ANALOG DEVICES ADXL312 Service Manual

3-Axis, ±1.5 g/±3 g/±6 g/±12 g

VSV

FEATURES

Ultralow power: as low as 57 μA in measurement mode and

0.1 μA in standby mode at V Power consumption scales automatically with bandwidth User-selectable resolution

Fixed 10-bit resolution Full resolution, where resolution increases with g range,

up to 13-bit resolution at ±12 g (maintaining 2.9 mg/LSB scale factor in all g ranges)

Embedded, patent pending FIFO technology minimizes host

processor load

Built-in motion detection functions for activity/inactivity

monitoring Supply and I/O voltage range: 2.0 V to 3.6 V SPI (3- and 4-wire) and I Flexible interrupt modes mappable to either interrupt pin Measurement ranges selectable via serial command Bandwidth selectable via serial command Wide temperature range (−40 to +105°C) 10,000 g shock survival Pb free/RoHS compliant Small and thin: 5 mm × 5 mm × 1.45 mm LFCSP package Qualified for automotive applications

APPLICATIONS

Car alarm Hill start aid (HSA) Electronic parking brake Data recorder (black box)

= 3.3 V (typical)

S

2

C digital interfaces

FUNCTIONAL BLOCK DIAGRAM

Digital Accelerometer

ADXL312

GENERAL DESCRIPTION

The ADXL312 is a small, thin, low power, 3-axis accelerometer with high resolution (13-bit) measurement up to ±12 g. Digital output data is formatted as 16-bit twos complement and is accessible through either a SPI (3- or 4-wire) or I interface.

The ADXL312 is well suited for car alarm or black box applications. It measures the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion or shock. Its high resolution (2.9 mg/LSB) enables resolution of inclination changes of as little as 0.25°. A built-in FIFO facilitates using oversampling techniques to improve resolution to as little as 0.05° of inclination.

Several special sensing functions are provided. Activity and inactivity sensing detects the presence or absence of motion and whether the acceleration on any axis exceeds a user-set level. These functions can be mapped to interrupt output pins. An integrated 32 level FIFO can be used to store data to minimize host processor intervention.

Low power modes enable intelligent motion-based power management with threshold sensing and active acceleration measurement at extremely low power dissipation.

The ADXL312 is supplied in a small, thin 5 mm × 5 mm ×

1.45 mm, 32-lead, LFCSP package.

DD I/O

2

C digital

ADXL312

SENSE

3-AXIS

SENSOR

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

ELECTRONICS

GND

Figure 1. ADXL312 Simplified Block Diagram

ADC

DIGITAL

FILTER

32 LEVEL

FIFO

POWER

MANAGEMENT

CONTROL

AND

INTERRUPT

LOGIC

SERIAL I/O

CS

INT1

INT2

SDA/SDI/SDIO SDO/ALT

ADDRESS SCL/SCLK

08791-001

ADXL312

REVISION HISTORY

Revision 0: Initial Version

Rev. 0 | Page 2 of 32

ADXL312

SPECIFICATIONS

TA = −40°C to +105°C, VS = V

Table 1. Specifications

1

Parameter Conditions Min Typ Max Unit

SENSOR INPUT Each axis

Measurement Range User selectable ±1.5, 3, 6, 12 Nonlinearity Percentage of full scale ±0.5 % Inter-Axis Alignment Error ±0.1 Degrees Cross-Axis Sensitivity2 ±1 %

OUTPUT RESOLUTION Each axis

All g Ranges Default resolution 10 Bits ±1.5 g Range Full resolution enabled 10 Bits ±3 g Range Full resolution enabled 11 Bits ±6 g Range Full resolution enabled 12 Bits ±12 g Range Full resolution enabled 13 Bits

SENSITIVITY Each axis

Scale Factor at X Scale Factor at X Scale Factor at X Scale Factor at X

OUT

, Y , Y , Y , Y

OUT

, Z , Z , Z , Z

Sensitivity at X Sensitivity at X Sensitivity at X Sensitivity at X

OUT

, Y , Y , Y , Y

OUT

, Z , Z , Z , Z

OUT

Sensitivity Change Due to Temperature ±0.01 %/°C

0 g BIAS LEVEL Each axis

Initial 0 g Output T = 25°C, X Initial 0 g Output T = 25°C, Z 0 g Output over Temperature −40°C < T < 105°C, X 0 g Offset Tempco X 0 g Offset Tempco Z

NOISE PERFORMANCE

Noise Density (X-, Y-axes) 200 340 440 μg/√Hz Noise Density (Z-axis) 200 470 595 μg/√Hz

OUTPUT DATA RATE/BANDWIDTH User selectable

Measurement Rate3 6.25 3200 Hz

SELF-TEST4 Data rate ≥ 100 Hz, 2.0 ≤ VS ≤ 3.6

Output Change in X-Axis 0.20 2.10 Output Change in Y-Axis −2.10 −0.20 Output Change in Z-Axis 0.30 3.40

POWER SUPPLY

Operating Voltage Range (VS) 2.0 3.6 V Interface Voltage Range (V Supply Current Data rate > 100 Hz 100 170 300 μA Data rate < 10 Hz 30 55 110 μA Standby Mode Leakage Current 0.1 2 μA Turn-On (Wale-Up) Time5 1.4 ms

TEMPERATURE

Operating Temperature Range −40 +105 °C

= 3.3 V, acceleration = 0 g, unless otherwise noted.

DD I/O

g

±1.5 g, 10-bit or full resolution 2.6 2.9 3.2 mg/LSB

OUT

±3 g, 10-bit resolution 5.2 5.8 6.4 mg/LSB

OUT

±6 g, 10-bit resolution 10.4 11.6 12.8 mg/LSB

OUT

±12 g, 10-bit resolution 20.9 23.2 25.5 mg/LSB

OUT

±1.5 g, 10-bit or full resolution 312 345 385 LSB/g ±3 g, 10-bit resolution 156 172 192 LSB/g ±6 g, 10-bit resolution 78 86 96 LSB/g ±12 g, 10-bit resolution 39 43 48 LSB/g

, Y

−150 +150 mg

OUT

−250 +250 mg

OUT

, Y

, Z

OUT

, Y

±0.8 mg/°C

OUT

±1.5 mg/°C

OUT

−250 +250 mg

OUT

g g g

) 1.7 VS V

DD I/O

Rev. 0 | Page 3 of 32

ADXL312

1

All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed.

2

Cross-axis sensitivity is defined as coupling between any two axes.

3

Bandwidth is half the output data rate.

4

Self-test change is defined as the output (g) when the SELF_TEST bit = 1 (in the DATA_FORMAT register) minus the output (g) when the SELF_TEST bit = 0 (in the

DATA_FORMAT register). Due to device filtering, the output reaches its final value after 4 × τ when enabling or disabling self-test, where τ = 1/(data rate).

5

Turn-on and wake-up times are determined by the user-defined bandwidth. At a 100 Hz data rate, the turn-on and wake-up times are each approximately 11.1 ms. For

other data rates, the turn-on and wake-up times are each approximately τ + 1.1 in milliseconds, where τ = 1/(data rate).

Rev. 0 | Page 4 of 32

ADXL312

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Acceleration

Any Axis, Unpowered 10,000 g

Any Axis, Powered 10,000 g VS −0.3 V to 3.9 V V

−0.3 V to 3.9 V

DD I/O

All Other Pins

Output Short-Circuit Duration

(Any Pin to Ground) Temperature Range

Powered −40°C to +125°C

Storage −40°C to +125°C

−0.3 V to V

3.9 V, whichever is less Indefinite

DD I/O

+ 0.3 V or

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

THERMAL RESISTANCE

θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages.

Table 3. Thermal Resistance

Package Type θJA θ

32-Lead LFCSP Package 27.27 30 °C/W

Unit

JC

ESD CAUTION

Rev. 0 | Page 5 of 32

ADXL312

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

DD I/O

NC

V

NCNCNCNCSCL/SCLK

32313029282726

GND

1

GND GND

NC

V CS

2 3 4 5

S

6 7 8

ADXL312

TOP VIEW

(Not to S cale)

9

10111213141516

NCNCNCNCNCNCNC

RESERVED

NOTES

1. NC = NO CONNECT. DO NOT CONNECT TO T HIS PIN.

2. THE EXPOSED PAD MUST BE SOL DERED TO THE GROUND PL ANE.

Figure 2. Pin Configuration (Top View)

Table 4. Pin Function Descriptions

Pin No. Mnemonic Description

1 GND This pin must be connected to ground. 2 Reserved Reserved. This pin must be connected to VS or left open. 3 GND This pin must be connected to ground. 4 GND This pin must be connected to ground. 5 VS Supply Voltage. 6

CS

Chip Select.

7 Reserved Reserved. This pin must be left open. 8 to19 NC No Connect. Do not connect to this pin. 20 INT1 Interrupt 1 Output. 21 INT2 Interrupt 2 Output. 22 Reserved Reserved. This pin must be connected to GND or left open. 23 SDO/ALT ADDRESS Serial Data Out, Alternate I2C Address Select. 24 SDA/SDI/SDIO Serial Data (I2C), Serial Data In (SPI 4-Wire), Serial Data In/Out (SPI 3-Wire). 25 NC No Connect. Do not connect to this pin. 26 SCL/SCLK Serial Communications Clock. 27 to 30 NC No Connect. Do not connect to this pin. 31 V

Digital Interface Supply Voltage.

DD I/O

32 NC No Connect. EP The exposed pad must be soldered to the ground plane.

NC 25

24 SDA/SDI/SDIO 23

SDO/ALT ADDRESS RESERVED

22

INT2

21 20

INT1

19

NC

18

NC

17 NC

NC

08791-002

Rev. 0 | Page 6 of 32

ADXL312

A

TYPICAL PERFORMANCE CHARACTERISTICS

N>1000 unless otherwise noted.

40

35

30

TION (%)

25

20

15

10

PERCENT OF POPUL

5

0

–150 –120 –60 –30–90 0 6030 90 120 150

Figure 3. X-Axis Zero-g Bias. 25°C, V

35

30

25

TION (%)

20

15

10

PERCENT OF PO P UL

5

ZERO g OFFSET (mg)

S

= V

DD I/O

= 3.3 V

35

30

TION (%)

25

20

15

10

PERCENT OF POPUL

5

0

–3.0

–2.5

–2.0

08791-003

–1.5

ZERO g TEMPERATURE COEFFICIENT (mg/°C)

Figure 6. X-Axis Zero-g Bias Drift, V

40

35

30

TION (%)

25

20

15

10

PERCENT OF POPUL

5

0

0.5

1.0

2.0

3.0

2.5

08791-006

S

= V

DD I/O

1.5

= 3.3 V

–1.0

–0.5

0

–150 –120 –60 –30–90 0 6030 90 120 150

Figure 4. Y Axis Zero-g Bias, 25°C, V

50

45

40

35

TION (%)

30

25

20

15

10

PERCENT OF PO P UL

5

0

–250 –200 –100 –50–150 0 10050 150 200 250

Figure 5. Z Axis Zero-g Bias, 25°C, V

ZERO

g

OFFSET (mg)

g

OFFSET (mg)

S

= V

DD I/O

= 3.3 V

08791-004

08791-005

Rev. 0 | Page 7 of 32

0

–3.0

–2.5

–2.0

–1.5

ZERO g TEMPERATURE COEFFICIENT (mg/°C)

–1.0

Figure 7. Y-Axis Zero-g Bias Drift, V

25

20

TION (%)

15

10

5

PERCENT OF POPUL

0

–3.0

–2.5

–2.0

–1.5

ZERO g TEMPERATURE COEFFICIENT (mg/°C)

–1.0

Figure 8. Z-Axis Zero-g Bias Drift, V

0

0.5

1.0

2.0

–0.5

0

–0.5

1.5

= V

= 3.3 V

S

DD I/O

0.5

1.0

1.5

= V

= 3.3 V

S

DD I/O

3.0

2.5

08791-007

2.0

3.0

2.5

08791-008

ADXL312

A

70

60

50

TION (%)

40

30

20

PERCENT OF POPUL

10

0

312

318

324

Figure 9. X-Axis Sensitivity, V

70

60

50

TION (%)

40

330

336

342

SENSITIVITY (LSB/g)

348

354

360

372

384

378

08791-009

S

= V

= 3.3 V, 25°C

DD I/O

366

30

25

20

TION (%)

15

10

PERCENT OF POPUL

5

0

–0.030

–0.025

–0.020

–0.015

SENSITIVITY TEMPERATURE COEFFICIENT (%/°C)

–0.010

–0.005

0

0.005

0.010

0.015

Figure 12. X-Axis Sensitivity Temperature Coefficient, V

35

30

25

TION (%)

20

S

0.020

= V

0.025

DD I/O

0.030

08791-012

= 3.3 V

30

20

PERCENT OF POPUL

10

0

312

318

324

330

Figure 10. Y-Axis Sensitivity, V

70

60

50

TION (%)

40

30

20

PERCENT OF POPUL

10

0

312

318

324

330

Figure 11. Z-Axis Sensitivity, V

336

342

348

354

SENSITIVITY (LSB/g)

= V

S

DD I/O

336

342

348

354

SENSITIVITY (LSB/g)

= V

S

DD I/O

360

372

366

= 3.3 V, 25°C

360

372

366

= 3.3 V, 25°C

15

10

PERCENT OF POPUL

5

0

384

378

08791-010

–0.030

–0.025

–0.020

–0.015

SENSITIVITY TEMPERATURE COEFFICIENT (%/°C)

Figure 13. Y-Axis Sensitivity Temperature Coefficient, V

35

30

25

TION (%)

20

15

10

PERCENT OF POPUL

5

0

384

378

08791-011

–0.030

–0.025

–0.020

–0.015

SENSITIVITY TEMPERATURE COEFFICIENT (%/°C)

Figure 14. Z-Axis Sensitivity Temperature Coefficient, V

–0.010

–0.005

0

0.005

0.010

0.020

0.015

= V

S

0

0.005

0.010

0.015

= V

S

0.030

0.025

08791-013

= 3.3 V

DD I/O

0.020

0.030

0.025

08791-014

= 3.3 V

DD I/O

Rev. 0 | Page 8 of 32

ADXL312

A

80

70

60

TION (%)

50

40

30

20

PERCENT OF POPUL

10

0

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 SELF-TEST RESPONSE (g)

Figure 15. X-Axis Self-Test Delta, V

70

60

50

TION (%)

40

30

20

PERCENT OF POPUL

10

S

= V

DD I/O

= 3.3 V, 25°C

70

60

TION (%)

50

40

30

20

PERCENT OF POPUL

10

0

08791-015

305070

Figure 18. Standby Mode Current Consumption, V

35

30

25

TION (%)

20

15

10

PERCENT OF POPUL

5

90

110

130 CURRENT (nA)

150

170

190

210

230

S

= V

250

270

= 3.3 V, 25°C

DD I/O

290

310

08791-018

0

–2.1

–1.9

–1.7

–1.5

–1.3

SELF-TEST RESPONSE (g)

Figure 16. Y-Axis Self-Test Delta, V

80

70

60

TION (%)

50

40

30

20

PERCENT OF POPUL

10

0

0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.33.0 SELF-TEST RESPONSE (g)

Figure 17. Z-Axis Self-Test Delta, V

–1.1

= V

S

= V

S

–0.9

DD I/O

–0.7

–0.5

= 3.3 V, 25°C

–0.3

08791-016

08791-017

0

100

120

140

160

180

200

220

240

260

280

CURRENT CONSUMPTION (µA)

300

8791-019

Figure 19. Current Consumption, Measurement Mode, Data Rate = 100 Hz,

V

= V

= 3.3 V, 25°C

S

DD I/O

200

150

100

SUPPLY CURRENT (µA)

50

0

2.0 2.4 2.8 3.2 3.6

SUPPLY VOLTAGE (V)

Figure 20. Supply Current vs. Supply Voltage, V

at 25°C

S

08791-233

Rev. 0 | Page 9 of 32

ADXL312

THEORY OF OPERATION

The ADXL312 is a complete 3-axis acceleration measurement system with a selectable measurement range of ±1.5 g, ±3 g, ±6 g, or ±12 g. It measures both dynamic acceleration resulting from motion or shock and static acceleration, such as gravity, which allows it to be used as a tilt sensor.

The sensor is a polysilicon surface-micromachined structure built on top of a silicon wafer. Polysilicon springs suspend the structure over the surface of the wafer and provide a resistance against acceleration forces.

Deflection of the structure is measured using differential capacitors that consist of independent fixed plates and plates attached to the moving mass. Acceleration deflects the beam and unbalances the differential capacitor, resulting in a sensor output whose amplitude is proportional to acceleration. Phasesensitive demodulation is used to determine the magnitude and polarity of the acceleration.

POWER SEQUENCING

Power can be applied to VS or V damaging the ADXL312. All possible power-on modes are summarized in Tab le 5 . The interface voltage level is set with the interface supply voltage, V ensure that the ADXL312 does not create a conflict on the communication bus. For single-supply operation, V the same as the main supply, V however, V

can differ from VS to accommodate the desired

DD I/O

interface voltage, as long as V After V

is applied, the device enters standby mode, where power

S

consumption is minimized and the device waits for V applied and for the command to enter measurement mode to be received. (This command can be initiated by setting the measure bit in the POWER_CTL register (Address 0x2D).) In addition, any register can be written to or read from to configure the part while the device is in standby mode. It is recommended to configure the device in standby mode and then to enable measurement mode. Clearing the measure bit returns the device to the standby mode.

in any sequence without

DD I/O

, which must be present to

DD I/O

. In a dual-supply application,

S

is greater than or equal to V

S

DD I/O

can be

.

DD I/O

to be

Table 5. Power Sequencing

Condition VS V

Power Off Off Off

Bus Disabled On Off

Bus Enabled Off On

Standby or Measurement

On On

Description

DD I/O

The device is completely off, but there is a potential for a communication bus conflict.

The device is on in standby mode, but communication is unavailable and will create a conflict on the communication bus. The duration of this state should be minimized during power-up to prevent a conflict.

No functions are available, but the device will not create a conflict on the communication bus.

The device is in standby mode, awaiting a command to enter measurement mode, and all sensor functions are off. After the device is instructed to enter measurement mode, all sensor functions are available.

POWER SAVINGS

Power Modes

The ADXL312 automatically modulates its power consumption in proportion to its output data rate, as outlined in Tab le 6 . If additional power savings is desired, a lower power mode is available. In this mode, the internal sampling rate is reduced, allowing for power savings in the 12.5 Hz to 400 Hz data rate range at the expense of slightly greater noise. To enter low power mode, set the LOW_POWER bit (Bit 4) in the BW_RATE register (Address 0x2C). The current consumption in low power mode is shown in Tabl e 7 for cases where there is an advantage to using low power mode. Use of low power mode for a data rate not shown in Tab le 7 does not provide any advantage over the same data rate in normal power mode. Therefore, it is recommended that only data rates shown in Tab le 7 be used in low power mode. The current consumption values shown in Table 6 and Tab le 7 are for a V

of 3.3 V.

S

Rev. 0 | Page 10 of 32

ANALOG DEVICES ADXL312 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

FEATURES

APPLICATIONS

FUNCTIONAL BLOCK DIAGRAM

GENERAL DESCRIPTION

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

THERMAL RESISTANCE

ESD CAUTION

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

TYPICAL PERFORMANCE CHARACTERISTICS

THEORY OF OPERATION

POWER SEQUENCING

POWER SAVINGS

Power Modes