ST AIS326DQ User Manual

3-axis, low g accelerometer with digital output

Features

■ 3.3 V single supply operation

■ 1.8 V compatible IOs

■ SPI digital output interface

■ 12 bit resolution

■ Interrupt activated by motion

■ Programmable interrupt threshold

■ Embedded self-test

■ High shock survivability

■ ECOPACK

■ Extended temperature range -40 °C to +105 °C

Applications

■ Anti-theft systems and inertial navigation

■ Motion activated functions

■ Vibration monitoring and compensation

■ Tilt measurements

■ Black boxes, event recorders

Description

The AIS326DQ is a three axes digital output accelerometer that includes a sensing element and an IC interface able to take the information from the sensing element and to provide the measured acceleration signals to the external world through an SPI serial interface. I compatible interface is also available.

compliant

AIS326DQ

MEMS inertial sensor

QFPN-28

process developed by ST to produce inertial sensors and actuators in silicon.

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

The AIS326DQ has a user selectable full scale of ±2 g, ±6 g and it is capable of measuring acceleration over a bandwidth of 640 Hz for all axes. The device bandwidth may be selected accordingly to the application requirements. The self-test capability allows the user to check the functioning of the system.

The device is available in plastic quad flat package no lead surface mount (QFPN) and it is specified over a temperature range extending from -40 °C to +105 °C.

The sensing element, capable of detecting the acceleration, is manufactured using a dedicated

Table 1. Device summary

Order code

AIS326DQ -40 to +105 QFPN-28 Tray

AIS326DQTR -40 to +105 QFPN-28 Tape and reel

June 2010 Doc ID 14956 Rev 4 1/51

Operating temperature

range [° C]

Package Packing

www.st.com

Contents AIS326DQ

Contents

1 Block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.2 QFPN-28 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2 Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . 10

2.1 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.3 Communication interface characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.3.1 SPI - serial peripheral interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.4 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.5 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5.1 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5.2 Zero-g level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5.3 Self test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3 Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.1 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.2 IC interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.3 Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4 Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5 Digital interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.1 SPI bus interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.1.1 SPI Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.1.2 SPI Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.1.3 SPI Read in 3-wires mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

6 Register mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

7 Register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7.1 WHO_AM_I (0Fh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7.2 OFFSET_X (16h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

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AIS326DQ Contents

7.3 OFFSET_Y (17h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7.4 OFFSET_Z (18h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

7.5 GAIN_X (19h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

7.6 GAIN_Y (1Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

7.7 GAIN_Z (1Bh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

7.8 CTRL_REG1 (20h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

7.9 CTRL_REG2 (21h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

7.10 CTRL_REG3 (22h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

7.11 HP_FILTER_RESET (23h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

7.12 STATUS_REG (27h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

7.13 OUTX_L (28h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

7.14 OUTX_H (29h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

7.15 OUTY_L (2Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

7.16 OUTY_H (2Bh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

7.17 OUTZ_L (2Ch) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

7.18 OUTZ_H (2Dh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

7.19 FF_WU_CFG (30h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

7.20 FF_WU_SRC (31h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

7.21 FF_WU_ACK (32h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

7.22 FF_WU_THS_L (34h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

7.23 FF_WU_THS_H (35h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

7.24 FF_WU_DURATION (36h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

7.25 DD_CFG (38h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

7.26 DD_SRC (39h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

7.27 DD_ACK (3Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.28 DD_THSI_L (3Ch) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.29 DD_THSI_H (3Dh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.30 DD_THSE_L (3Eh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.31 DD_THSE_H (3Fh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

8 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

8.1 Mechanical characteristics at 25 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

8.2 Mechanical characteristics at -40 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Doc ID 14956 Rev 4 3/51

Contents AIS326DQ

8.3 Mechanical characteristics at 105 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

8.4 Mechanical characteristics derived from measurement in the -40 °C to +105 °C temperature range 43

8.5 Electro-mechanical characteristics at 25 °C . . . . . . . . . . . . . . . . . . . . . . . 44

8.6 Electrical characteristics at 25 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

8.7 Electrical characteristics at -40 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

8.8 Electrical characteristics at 105 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

9 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

9.1 General guidelines about soldering surface mount accelerometer . . . . . 46

9.2 PCB design guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

9.2.1 PCB design rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

9.3 Stencil design and solder paste application . . . . . . . . . . . . . . . . . . . . . . . 47

9.4 Process consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

10 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

11 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

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AIS326DQ List of tables

List of tables

Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Table 2. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Table 3. Mechanical characteristics @ Vdd = 3.3 V, T = -40 °C to 105 °C unless otherwise noted. . 7

Table 4. Electrical characteristics @ Vdd=3.3 V, T = -40 °C to 105 °C unless otherwise noted . . . . 9

Table 5. SPI slave timing values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 6. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 7. Serial interface pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 8. Registers address map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 9. Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 10. Register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 11. OFFSET_X register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 12. OFFSET_X register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 13. OFFSET_Y register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 14. OFFSET_Y register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 15. OFFSET_Z register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 16. OFFSET_Z register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 17. GAIN_X register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 18. GAIN_X register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 19. GAIN_Y register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 20. GAIN_Y register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 21. GAIN_Z register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 22. GAIN_Z register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 23. CTRL_REG1 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 24. CTRL_REG1 register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 25. CTRL_REG2 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 26. CTRL_REG2 register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 27. CTRL_REG3 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 28. CTRL_REG3 register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 29. STATUS_REG register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 30. STATUS_REG register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 31. OUTX_L register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 32. OUTX_L register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 33. OUTX_H register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 34. OUTX_H register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 35. OUTY_L register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 36. OUTY_L register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 37. OUTY_H register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 38. OUTY_H register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 39. OUTZ_L register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 40. OUTZ_L register description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 41. OUTZ_H register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 42. OUTZ_H register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 43. FF_WU_CFG register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 44. FF_WU_CFG register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 45. FF_WU_SRC register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 46. FF_WU_SRC register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 47. FF_WU_THS_L register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 48. FF_WU_THS_L register description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

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List of tables AIS326DQ

Table 49. FF_WU_THS_H register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 50. FF_WU_THS_H register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 51. FF_WU_DURATION register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 52. FF_WU_DURATION register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 53. DD_CFG register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 54. DD_CFG register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 55. DD_SRC register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Table 56. DD_SRC register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Table 57. DD_THSI_L register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 58. DD_THSI_L register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 59. DD_THSI_H register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 60. DD_THSI_H register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 61. DD_THSE_L register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 62. DD_THSE_L register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 63. DD_THSE_H register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 64. DD_THSE_H register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Table 65. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

6/51 Doc ID 14956 Rev 4

AIS326DQ List of figures

List of figures

Figure 1. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 2. Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 3. SPI slave timing diagram (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 4. AIS326DQ electrical connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 5. Read and write protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 6. SPI read protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 7. Multiple bytes SPI read protocol (2 bytes example) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 8. SPI Write protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 9. Multiple bytes SPI write protocol (2 bytes example) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 10. SPI read protocol in 3-wires mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 11. X-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 12. X-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 13. Y-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 14. Y-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 15. Z-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 16. Z-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 17. X-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 18. X-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 19. Y-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 20. Y-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 21. Z-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 22. Z-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 23. X-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 24. X-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 25. Y-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 26. Y-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 27. Z-axis zero-g level at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 28. Z-axis sensitivity at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 29. X-axis zero-g level change vs. temperature at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 30. X-axis sensitivity change vs. temperature at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 31. Y-axis zero-g level change vs. temperature at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 32. Y-axis sensitivity change vs. temperature at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 33. Z-axis zero-g level change vs. temperature at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 34. Z-axis sensitivity change vs. temperature at 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 35. X and Y axes zero-g level as function of supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Figure 36. X and Y axes sensitivity as function of supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Figure 37. Z axis zero-g level as function of supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Figure 38. Z axis sensitivity as function of supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Figure 39. Current consumption in power-down mode (Vdd=3.3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 40. Current consumption in operational mode (Vdd=3.3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 41. Current consumption in power-down mode (Vdd=3.3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 42. Current consumption in operational mode (Vdd=3.3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 43. Current consumption in power-down mode (Vdd=3.3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 44. Current consumption in operational mode (Vdd=3.3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 45. Recommended land and solder mask design for QFPN packages . . . . . . . . . . . . . . . . . . 43

Figure 46. QFPN-28 mechanical data and package dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Doc ID 14956 Rev 4 7/51

Block diagram and pin description AIS326DQ

1 Block diagram and pin description

1.1 Block diagram

Figure 1. Block diagram

X+

Y+

Z+

MUX

Z-

Y-

X-

REFERENCESELF TEST

CHARGE AMPLIFIER

1.2 QFPN-28 pin description

Figure 2. Pin connection

DIRECTIONS OF THE DETECTABLE ACCELERATIONS

MUX

TRIMMING

CIRCUITS

Reserved

RDY/INT

GND

Vdd

GND

Σ∆

Reconstruction

Filter

Reconstruction

Filter

Reconstruction

Filter

CLOCK

NCNCNC

28 22

CONTROL LOGIC

INTERRUPT GEN.

NCNCNC

Regs Array

AIS326DQ

(TOP VIEW)

814

SDO

SDI/SDO

SPC

Vdd_IO

SPI

Reserved

Vdd

Reserved

GND

SPC

SDO/SDI

SDO

RDY/INT

8/51 Doc ID 14956 Rev 4

AIS326DQ Block diagram and pin description

Table 2. Pin description

Pin# Name Function

1 NC Internally not connected

2 GND 0 V supply

3 Vdd Power supply

4 Reserved Either leave unconnected or connect to GND

5 GND 0 V supply

6 RDY/INT Data ready/inertial wake-up and free-fall interrupt

7, 8 NC Internally not connected

9 SDO SPI serial data output

11 Vdd_IO Power supply for I/O pads

12 SPC SPI serial port clock

13 CS Chip select (logic 0: SPI enabled, logic 1: SPI disabled)

14, 15 NC Internally not connected

16 CK

17 GND 0 V supply

18 Reserved Either leave unconnected or connect to Vdd_IO

19 Vdd Power supply

20 Reserved Connect to Vdd

21 - 28 NC Internally not connected

SDI/

SDO

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

Optional external clock, if not used either leave unconnected or connect to GND

Doc ID 14956 Rev 4 9/51

Mechanical and electrical specifications AIS326DQ

2 Mechanical and electrical specifications

2.1 Mechanical characteristics

Table 3. Mechanical characteristics @ Vdd = 3.3 V, T = -40 °C to 105 °C unless otherwise

Symbol Parameter Test conditions Min. Typ.

FS Measurement range

noted

(1)

(3)

FS bit set to 0 ±1.7 ±2.0

(2)

Max. Unit

FS bit set to 1 ±5.3 ±6.0

Full-scale = ±2 g T = 25 °C, ODR1=40 Hz

Full-scale = ±2 g T = 25 °C, ODR2=160 Hz

1.0

2.0

Dres Device resolution

Full-scale = ±2 g T = 25 °C, ODR3 = 640 Hz

Full-scale = ±2 g T = 25 °C, ODR4 = 2560 Hz

Full-scale = ±2 g 12 bit representation

952 1024 1096

3.9

15.6

So Sensitivity

TCSo

Off

TCOff

Sensitivity change vs temperature

Zero-g level offset accuracy

(5),(6)

Zero-g level change vs temperature

Full-scale = ±6 g 12 bit representation

(4)

Full-scale = ±2 g 12 bit representation

Full-scale = ±2 g X, Y axis

Full-scale = ±2 g Z axis

Full-scale = ±6 g X, Y axis

(4)

Full-scale = ±6 g

(4)

Z axis

Max delta from 25 °C 0.2 mg/

316 340 364

0.025 %/

-100 100

-200 200

-100 100

-200 200

LSb/g

°C

Best fit straight line X, Y axis Full-scale = ±2 g ODR = 40 Hz

Best fit straight line

NL Non linearity

(4)

Z axis Full-scale = ±2 g ODR = 40 Hz

CrAx Cross axis

(4)

10/51 Doc ID 14956 Rev 4

±2

% FS

±3

-5 5 %

AIS326DQ Mechanical and electrical specifications

Table 3. Mechanical characteristics @ Vdd = 3.3 V, T = -40 °C to 105 °C unless otherwise

Symbol Parameter Test conditions Min. Typ.

BW System bandwidth

Self-test output change

Operating temperature range -40 +105 °C

noted

(1)

(continued)

(9)

(7),(8)

Full-scale= ±2 g X axis

Y axis

Full-scale= ±2 g Z axis

Full-scale= ±6 g X axis

Y axis

Full-scale= ±6 g Z axis

(2)

Max. Unit

200 460 750

140 360 580

60 160 260

45 120 200

ODRx/4 Hz

Wh Product weight 0.2 gram

1. The product is factory calibrated at 3.3 V. Operation over 3.6 V is not recommended

2. Typical specifications are not guaranteed

3. Verified by wafer level test and specification of initial offset and sensitivity

4. Guaranteed by design

5. Zero-g level offset value after MSL3 preconditioning

6. Offset can be eliminated by enabling the built-in high pass filter (HPF)

7. Self test output changes with the power supply. “Self-test output change” is defined as OUTPUT[LSb]

CTRL_REG1=1)

8. Output data reach 99% of final value after 5/ODR when enabling Self-test mode due to device filtering

9. ODRx is output data rate. Refer to Table 4 for specifications

- OUTPUT[LSb]

(Self-test bit on CTRL_REG1=0)

. 1LSb = 1g/1024 at 12 bit representation, 2 g Full-scale

(Self-test bit on

LSbFull-scale= ±2 g

LSbFull-scale= ±6 g

Doc ID 14956 Rev 4 11/51

Mechanical and electrical specifications AIS326DQ

2.2 Electrical characteristics

Table 4. Electrical characteristics @ Vdd=3.3 V, T = -40 °C to 105 °C unless otherwise noted

Symbol Parameter Test conditions Min. Typ.

Vdd Supply voltage 3.0 3.3 3.6 V

Vdd_IO I/O pads supply voltage

(3)

1.71 Vdd V

Idd Supply current Vdd = 3.3 V 0.67 0.80 mA

IddPdn

VIH Digital high level Input voltage

VIL Digital low level Input voltage

VOH High level output voltage

VOL Low level output voltage

Current consumption in power-down mode

(3)

0.8*Vdd_IO

0.9*Vdd_IO

ODR1 Output data rate 1 Dec factor = 512 40

ODR2 Output data rate 2 Dec factor = 128 160

ODR3 Output data rate 3 Dec factor = 32 640

ODR4 Output data rate 4 Dec factor = 8 2560

BW System bandwidth

Ton Turn-on time

1. The product is factory calibrated at 3.3 V. Operation over 3.6 V is not recommended

2. Typical specifications are not guaranteed

3. Guaranteed by design

4. Digital filter -3 dB frequency

5. Time to obtain valid data after exiting power-down mode

Operating temperature range -40 +105 °C

(4)

(5)

(2)

Max. Unit

220µA

0.2*Vdd_IO

0.1*Vdd_IO

ODRx/4 Hz

5/ODRx s

(1)

12/51 Doc ID 14956 Rev 4

AIS326DQ Mechanical and electrical specifications

2.3 Communication interface characteristics

2.3.1 SPI - serial peripheral interface

Subject to general operating conditions for Vdd and TOP.

Table 5. SPI slave timing values

(1)

Val ue

Symbol Parameter

Min Max

tc(SPC) SPI clock cycle 125 ns

fc(SPC) SPI clock frequency 8 MHz

tsu(CS) CS setup time 5

th(CS) CS hold time 10

tsu(SI) SDI input setup time 5

Unit

th(SI) SDI input hold time 15

tv(SO) SDO valid output time 55

th(SO) SDO output hold time 7

tdis(SO) SDO output disable time 50

1. Values are guaranteed at 8 MHz clock frequency for SPI with both 4 and 3 wires, based on characterization

results, not tested in production

(2)

h(SI)

v(SO)

(3)

c(SPC)

h(SO)

h(CS)

LSB IN

LSB OUT

(3)

dis(SO)

(3)

Figure 3. SPI slave timing diagram

(3)

su(CS)

SPC

(3)

su(SI)

SDI

SDO

(3)

MSB IN

MSB OUT

2. Measurement points are done at 0.2·Vdd_IO and 0.8·Vdd_IO, for both input and output port

3. When no communication is on-going, data on CS, SPC, SDI and SDO are driven by internal pull-up

resistors

Doc ID 14956 Rev 4 13/51

Mechanical and electrical specifications AIS326DQ

2.4 Absolute maximum ratings

Stresses 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

Vdd_IO I/O pins supply voltage

Input voltage on any control pin (CS, SPC, SDI/SDO, SDO, CK)

Acceleration (any axis, powered, Vdd = 3.3 V)

Acceleration (any axis, unpowered)

Operating temperature range -40 to +105 °C

Storage temperature range -40 to +125 °C

Vin

POW

UNP

STG

ESD Electrostatic discharge protection

(1)

-0.3 to 6.0 V

-0.3 to Vdd +0.1 V

-0.3 to Vdd_IO +0.3 V

3000 g for 0.5 ms

10000 g for 0.1 ms

3000 g for 0.5 ms

10000 g for 0.1 ms

4.0 (HBM) kV

200 (MM) V

1.5 (CDM) kV

1. Supply voltage on any pin should never exceed 6.0 V.

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

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

14/51 Doc ID 14956 Rev 4

AIS326DQ Mechanical and electrical specifications

2.5 Terminology

2.5.1 Sensitivity

Sensitivity describes the gain of the sensor and can be determined e.g. by applying 1 g acceleration to it. As the sensor can measure DC accelerations this can be done easily by pointing the axis of interest towards the center of the earth, noting the output value, rotating the sensor by 180 degrees (point to the sky) and noting the output value again. By doing so, ±1 g acceleration is applied to the sensor. Subtracting the larger output value from the smaller one, and dividing the result by 2, leads to the actual sensitivity of the sensor. This value changes very little over temperature and also very little over time. The Sensitivity tolerance describes the range of sensitivities of a large population of sensors.

2.5.2 Zero-g level

Zero-g level offset (Off) describes the deviation of an actual output signal from the ideal output signal if there is no acceleration present. A sensor in a steady state on a horizontal surface will measure 0 g in X axis and 0 g in Y axis whereas the Z axis will measure 1 g. The output is ideally in the middle of the dynamic range of the sensor (content of OUT registers 00h, 00h with 16 bit representation, data expressed as 2’s complement number). A deviation from ideal value in this case is called Zero-g offset. Offset is to some extent a result of stress to a precise MEMS sensor and therefore the offset can slightly change after mounting the sensor onto a printed circuit board or exposing it to extensive mechanical stress. Offset changes little over temperature, see “Zero-g level change vs. temperature”. The Zero-g level of an individual sensor is stable over lifetime. The Zero-g level tolerance describes the range of Zero-g levels of a population of sensors.

2.5.3 Self test

Self test allows to test the mechanical and electric part of the sensor, allowing the seismic mass to be moved by means of an electrostatic test-force. The self-test function is off when the self-test bit of CTRL_REG1 (control register 1) is programmed to ‘0‘. When the self-test bit of CTRL_REG1 is programmed to ‘1‘an actuation force is applied to the sensor, simulating a definite input acceleration. In this case the sensor outputs will exhibit a change in their DC levels which is related to the selected full scale and depending on the Supply Voltage through the device sensitivity. When Self Test is activated, the device output level is given by the algebraic sum of the signals produced by the acceleration acting on the sensor and by the electrostatic test-force. If the output signals change within the amplitude specified inside Table 3 or 4 then the sensor is working properly and the parameters of the interface chip are within the defined specification.

Doc ID 14956 Rev 4 15/51

Functionality AIS326DQ

3 Functionality

The AIS326DQ is a high performance, low-power, digital output 3-axes linear accelerometer packaged in a QFN package. The complete device includes a sensing element and an IC interface able to take the information from the sensing element and to provide a signal to the external world through an SPI serial interface.

3.1 Sensing element

A proprietary process is used to create a surface micro-machined accelerometer. The technology allows to carry out suspended silicon structures which are attached to the substrate in a few points called anchors and are free to move in the direction of the sensed acceleration. To be compatible with the traditional packaging techniques a cap is placed on top of the sensing element to avoid blocking the moving parts during the moulding phase of the plastic encapsulation.

When an acceleration is applied to the sensor the proof mass displaces from its nominal position, causing an imbalance in the capacitive half-bridge. This imbalance is measured using charge integration in response to a voltage pulse applied to the sense capacitor.

At steady state the nominal value of the capacitors are few pF and when an acceleration is applied the maximum variation of the capacitive load is up to 100 pF.

3.2 IC interface

The complete measurement chain is composed by a low-noise capacitive amplifier which converts into an analog voltage the capacitive unbalancing of the MEMS sensor and by three Σ∆ analog-to-digital converters, one for each axis, that translate the produced signal into a digital bitstream.

The Σ∆ converters are coupled with dedicated reconstruction filters which remove the high frequency components of the quantization noise and provide low rate and high resolution digital words.

The charge amplifier and the Σ∆ converters are operated respectively at 61.5 kHz and 20.5 kHz.

The data rate at the output of the reconstruction depends on the user selected decimation factor (DF) and spans from 40 Hz to 2560 Hz.

The acceleration data may be accessed through an SPI interface thus making the device particularly suitable for direct interfacing with a microcontroller.

The AIS326DQ features a data-ready signal (RDY) which indicates when a new set of measured acceleration data is available thus simplifying data synchronization in digital system employing the device itself.

The AIS326DQ may also be configured to generate an inertial wake-up, direction detection and free-fall interrupt signal accordingly to a programmed acceleration event along the enabled axes.

16/51 Doc ID 14956 Rev 4

+ 35 hidden pages