ADXL1004BCPZ-RL7 [ADI]

Low Noise, Wide Bandwidth, MEMS Accelerometer;


型号：	ADXL1004BCPZ-RL7
厂家：	ADI
描述：	Low Noise, Wide Bandwidth, MEMS Accelerometer
文件：	总14页 (文件大小：442K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

Low Noise, Wide Bandwidth,

MEMS Accelerometer

Data Sheet

ADXL1004

FEATURES

FUNCTIONAL BLOCK DIAGRAM

STANDBY

Single, in plane axis accelerometer with analog output

Full-scale range: 500 g

Linear frequency response range: dc to 24 kHz typical

(3 dB point)

ADXL1004

TIMING

GENERATOR

Resonant frequency: 45 kHz typical

Ultralow noise density: 125 µg/√Hz

OUTPUT

MOD

SENSOR

DEMOD

AMP

OUT

AMPLIFIER

Overrange sensing plus dc coupling allows fast recovery time

Complete electromechanical self test

Sensitivity performance

Sensitivity stability over temperature within 5%

Linearity to 0.25% of full-scale range

Cross axis sensitivity: 1.5% (Z-axis acceleration affect on

X-axis; Y-axis acceleration affect on X-axis)

Single-supply operation

OVERRANGE

DETECTION

SELF TEST

Output voltage ratiometric to supply

Low power consumption: 1.0 mA typical

Power saving standby operation mode with fast recovery

RoHS compliant

Figure 1.

−40°C to +125°C operating temperature range

32-lead, 5 mm × 5 mm × 1.80 mm LFCSP package

APPLICATIONS

Condition monitoring

Predictive maintenance

Asset health

Test and measurement

Health usage monitoring systems (HUMSs)

Acoustic emissions

GENERAL DESCRIPTION

The ADXL1004 delivers ultralow noise density over an

extended frequency range and is optimized for bearing fault

detection and diagnostics. The ADXL1004 has typical noise

density of 125 µg/√Hz across the linear frequency range.

Microelectronicmechanical systems (MEMS) accelerometers

have stable and repeatable sensitivity, and are immune to

external shocks up to 10,000 g.

The integrated signal conditioning electronics enable such

features as full electrostatic self test (ST) and an overrange (OR)

indicator, useful for embedded applications. With low power

and single-supply operation of 3.3 V to 5.25 V, the ADXL1004

also enables wireless sensing product design. The ADXL1004 is

available in a 5 mm × 5 mm × 1.80 mm LFCSP package, and

operates over the −40°C to +125°C temperature range.

Rev. 0

Document Feedback

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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

rights of third parties that may result fromits 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 andregisteredtrademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781.329.4700

Technical Support

www.analog.com

ADXL1004

Data Sheet

TABLE OF CONTENTS

Features .............................................................................................. 1

Operating Modes...........................................................................9

Bandwidth ......................................................................................9

Applications Information .............................................................. 10

Application Circuit..................................................................... 10

On Demand Self Test................................................................. 10

Ratiometric Output Voltage...................................................... 10

Interfacing Analog Output Below 10 kHz .............................. 11

Interfacing Analog Output Beyond 10 kHz............................ 12

Overrange.................................................................................... 12

Mechanical Considerations for Mounting.............................. 12

Layout and Design Recommendations ................................... 13

Outline Dimensions....................................................................... 14

Ordering Guide .......................................................................... 14

Applications....................................................................................... 1

Functional Block Diagram .............................................................. 1

General Description......................................................................... 1

Revision History ............................................................................... 2

Specifications..................................................................................... 3

Absolute Maximum Ratings............................................................ 4

Thermal Resistance ...................................................................... 4

Recommended Soldering Profile ............................................... 4

ESD Caution.................................................................................. 4

Pin Configuration and Function Descriptions............................. 5

Typical Performance Characteristics ............................................. 6

Theory of Operation ........................................................................ 9

Mechanical Device Operation .................................................... 9

REVISION HISTORY

1/2018—Revision 0: Initial Version

Rev. 0 | Page 2 of 14

Data Sheet

ADXL1004

SPECIFICATIONS

T_A= 25°C, V_DD= 5.0 V, acceleration = 0 g, unless otherwise noted. All minimum and maximum specifications are guaranteed. Typical

specifications may not be guaranteed.

Table 1.

Parameter

Test Conditions/Comments

Min

500

Typ

Max

Unit

SENSOR

Measurement Range

Nonlinearity¹

Cross Axis Sensitivity²

Percentage of full-scale

Z-axis acceleration affect on X-axis

Y-axis acceleration affect on X-axis

0.25

1.5

SENSITIVITY (RATIOMETRIC TO V_DD)

Sensitivity

mV/g

Sensitivity Change Due to Temperature³

ZERO g OFFSET (RATIOMETRIC TO V_DD)

0 g Output Voltage

T_A= −40°C to +125°C

V_DD/2

0 g Output Range over Temperature⁴

−40°C to +125°C

100 Hz to 20 kHz

NOISE

Noise Density

125

0.1

µg/√Hz

1/f Frequency Corner

FREQUENCY RESPONSE

Sensor Resonant Frequency

5% Bandwidth⁵

kHz

3 dB Bandwidth⁶

SELF TEST

Output Change (Ratiometric to V_DD)

Input Voltage Level

High, V_IH

ST low to ST high

V_DD× 0.7

Low, V_IL

V_DD× 0.3

Input Current

µA

OUTPUT AMPLIFIER

Short-Circuit Current

Output Impedance

Maximum Resistive Load

Maximum Capacitive Load⁷

<0.1

100

Ω

MΩ

No external resistor

With external resistor

POWER SUPPLY (V_DD)

Operating Voltage Range

Quiescent Supply Current

Standby Current

Standby Recovery Time (Standby to Measure Mode)

Turn On Time⁸

3.3

5.0

1.0

225

<50

<550

5.25

1.15

285

µA

µs

°C

Output settled to 1% of final value

OPERATING TEMPERATURE RANGE

−40

+125

¹Nonlinearity is tested using sine vibration at 13 kHz.

²Cross axis sensitivity is defined as the coupling of excitation along a perpendicular axis onto the measured axis output.

³Includes package hysteresis from 25°C.

⁴Difference between the maximum and the minimum values in temperature range.

⁵Specified as a frequency range that is within a deviation range relative to dc sensitivity. The range is limited by an increase in response due to response gain at the

sensor resonant frequency.

⁶Specified as a frequency range that is within a deviation range relative to dc sensitivity. The range is limited by an increase in response due to response gain at the

sensor resonant frequency.

⁷For capacitive loads larger than 100 pF, an external series resistor must be connected (minimum 8 kΩ). The output capacitance must not exceed 22 nF.

⁸Measured time difference from the instant V_DDreaches half its value to the instant at which the output settles to 1% of its final value.

Rev. 0 | Page 3 of 14

ADXL1004

Data Sheet

ABSOLUTE MAXIMUM RATINGS

Table 4. Recommended Soldering Profile

Table 2.

Condition

Parameter

Rating

Profile Feature

Sn63/Pb37

Pb-Free

Acceleration

Average Ramp Rate (T_Lto T_P)

3°C/sec

maximum

3°C/sec

maximum

Any Axis, Powered or Unpowered

Drop Test (Concrete Surface)

V_DD

Output Short-Circuit Duration

(Any Pin to Common Ground)

10,000 g

1.2 m

−0.3 V to +5.5 V

Indefinite

Preheat

Minimum Temperature (T_SMIN

Maximum Temperature (T_SMAX

Time (T_SMINto T_SMAX)(t_S)

)

100°C

150°C

60 sec to

120 sec

150°C

200°C

60 sec to

180 sec

)

Temperature Range (Storage)

−55°C to +150°C

T_SMAXto T_L

Ramp-Up Rate

Stresses at or above those listed under Absolute Maximum

Ratings may cause permanent damage to the product. This is a

stress rating only; functional operation of the product at these

or any other conditions above those indicated in the operational

section of this specification is not implied. Operation beyond

the maximum operating conditions for extended periods may

affect product reliability.

3°C/sec

maximum

3°C/sec

maximum

Time Maintained Above

Liquidous (T_L)

Liquidous Temperature (T_L)

Time (t_L)

183°C

217°C

60 sec to

150 sec

60 sec to

150 sec

Peak Temperature (T_P)

Time Within 5°C of Actual Peak

Temperature (t_P)

240 + 0/−5°C

10 sec to

30 sec

6°C/sec

maximum

260 + 0/−5°C

20 sec to

40 sec

6°C/sec

maximum

THERMAL RESISTANCE

Thermal performance is directly linked to printed circuit board

(PCB) design and operating environment. Careful attention to

PCB thermal design is required.

Ramp-Down Rate

Time 25°C to Peak Temperature

(t25°C)

6 min

maximum

8 min

maximum

_JAis the natural convection junction to ambient thermal

resistance measured in a one cubic foot sealed enclosure.

_JCis the junction to case thermal resistance.

ESD CAUTION

Table 3. Package Characteristics

Package Type

θ_JA

θ_JC

Device Weight

CP-32-26¹

48°C/W

14.1°C/W

<0.2 g

¹Thermal impedance simulated values are based on a JEDEC 2S2P thermal

test board with nine thermal vias. See JEDEC JESD51.

RECOMMENDED SOLDERING PROFILE

Figure 2 and Table 4 provide details about the recommended

soldering profile.

CRITICAL ZONE

t_P

TO T

RAMP-UP

t_L

SMAX

SMIN

t_S

RAMP-DOWN

PREHEAT

t25°C TO PEAK

TIME

Figure 2. Recommended Soldering Profile

Rev. 0 | Page 4 of 14

Data Sheet

ADXL1004

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

NIC

24 DNC

22 DNC

21 DNC

–

DNC

AXIS OF SENSITIVITY

ADXL1004

DNC

TOP VIEW

(Not to Scale)

18 DNC

17 DNC

NOTES

1. NIC = NOT INTERNALLY CONNECTED.

2. DNC = DO NOT CONNECT. LEAVE THIS PIN UNCONNECTED.

3. EXPOSED PAD. THE EXPOSED PAD ON THE BOTTOM OF

THE PACKAGE MUST BE CONNECTED TO GROUND AND

IS REQUIRED FOR BOTH ELECTRICAL AND

MECHANICAL PERFORMANCE.

4. AXIS OF SENSITIVITY IS IN PLANE TO THE PACKAGE

AND HORIZONTAL AS SHOWN.

Figure 3. Pin Configuration

Table 5. Pin Function Descriptions

Pin No.

Mnemonic Description

1 to 9, 31, 32

NIC

Not Internally Connected.

10, 11, 17 to 19, 21 to

26, 29

DNC

Do Not Connect. Leave this pin unconnected.

V_DD

V_SS

3.3 V to 5.25 V Supply Voltage.

Supply Ground.

13, 14, 27, 28

STANDBY

Standby Mode Input, Active High.

Self Test Input, Active High.

Overrange Output. This pin instantaneously indicates when the overrange detection circuit

identifies significant overrange activity. This pin is not latched.

X_OUT

Analog Output Voltage.

EPAD

Exposed Pad. The exposed pad on the bottom of the package must be connected to ground and is

required for both electrical and mechanical performance.

Rev. 0 | Page 5 of 14

ADXL1004

Data Sheet

TYPICAL PERFORMANCE CHARACTERISTICS

100

10k

FREQUENCY (Hz)

100k

3.80 3.84 3.88 3.92 3.96 4.00 4.04 4.08 4.12 4.16 4.20

SENSITIVITY DISTRIBUTION (mV/g)

Figure 4. Frequency Response, High Frequency (>5 kHz) Vibration Response;

a Laser Vibrometer Controller Referencing the ADXL1004 Package Used for

Accuracy

Figure 7. Sensitivity Distribution at 25°C

1000000

DUT 1

10000

1000

100

DUT 2

100000

10000

1000

100

0.01

0.1

FREQUENCY (Hz)

100

10k

FREQUENCY (Hz)

100k

Figure 5. Noise Power Spectral Density (PSD) below 10 Hz vs. Frequency

Figure 8. Noise PSD above 100 Hz

1.0

0.5

–

–0.5

–1.0

–60 –40 –20

100 120 140

100

200

300

400

500

TEMPERATURE (°C)

INPUT ACCELERATION (g)

Figure 6. Sensitivity vs. Temperature

Figure 9. Sensitivity Nonlinearity vs. Input Acceleration

Rev. 0 | Page 6 of 14

Data Sheet

ADXL1004

–2

–4

–6

–8

–10

100

120

2.48

2.49

2.50

2.51

2.52

2.53

TEMPERATURE (°C)

0g OUTPUT DISTRIBUTION (V)

Figure 10. Normalized Offset vs. Temperature

Figure 13. 0 g Offset Histogram at 25°C

1100

1050

1000

950

900

850

800

750

700

650

600

280

260

240

220

200

180

160

140

3.3

3.5

3.7

3.9

4.1

4.3

4.5

4.7

4.9

5.1

5.3

3.3

3.5

3.7

3.9

4.1

4.3

4.5

4.7

4.9

5.1

5.3

SUPPLY VOLTAGE (V)

Figure 14. Standby Current vs. Supply Voltage

Figure 11. Measure Mode Supply Current vs. Supply Voltage

920

940

960

980 1000 1020 1040 1060 1080

212 216 220 224 228 232 236 240 244 248

STANDBY CURRENT (µA)

MEASURE MODE CURRENT (µA)

Figure 12. Measure Mode Current Histogram at 25°C

Figure 15. Standby Current Histogram at 25°C

Rev. 0 | Page 7 of 14

ADXL1004

Data Sheet

2500

2000

1500

1000

500

REFERENCE

DELTA

OVERRANGE

OUT

(V)

STANDBY

–1

–2

6.5

–500

4.0

4.5

5.0

5.5

TIME (ms)

6.0

TIME (µs)

Figure 18. Response to Overload Condition, X_OUTDelta is Difference from

Midscale Voltage

Figure 16. X_OUTOutput Recovery from Standby Mode to Measure Mode

200.5

200.0

199.5

199.0

198.5

198.0

197.5

197.0

196.5

196.0

195.5

204

203

202

201

200

199

198

197

196

195

194

–50

100

150

3.3

3.8

4.3

4.8

5.3

TEMPERATURE (°C)

SUPPLY VOLTAGE (V)

Figure 19. Internal Clock Frequency vs. Supply Voltage at 25°C

Figure 17. Internal Clock Frequency vs. Temperature at 5.0 V Supply Voltage (V_DD

)

Rev. 0 | Page 8 of 14

Data Sheet

ADXL1004

THEORY OF OPERATION

The ADXL1004 is a low noise, single-axis, MEMS accelerometer,

with a 45 kHz resonant frequency that provides an analog output

proportional to mechanical vibration. The ADXL1004 has a high

g range of 500 g, suitable for vibration measurements in high

bandwidth applications. Such applications include vibration

analysis systems for monitoring and diagnosing machines or

system health.

MECHANICAL DEVICE OPERATION

The moving component of 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.

Differential capacitors that consist of independent fixed plates

and plates attached to the moving mass measure the deflection

of the structure. Acceleration deflects the structure and unbalances

the differential capacitor, resulting in a sensor output with amp-

litude proportional to acceleration. Phase sensitive demodulation

determines the magnitude and polarity of the acceleration.

The low noise and high frequency bandwidth allows the

measurement of vibration patterns caused by small moving

components, such as internal bearings. The high g range

provides the dynamic range necessary for in high vibration

environments such as heating, ventilation, and air conditioning

(HVAC) and heavy machine equipment. To achieve proper

performance, be aware of system noise, mounting, and signal

conditioning.

OPERATING MODES

The ADXL1004 has two operating modes: measurement mode

and standby mode. Measurement mode provides a continuous

analog output for active monitoring. Standby mode is a

nonoperational, low power mode.

System noise is affected by supply voltage noise. The analog

output of the ADXL1004 is a ratiometric output; therefore,

supply voltage modulation affects the output. Use a properly

decoupled, stable supply voltage to power the ADXL1004 and to

provide a reference voltage for the digitizing system.

Measurement Mode

Measurement mode is the normal operating mode of the

ADXL1004. In this mode, the accelerometer actively measures

acceleration along the axis of sensitivity and consumes 1.0 mA

(typical) using a 5.0 V supply.

The output signal is impacted by an overrange stimulus. An

overload indicator output feature indicates a condition that is

critical for an intelligent measurement system. For more infor-

mation about the overrange features, see the Overrange section.

Standby Mode

Placing the ADXL1004 in standby mode suspends the measure-

ment with internal reduction of current consumption to 225 µA

(typical for 5.0 V supply). The transition time from standby to

measurement mode is <50 µs. Figure 16 shows the transition

from standby to measure mode.

Proper mounting ensures full mechanical transfer of vibration

to accurately measure the desired vibration rather than vibration

of the measurement system, including the sensor. A common

technique for high frequency mechanical coupling is to use a

sensor stud mount system while considering the mechanical

interface of fixing the ADXL1004 in the stud. For lower frequencies

(below the full capable bandwidth of the sensor), it may be possible

to use magnetic or adhesive mounting. Proper mounting technique

ensures proper and repeatable results that are not influenced by

measurement system mechanical resonances and/or damping at

the desired frequency, and represents an efficient and proper

mechanical transfer to the system being monitored.

BANDWIDTH

The ADXL1004 circuitry supports an output signal bandwidth

beyond the resonant frequency of the sensor, measuring accel-

eration over a bandwidth comparable to the resonant frequency

of the sensor. The output response is a combination of the sensor

response and the output amplifier response. Therefore, external

band limiting or filtering is required; see the Interfacing Analog

Output Below 10 kHz section and the Interfacing Analog

Output Beyond 10 kHz section for more information.

Proper application specific signal conditioning is required to

achieve optimal results. Understanding the measurement

frequency range and managing overload conditions is

important to achieve accurate results. The electrical output

signal of the ADXL1004 requires some band limiting and a

proper digitization bandwidth. See the Interfacing Analog

Output Below 10 kHz section and the Interfacing Analog

Output Beyond 10 kHz section for more information.

When using the ADXL1004 beyond 10 kHz, consider the

nonlinearity due to the resonance frequency of the sensor, the

additional noise due to the wideband output of the amplifier,

and the discrete frequency spurious tone due to coupling of the

internal 200 kHz clock. Aliased interferers in the desired band

cannot be removed, and observed performance degrades. A

combination of high speed sampling and appropriate band

limiting filtering is required for optimal performance.

Rev. 0 | Page 9 of 14

ADXL1004

Data Sheet

APPLICATIONS INFORMATION

4. Subtract the two readings and compare the result to the

expected value from Table 1, while factoring in the

response curve due to supply voltage, if necessary, from

Figure 21.

APPLICATION CIRCUIT

For most applications, a single 1 µF capacitor adequately

decouples the accelerometer from noise on the power supply. A

band limiting filter at the output provides suppression of out of

band noise and signal. A capacitive load between 100 pF and

22 nF is recommended.

The self test function can be activated at any point during

normal operation by setting the ST pin to V_DD. Self test takes

approximately 300 µs from the assertion of the ST pin to a

result. Acceleration outputs return approximately 300 µs after

the release of the ST pin. While performing the self test

measurement, do not use the accelerometer output to measure

external acceleration.

The output amplifier can drive resistive loads up to 2 mA of

source current, for example a load greater than 2.5 kΩ for 5 V

operation. If the output is to drive a capacitive load greater than

or equal to 100 pF, a series resistor of at least 8 kΩ is required to

maintain the amplifier stability.

100

When inactive, the ST and STANDBY pins are forced low. The

overrange indicator is an output that can be monitored to

identify the status of the system.

OPTIONAL

LOW-PASS FILTER

OUT

3.3

3.5

3.7

3.9

4.1

4.3

4.5

4.7

4.9

5.1

5.3

SUPPLY VOLTAGE (V)

Figure 21. Typical Self Test Delta vs. Supply Voltage

ADXL1004

RATIOMETRIC OUTPUT VOLTAGE

The ADXL1004 was tested and specified at V_DD= 5.0 V; however, it

can be powered with V_DDas low as 3.3 V or as high as 5.25 V. Some

performance parameters change as the supply voltage is varied.

The ADXL1004 output is ratiometric to the supply voltage, V_DD

therefore, the output sensitivity (or scale factor) varies propor-

tionally to the supply voltage. At V_DD= 5.0 V, the output sensitivity

is typically 4 mV/g for the ADXL1004. The zero g bias output is

ratiometric also and is nominally midscale relative to the supply

voltage (V_DD/2).

;

(3.3V TO 5.25V

SUPPLY VOLTAGE)

ST (ACTIVE HIGH)

1µF

STANDBY (ACTIVE HIGH)

Figure 20. Application Circuit Change

ON DEMAND SELF TEST

4.5

A fully integrated electromechanical self test function is designed

into the ADXL1004. This function electrostatically actuates the

accelerometer proof mass, resulting in a displacement of the

capacitive sense fingers. This displacement is equivalent to the

displacement that occurs as a result of external acceleration input.

The proof mass displacement is processed by the same signal

processing circuitry as a true acceleration output signal,

providing complete coverage of both the electrical and mechanical

responses of the sensor system.

4.0

3.5

3.0

2.5

2.0

The self test feature can be exercised by the user with the

following steps:

3.0

3.5

4.0

4.5

5.0

1. Measure the output voltage.

2. Turn on self test by setting the ST pin to V_DD

3. Measure the output again.

SUPPLY VOLTAGE (V)

Figure 22. Sensitivity vs. Supply Voltage

Rev. 0 | Page 10 of 14

Data Sheet

ADXL1004

The ADXL1004 output amplifier is stable while driving capacitive

loads up to 100 pF directly without a series resistor. At loads greater

than 100 pF, an 8 kΩ series resistor or greater must be used.

INTERFACING ANALOG OUTPUT BELOW 10 kHz

The ADXL1004 senses mechanical motion along a single axis and

produces a voltage output. The system performance depends on

the output response resulting from sense mechanical vibration and

signal processing of the electrical output.

See Figure 23 for an example of the interface, including compo-

nents when measuring mechanical vibration from 0 kHz to

5 kHz. For a 5 kHz pass band, a single-pole resistor capacitor

(RC) filter is acceptable; however, in some applications, use of a

more aggressive filter and lower sample ADC sample rate is

possible. The following components are recommended to form

a 5 kHz low-pass RC filter at the output of the ADXL1004 when

interfacing to an ADC, such as the ADAQ7980: R1 = 91 kΩ, C1 =

330 pF, R2 = 0 Ω, and C2 = not required. A minimum ADC

sample rate of 16 kHz is recommended to avoid aliasing. When

using sampling rates less than the resonance frequency (typically

45 kHz), be aware and account for the effective gain at the output of

the sensor due to the resonance to ensure out of band signals

are properly attenuated and do not alias in band.

The sensor must be effectively mechanically coupled. Mechanical

coupling can be a complex integration of multiple components,

typically unique for each application. Consideration must be

made for all mechanical interfaces including the mounting of

the MEMS to the PCB (the location on the PCB as well as the

solder chemistry), the size of the PCB (both thickness and active

surface area), and the mounting of the PCB to the system being

monitored (either in a module or directly mounted).

In general, the following guidelines for effective mechanical

interface must be used to support up to 10 kHz bandwidth:

•

Keep the ADXL1004 near a stable mechanical mounting on

the PCB.

See Figure 23 for an example of the interface, including compo-

nents when measuring mechanical vibration from 0 kHz to 10 kHz.

The following components are recommended to form a two-pole

RC filter at the output of the ADXL1004: R1 = 500 Ω, C1 =

10,000 pF, R2 = 1 kΩ, and C2 = 10,000 pF. A minimum ADC

sample rate of 200 kHz is recommended to avoid aliasing.

•

Provide multiple hard mounting points.

Keep the PCB thick and avoid a large surface area PCB that

induces higher magnitude and lower frequency resonances.

Ensure the mechanical connection is sufficiently stiff to

transfer mechanical forces up to the desired frequency.

Below 10 kHz, magnetic and adhesive mounting is possible

with proper attention. The EVAL-ADXL1004Z evaluation

boards can be used as a reference.

•

3.3V TO 5.0V*

AD4000 V

1.8V

0.1µF

(+1µF, OPTIONAL)

The ADXL1004 electrical output supports a bandwidth beyond the

resonance of the sensor. The small signal bandwidth of the output

amplifier in the ADXL1004 is 70 kHz. During the digitization

process, aliasing, which is the folding of higher frequency noise

and signals into the desired band, can occur. To avoid aliasing

noise from the amplifier and other internal circuits (for example,

coupling of the internal 200 kHz clock), it is recommended that

an external filter be implemented at the desired bandwidth and

the chosen analog-to-digital converter (ADC) sampling rate be

faster than the amplifier bandwidth.

10µF

REF

VDD

IN+

OUT

ADAQ7980

IN–

ADXL1004

GND

*3.3V LIMITED BY ADXL1004; 5.0V LIMITED BY AD4000.

Figure 23. Application Circuit for the ADXL1004

The output amplifier is ratiometric to the supply voltage, and

there are two distinct cases regarding digital conversion, as

follows:

•

The user has an ADC downstream of the accelerometer

that can use the V_DDvoltage as a reference. In this case, the

voltage supply tolerance and voltage temperature

coefficient (commonly associated with external regulators)

tracks between the sensor and the ADC. Therefore, the

supply and reference voltage induced error cancels out.

This design approach is recommended.

•

If the ADC cannot reference the same 5 V supply as the

sensor for any reason, the sensitivity of the digitized sensor

output reflects the regulator tolerance and temperature

coefficient.

Rev. 0 | Page 11 of 14

ADXL1004

Data Sheet

The sampling rate must be at least 220 kHz. This sample rate

addresses reducing broadband noise due to the amplifier from

folding back (aliasing) in-band, but does not prevent out of

band signals from aliasing in-band. To prevent out of band

responses, additional external low-pass filtering is required.

INTERFACING ANALOG OUTPUT BEYOND 10 kHz

The ADXL1004 is a high frequency, single-axis MEMS

accelerometer that provides an output signal pass band beyond

the resonance frequency range of the sensor. Although the output

3 dB frequency response bandwidth is approximately 24 kHz

(note that this is a 3 dB response, meaning there is a gain in

sensitivity at this frequency), in some cases, it is desirable to

observe frequency beyond this range. To accommodate this, the

ADXL1004 output amplifier supports a 70 kHz small signal

bandwidth, which is well beyond the resonant frequency of the

sensor.

Another artifact that must be addressed is the coupling of the

internal clock signal at 200 kHz onto the output signal. This

clock spur must be filtered by analog or digital filtering so as

not to affect the analysis of results.

To achieve the lowest rms noise and noise density for extended

bandwidth applications, it is recommended to use at least a

multiple order low-pass filter at the output of the ADXL1004 and

a digitization sample rate of at least 4× the desired bandwidth,

assuming sufficient filtering of the 200 kHz internal clock signal.

Use an ADC sample rate of 1 MSPS or greater along with digital

low-pass filtering to achieve similar performance.

Although a mechanical interface is always important to achieve

accurate and repeatable results in MEMS applications, it is

critical in cases when measuring greater than a few kilohertz.

Typically, magnetic and adhesive mounting are not sufficient to

maintain proper mechanical transfer of vibration through these

frequencies. Mechanical system analysis is required for these

applications.

OVERRANGE

The ADXL1004 has an output (OR pin) to signal when an

overrange event (when acceleration is greater than 2× the full-scale

range) occurs. Built in overrange detection circuitry provides an

alert to indicate a significant overrange event occurred that is

larger than approximately 2× the specified g range. When an

overrange is detected, the internal clock is disabled to the sensor

for 200 µs to maximize protection of the sensor element during an

overrange event. If a sustained overrange event is encountered, the

overrange detection circuitry triggers periodically,

When using the ADXL1004 beyond 10 kHz, consider the

nonlinearity due to the resonance frequency of the sensor, the

additional noise due to the wideband output of the amplifier,

and the discrete frequency spurious tone due to coupling of the

internal 200 kHz clock. If any of these interferers alias in the

desired band, it cannot be removed and observed performance

degrades. A combination of high speed sampling and

appropriate filtering is required for optimal performance.

The first consideration is the effect of the sensor resonance

frequency at 45 kHz. Approaching and above this frequency, the

output response to an input stimulus peaks, as shown in Figure 4.

When frequencies are near or above the resonance, the output

response is outside the linear response range and the sensitivity is

different than observed at lower frequencies. In these frequency

ranges, the relative response (as opposed to absolute value) over

time is typically observed.

approximately every 500 µs (see Figure 18).

MECHANICAL CONSIDERATIONS FOR MOUNTING

Mount the ADXL1004 on the PCB in a location close to a hard

mounting point of the PCB. Mounting the ADXL1004 at an

unsupported PCB location, as shown in Figure 24 may result

in large, apparent measurement errors due to undamped PCB

vibration. Placing the accelerometer near a hard mounting point

ensures that any PCB vibration at the accelerometer is above the

mechanical sensor resonant frequency of the accelerometer and

effectively invisible to the accelerometer. Multiple mounting

points, close to the sensor, and a thicker PCB help reduce the

effect of system resonance on the performance of the sensor.

The ADXL1004 output amplifier small signal bandwidth is

70 kHz. The user must properly interface to the device with

proper signal filtering to avoid issues with out of band noise

aliasing into the desired band. The amplifier frequency response

roll-off can be modeled as a single-pole, low-pass filter, at

70 kHz. In the absence of additional external low-pass filtering,

to avoid aliasing of high frequency noise, choose a sampling

rate of at 2× the equivalent noise bandwidth (ENBW) for a

single-pole, low-pass filter, as follows:

ACCELEROMETERS

PCB

MOUNTING POINTS

ENBW = (π/2) × 70 kHz ≈ 110 kHz

Figure 24. Incorrectly Placed Accelerometers

Rev. 0 | Page 12 of 14

Data Sheet

ADXL1004

LAYOUT AND DESIGN RECOMMENDATIONS

Figure 25 shows the recommended PCB land pattern.

0.03″/0.755mm

0.02″/0.5mm

32 31 30 29 28 27 26 25

0.146″/3.7mm 0.191″/4.855mm

10 11 12 13 14 15 16

0.012″/0.305mm

0.146″/3.7mm

0.191″/4.855mm

Figure 25. Recommended Printed Wiring Board Land Pattern

Rev. 0 | Page 13 of 14

ADXL1004

Data Sheet

OUTLINE DIMENSIONS

DETAIL A

(JEDEC 95)

5.10

5.00 SQ

4.90

0.30

0.25

0.20

PIN 1

INDICATOR

INDIC ATOR AREA OPTIONS

(SEE DETAIL A)

0.50

BSC

3.80

3.70 SQ

3.60

EXPOSED

PAD

0.45

0.40

0.35

0.20 MIN

TOP VIEW

BOTTOM VIEW

3.50 REF

1.85

1.80

1.75

FOR PROPER CONNECTION OF

THE EXPOSED PAD, REFER TO

THE PIN CONFIGURATION AND

FUNCTION DESCRIPTIONS

0.05 MAX

0.02 NOM

COPLANARITY

0.08

SEATING

PLANE

SECTION OF THIS DATA SHEET.

0.203 REF

COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-4

WITH EXCEPTION TO PACKAGE HEIGHT.

Figure 26. 32-Lead Lead Frame Chip Scale Package [LFCSP]

5 mm × 5 mm Body and 1.8 mm Package Height

(CP-32-26)

Dimensions shown in millimeters

ORDERING GUIDE

Model¹

Temperature Range

−40°C to +125°C

g Range

500 g

Package Description

Package Option

CP-32-26

ADXL1004BCPZ

ADXL1004BCPZ-RL

ADXL1004BCPZ-RL7

EVAL-ADXL1004Z

32-Lead Lead Frame Chip Scale Package [LFCSP]

ADXL1004 Evaluation Board

500 g

CP-32-26

¹Z = RoHS Compliant Part.

registered trademarks are the property of their respective owners.

D16508-0-1/18(0)

Rev. 0 | Page 14 of 14

ADXL1004BCPZ-RL7 [ADI]

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