Differential pressure Low.

(0: no interrupt has been generated; 1: Low differential pressure event has occurred).

[0] PH: Differential pressure High.

(0: no interrupt has been generated; 1: High differential pressure event has occurred).

THS_P_L Threshold pressure (LSB)

76543210

THS7 THS6 THS5 THS4 THS3 THS2 THS1 THS0

Address: 25h

Type: R/W

Reset: 00h

Description: This register contains the low part of threshold value for pressure interrupt

generation. The complete threshold value is given by THS_P_H & THS_P_L and is expressed as unsigned number.

[7:0] THS7 - THS0: Threshold pressure LSB. Default value: 00h.

Doc ID 022112 Rev 7 25/36

THS_P_H Threshold pressure (MSB)

15 14 13 12 11 10 9 8

THS15 THS14 THS13 THS12 THS11 THS10 THS9 THS8

Address: 26h

Type: R/W

Reset: 00h

Description: This register contains the high part of the threshold value for pressure interrupt

generation. The complete threshold value is given by THS_P_H & THS_P_L and is expressed as unsigned number. P_ths(mbar)=(THS_P_H & THS_P_L)[dec]/16.

[15:8] THS7 - THS0: Threshold pressure MSB. Default value: 00h.

STATUS_REG Status register

76543210

0 0 P_OR T_OR 0 0 P_DA T_DA

Address: 27h

Type: R

Reset: 00h

Description: The content of this register is updated every ODR cycle, regardless of BDU value in

CTRL_REG1.

P_DA is set to 1 whenever a new pressure sample is available. P_DA is cleared anytime PRESS_OUT_H (29h) register is read. T_DA is set to 1 whenever a new temperature sample is available. T_DA is cleared anytime TEMP_OUT_H (2Bh) register is read. P_OR bit is set to '1' whenever new pressure data is available and P_DA was set in the previous ODR cycle and not cleared. P_OR is cleared anytime PRESS_OUT_H (29h) register is read. T_OR is set to ‘1’ whenever new temperature data is available and T_DA was set in the previous ODR cycle and not cleared. T_OR is cleared anytime TEMP_OUT_H (2Bh) register is read.

[7:6] 0

[5] P_OR: Pressure data overrun. Default value: 0

(0: no overrun has occurred;

1: new data for pressure has overwritten the previous one)

[4] T_OR: Temperature data overrun. Default value: 0

(0: no overrun has occurred;

1: a new data for temperature has overwritten the previous one)

26/36 Doc ID 022112 Rev 7

LPS331AP Register description

[3:2] 0

[1] P_DA: Pressure data available. Default value: 0

(0: new data for pressure is not yet available;

1: new data for pressure is available)

[0] T_DA: Temperature data available. Default value: 0

(0: new data for temperature is not yet available;

1: new data for temperature is available)

PRESS_OUT_XL Pressure data (LSB)

76543210

POUT7 POUT6 POUT5 POUT4 POUT3 POUT2 POUT1 POUT0

Address: 28h

Type: R

Reset: 00h

Description: Pressure data.

[7:0] POUT7 - POUT0: Pressure data LSB

PRESS_OUT_L Pressure data

15 14 13 12 11 10 9 8

POUT15 POUT14 POUT13 POUT12 POUT11 POUT10 POUT9 POUT8

Address: 29h

Type: R

Reset: 80

Description: Pressure data.

[15:8] POUT15 - POUT8: Pressure data

Doc ID 022112 Rev 7 27/36

PRESS_OUT_H (2Ah) Pressure data (MSB)

24 23 22 21 20 19 18 17

POUT23 POUT22 POUT21 POUT20 POUT19 POUT18 POUT17 POUT16

Address: 2Ah

Type: R

Reset: 2F

Description: Pressure data are expressed as PRESS_OUT_H & PRESS_OUT_L &

PRESS_OUT_XL in 2’s complement. Values exceeding the operating pressure Range (see Table 3) are clipped. Pressure output data: Pout(mbar)=(PRESS_OUT_H & PRESS_OUT_L & PRESS_OUT_XL)[dec]/4096

[24:17] POUT23 - POUT16: Pressure data MSB

28/36 Doc ID 022112 Rev 7

LPS331AP Register description

TEMP_OUT_L (2Bh) Temperature data (LSB)

76543210

TOUT7 TOUT6 TOUT5 TOUT4 TOUT3 TOUT2 TOUT1 TOUT0

Address: 2Bh

Type: R

Reset: 00h

[7:0] TOUT7 - TOUT0: temperature data LSBl

TEMP_OUT_H (2Ch) Temperature data (MSB)

15 14 13 12 11 10 9 8

TOUT15 TOUT14 TOUT13 TOUT12 TOUT11 TOUT10 TOUT9 TOUT8

Address: 2Ch

Type: R

Reset: 00h

[15:8] TOUT15 - TOUT8: temperature data MSB.

Temperature data are expressed as TEMP_OUT_H & TEMP_OUT_L as 2’s complement numbers.

Temperature output data:

T(degC) = 42.5 + (Temp_OUTH & TEMP_OUT_L)[dec]/480

Doc ID 022112 Rev 7 29/36

AMP_CTRL Analog front end control

76543210

RESERVED SELMAIN

Address: 2Dh

Type: R/W

Reset: 00h

[7:1] RESERVED

[0] SELMAIN: Current of operational amplifier selector

‘1’ always high current

‘0’ high current during pressure acquisition and low current during temperature acquisition

DELTA_PRESS_XL (3Ch) Pressure offset

76543210

D ELTA 7 DE LTA 6 D E LTA5 D ELTA 4 DE LTA 3 DE LTA2 D E LTA1 D ELTA 0

Address: 3Ch

Type: R/W

Reset: 00h

[7:0] DELTA0 - DELTA7: Delta pressure register for One Point calibration

DELTA_PRESS_L (3Dh) Pressure offset

15 14 13 12 11 10 9 8

DELTA15 DELTA14 DELTA13 DELTA12 DELTA11 DELTA10 DELTA9 DELTA8

Address: 3Dh

Type: R/W

Reset: 00h

[15:8] DELTA15-DELTA8: Delta pressure register for One Point calibration

30/36 Doc ID 022112 Rev 7

LPS331AP Register description

DELTA_PRESS_L (3Eh) Pressure offset

24 23 22 21 20 19 18 17

DELTA23 DELTA22 DELTA21 DELTA20 DELTA19 DELTA18 DELTA17 DELTA16

Address: 3Eh

Type: R/W

Reset: 00h

[23:16] DELTA23-DELTA16: Delta pressure register for One Point calibration

DELTA_PRESS registers are used to store the one point calibration value to eliminate accuracy shift after soldering. DELTA_PRESS acts on the output pressure when CTRL_REG1[1] DELTA_EN is set to ‘1’.

Doc ID 022112 Rev 7 31/36

Package mechanical section LPS331AP

8 Package mechanical section

In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK specifications, grade definitions and product status are available at: www.st.com. ECOPACK

Figure 11. Package outline for HCLGA-16L (3 x 3 x 1 mm)

packages, depending on their level of environmental compliance. ECOPACK®

is an ST trademark.

32/36 Doc ID 022112 Rev 7

LPS331AP Package mechanical section

Table 20. HCLGA-16L (3 x 3 x 1 mm) mechanical data

Symbol

Min Typ Max

E1 2.850 3.000 3.150

E3 – 0 –

D1 2.850 3.000 3.150

D3 – 0.700 –

R1 – 0.400 –

A1 – 1.000 –

L1 – 1.000 –

N1 – 0.500 –

L2 – 2.000 –

N2 – 1.000 –

P1 – 0.875 –

P2 – 1.275 –

T1 – 0.350 –

Millimeters

T2 – 0.250 –

d – 0.150 –

K – 0.050 –

M – 0.100 –

Figure 12. Tray information

Doc ID 022112 Rev 7 33/36

Package mechanical section LPS331AP

Figure 13. Tape information

34/36 Doc ID 022112 Rev 7

LPS331AP Revision history

9 Revision history

Table 21. Document revision history

Date Revision Changes

12-Aug-2011 1 Initial release.

16-Aug-2011 2

20-Oct-2011 3

15-Dec-2011 4

13-Jan-2012 5

27-Feb-2012 6

29-Mar-2012 7

– Updated order code in Table 1: Device summary – Minor formatting and text modifications throughout the document

– Updated: features list, Ta bl e 3 , Ta bl e 6 , Section 4 and Section 7. – Added: Ta bl e 1 7 , Figure 12 and Figure 13.

– Modified: minor text updates in the Features section, Tab le 3 ,

Ta bl e 4 , Ta bl e 5 , Section 3.1: Sensing element and Figure 11.

Modified: – Temperature range in Ta b le 1 from “-20 to +105” to “-40 to +85”. – Temperature output data in register TEMP_OUT_H (2Ch) from

“42.5” to “22.5”.

– PaccT test condition data in Ta bl e 3 from “P = 260 to 1260 mbar”

to “P = 800 to 1100 mbar”

– Device operating range in Description on page 1 from “

-20 °C to

+105 °C” to “-40 °C to +85 °C”

Document status promoted from preliminary data to datasheet. Modified: – Temperature output data in register TEMP_OUT_H (2Ch) from

“22.5” to “42.5”

– Added register address in register DELTA_PRESS_XL (3Ch) and

modified register address in DELTA_PRESS_L from “3Dh” to “3Eh”.

Modified the description for pin 14 inTa bl e 2 and the list of applications in the cover page.

Doc ID 022112 Rev 7 35/36

LPS331AP

Please Read Carefully:

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36/36 Doc ID 022112 Rev 7

ST LPS331AP User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Table 1. Device summary

1 Block diagram and pin description

1.1 LPS331AP block diagram

Figure 1. LPS331AP block diagram

1.2 Pin description

Figure 2. Pin connection

Table 2. Pin description

2 Mechanical and electrical specifications

2.1 Mechanical characteristics

Table 3. Mechanical characteristics

2.2 Electrical characteristics

Table 4. Electrical characteristics

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

2.3 Absolute maximum ratings

Table 6. Absolute maximum ratings

3 Functionality

3.1 Sensing element

3.2 IC interface

3.3 Factory calibration

4 Application hints

Figure 3. LPS331AP electrical connection

4.1 Soldering information

5 Digital interfaces

5.1 I2C serial interface

Table 7. Serial interface pin description

5.2 I2C serial interface

Table 8. Serial interface pin description

5.2.1 I2C operation

Table 9. SAD+Read/Write patterns

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

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

Table 12. Transfer when master is receiving (reading) one byte of data from slave

5.3 SPI bus interface

Figure 4. Read and write protocol

5.3.1 SPI read

Figure 5. SPI read protocol

Figure 6. Multiple bytes SPI read protocol (2 bytes example)

5.3.2 SPI write

Figure 7. SPI write protocol

Figure 8. Multiple bytes SPI write protocol (2 bytes example)

5.3.3 SPI read in 3-wires mode

Figure 9. SPI read protocol in 3-wires mode

6 Register mapping

Table 14. Registers address map

7 Register description

Table 15. Pressure resolution configuration

Table 16. Temperature resolution configuration

Table 17. Pressure resolution

Table 18. Output data rate bit configurations

Table 19. Interrupt configurations

Figure 10. Interrupt generation block and output pressure data.

8 Package mechanical section

Figure 11. Package outline for HCLGA-16L (3 x 3 x 1 mm)

Table 20. HCLGA-16L (3 x 3 x 1 mm) mechanical data

Figure 12. Tray information

Figure 13. Tape information

9 Revision history

Table 21. Document revision history