ADXL1002BCPZ-RL [ADI]
Low Noise, High Frequency MEMS Accelerometers;
| 型号： | ADXL1002BCPZ-RL |
| 厂家： | 
ADI |
| 描述： | Low Noise, High Frequency MEMS Accelerometers |
| 文件： | 总14页 (文件大小：752K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Low Noise, High Frequency MEMS
Accelerometers
Data Sheet
ADXL1001/ADXL1002
FEATURES
FUNCTIONAL BLOCK DIAGRAM
V
DD
STANDBY
Single in plane axis accelerometer with analog output
Linear frequency response range from dc to 11 kHz (3 dB point)
Resonant frequency of 21 kHz
ADXL1001/ADXL1002
TIMING
GENERATOR
Ultralow noise density
30 µg/√Hz in 100 g range (ADXL1001)
25 µg/√Hz in 50 g range (ADXL1002)
Overrange sensing plus dc coupling allows fast recovery time
Complete electromechanical self-test
Sensitivity performance
Sensitivity stability over temperature 5%
Linearity to 0.1% of full-scale range
Cross axis sensitivity 1% (ZX), 1% (YX),
Single-supply operation
OUTPUT
MOD
SENSOR
DEMOD
V
OUT
AMP
AMPLIFIER
OVERRANGE
DETECTION
OR
SELF TEST
V
Output voltage ratiometric to supply
Low power consumption 1.0 mA
Power saving standby operation mode with fast recovery
RoHS compliant
ST
SS
Figure 1.
−40°C to +125°C temperature range
5 mm × 5 mm × 1.80 mm LFCSP package
APPLICATIONS
Condition monitoring
Predictive maintenance
Asset health
Test and measurement
Health usage monitoring system (HUMS)
GENERAL DESCRIPTION
The ADXL1001/ADXL1002 deliver ultralow noise density over
an extended frequency range with two full-scale range options,
and are optimized for industrial condition monitoring. The
ADXL1001 ( 100 g) and the ADXL1002 ( 50 g) have typical
noise densities of 30 µg/√Hz and 25 µg/√Hz, respectively. Both
accelerometer devices have stable and repeatable sensitivity,
which is immune to external shocks up to 10,000 g.
The ADXL1001/ADXL1002 have an integrated full electrostatic
self test (ST) function and an overrange (OR) indicator that
allow advanced system level features and are useful for
embedded applications. With low power and single-supply
operation of 3.3 V to 5.25 V, the ADXL1001/ADXL1002 also
enable wireless sensing product design. The ADXL1001/
ADXL1002 are available in a 5 mm × 5 mm × 1.80 mm LFCSP
package, and are rated for operation over a −40°C to +125°C
temperature range.
Rev. 0
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Technical Support
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ADXL1001/ADXL1002
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.............................. 13
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
3/2017—Revision 0: Initial Version
Rev. 0 | Page 2 of 14
Data Sheet
ADXL1001/ADXL1002
SPECIFICATIONS
TA = 25°C, VDD = 5.0 V, acceleration = 0 g, unless otherwise noted.
Table 1.
Test Conditions/
Comments
ADXL1001
Typ
ADXL1002
Typ
Parameter1
SENSOR
Min
Max
Min
Max
Unit
Measurement Range
Linearity
100
0.1
50
0.1
g
%
Percentage of full
scale
ZX cross axis
YX cross axis
Cross Axis Sensitivity2
1.0
1.0
1.0
1.0
%
%
SENSITIVITY (RATIOMETRIC TO VDD
Sensitivity
Sensitivity Change Due to
Temperature3
)
DC
20
5
40
5
mV/g
%
TA = −40°C to +125°C
ZERO g OFFSET (RATIOMETRIC TO VDD
)
0 g Output Voltage
VDD/2
5
VDD/2
5
V
g
0 g Output Range over
−40°C to +125°C
100 Hz to 10 kHz
Temperature4
NOISE
Noise Density
30
25
µg/√Hz
1/f Frequency Corner
FREQUENCY RESPONSE
Sensor Resonant Frequency
5% Bandwidth5
0.1
0.1
Hz
21
4.7
11
21
4.7
11
kHz
kHz
kHz
3 dB Bandwidth5
SELF TEST
Output Change (Ratiometric to VDD
)
ST low to ST high
235
275
510
545
mV
Input Level
High, VIH
VDD × 0.7
VDD × 0.7
V
Low, VIL
VDD × 0.3
VDD × 0.3
V
Input Current
25
25
µA
OUTPUT AMPLIFIER
Short-Circuit Current
Output Impedance
Maximum Resistive Load
Maximum Capacitive Load6
3
<0.1
20
100
22
3
<0.1
20
100
22
mA
Ω
MΩ
pF
nF
No external resistor
With external resistor
POWER SUPPLY ( VDD
)
Operating Voltage Range
Quiescent Supply Current
Standby Current
3.3
5.0
1.0
225
<50
5.25
1.15
285
3.3
5.0
1.0
225
<50
5.25
1.15
285
V
mA
µA
µs
Standby Recovery Time (Standby to Output settled to 1%
Measure Mode)
Turn On Time7
of final value
<550
<550
µs
OPERATING TEMPERATURE RANGE
−40
+125
−40
+125
°C
1 All minimum and maximum specifications are guaranteed. Typical specifications may not be guaranteed.
2 Cross axis sensitivity is defined as the coupling of excitation along a perpendicular axis onto the measured axis output.
3 Includes package hysteresis from 25°C.
4 Difference between maximum and minimum values in temperature range.
5 Specified as frequency range that is within a deviation range relative to dc sensitivity, range is limited by an increase in response due to response gain at the sensor
resonant frequency.
6 For capacitive loads larger than 100 pF, an external series resistor must be connected (minimum 8 kΩ). The output capacitance must not exceed 22 nF.
7 Measured time difference from the instant VDD reaches half its value to the instant at which the output settles to 1% of its final value.
Rev. 0 | Page 3 of 14
ADXL1001/ADXL1002
Data Sheet
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED SOLDERING PROFILE
Table 2.
Figure 2 and Table 4 provide details about the recommended
Parameter
Rating
soldering profile.
Acceleration (Any Axis, Unpowered)
Acceleration (Any Axis, Powered)
Drop Test (Concrete Surface)
VDD
Output Short-Circuit Duration
(Any Pin to Common)
10,000 g
10,000 g
1.2 m
−0.3 V to +5.5 V
Indefinite
CRITICAL ZONE
tP
T
TO T
L
P
T
P
RAMP-UP
T
L
tL
T
SMAX
T
SMIN
Temperature Range (Storage)
−55°C to +150°C
tS
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.
RAMP-DOWN
PREHEAT
t25°C TO PEAK
TIME
Figure 2. Recommended Soldering Profile
Table 4. Recommended Soldering Profile
Condition
THERMAL RESISTANCE
Profile Feature
Sn63/Pb37
Pb-Free
Thermal performance is directly linked to printed circuit board
(PCB) design and operating environment. Careful attention to
PCB thermal design is required.
Average Ramp Rate (TL to TP)
3°C/sec
maximum
3°C/sec
maximum
Preheat
Minimum Temperature (TSMIN
Maximum Temperature (TSMAX
Time, TSMIN to TSMAX (tS)
)
100°C
150°C
60 sec to
120 sec
150°C
200°C
60 sec to
180 sec
θ
JA is the natural convection junction to ambient thermal
)
resistance measured in a one cubic foot sealed enclosure. θJC is
the junction to case thermal resistance.
TSMAX to TL
Ramp-Up Rate
Table 3. Package Characteristics
3°C/sec
3°C/sec
Package Type
CP-32-261
θJA
θJC
Device Weight
maximum
maximum
48°C/W
14.1°C/W
<0.2 g
Time Maintained Above
Liquidous (TL)
Liquidous Temperature (TL)
Time (tL)
1 Thermal impedance simulated values are based on a JEDEC 2S2P thermal
test board with nine thermal vias. See JEDEC JESD51.
183°C
217°C
60 sec to
150 sec
60 sec to
150 sec
Peak Temperature (TP)
240°C +
0°C/−5°C
260°C +
0°C/−5°C
Time Within 5°C of Actual Peak
Temperature (tP)
10 sec to
30 sec
20 sec to
40 sec
Ramp-Down Rate
6°C/sec
6°C/sec
maximum
maximum
Time 25°C to Peak Temperature
(t25°C)
6 min
maximum
8 min
maximum
ESD CAUTION
Rev. 0 | Page 4 of 14
Data Sheet
ADXL1001/ADXL1002
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
NIC
NIC
NIC
NIC
NIC
NIC
NIC
NIC
1
2
3
4
5
6
7
8
24 DNC
23
22 DNC
21 DNC
+
–
DNC
AXIS OF SENSITIVITY
ADXL1001/
20
19
OR
DNC
ADXL1002
TOP VIEW
18 DNC
17 DNC
(Not to Scale)
NOTES
1. NIC = NOT INTERNALLY CONNECTED.
2. DNC = NO NOT CONNECT. LEAVE THIS PIN UNCONNECTED.
3. THE EXPOSED PAD ON THE BOTTOM OF THE PACKAGE MUST BE CONNECTED TO GROUND.
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 unconnected.
12
VDD
VSS
3.3 V to 5.25 V Supply Voltage.
Supply Ground.
13, 14, 27, 28
15
16
20
STANDBY
ST
OR
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.
30
33
VOUT
EPAD
Analog Output Voltage.
Exposed Pad. The exposed pad on the bottom of the package must be connected to ground.
Rev. 0 | Page 5 of 14
ADXL1001/ADXL1002
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
15
10000
1000
100
10
10
5
ADXL1001
ADXL1002
0
–5
–10
1
100
1k
10k
100k
0.01
0.1
1
10
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 4. Frequency Response of ADXL1001/ADXL1002, High Frequency
(>5 kHz) Vibration Response; a Laser Vibrometer Controller Referencing the
ADXL1002 Package Used for Accuracy
Figure 7. ADXL1001/ADXL1002 Noise Power Spectral Density (Noise PSD)
Below 10 Hz
100
90
100
90
80
80
70
70
DEVICE 1
60
DEVICE 1
60
DEVICE 2
DEVICE 2
50
50
DEVICE 3
DEVICE 3
40
30
40
30
20
20
10
10
100
1k
10k
100k
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 8. ADXL1002 Noise Power Spectral Density (PSD)
Figure 5. ADXL1001 Noise Power Spectral Density (PSD) vs. Frequency
5
5
3
3
1
1
–1
–3
–5
–1
–3
–5
–40
–20
0
20
40
60
80
100
120
–40
–10
20
50
80
110
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 6. ADXL1001 Sensitivity vs. Temperature
Figure 9. ADXL1002 Sensitivity vs. Temperature
Rev. 0 | Page 6 of 14
Data Sheet
ADXL1001/ADXL1002
10
10
5
5
0
0
–5
–5
–10
–40
–10
–40
15
70
125
15
70
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 10. ADXL1001 Normalized Offset vs. temperature
Figure 13. ADXL1002 Normalized Offset vs. Temperature
280
260
240
220
200
180
160
140
1100
1050
1000
950
900
850
800
750
700
650
600
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)
SUPPLY VOLTAGE (V)
Figure 11. ADXL1001/ADXL1002 Standby Current vs. Supply Voltage
Figure 14. ADXL1001/ADXL1002 Measure Mode Supply Current vs. Supply
Voltage
60
50
40
30
20
10
40
35
30
25
20
15
10
5
0
0
38.0 38.2 38.4 38.6 38.8 39.0 39.2 39.4 39.6 39.8 40.0
19.0 19.2 19.4 19.6 19.8 20.0 20.2 20.4 20.6 20.8 21.0
ADXL1002 SENSITIVITY (mV)
ADXL1001 SENSITIVITY (mV/g)
Figure 12. ADXL1001 Sensitivity Histogram at 25°C
Figure 15. ADXL1002 Sensitivity Histogram at 25°C
Rev. 0 | Page 7 of 14
ADXL1001/ADXL1002
Data Sheet
40
35
30
25
20
15
10
5
30
25
20
15
10
5
0
0
212 216 220 224 228 232 236 240 244 248
STANDBY CURRENT (µA)
930 945 960 975 990 1005 1020 1035 1050 1065 1080 1095
MEASURE MODE SUPPLY CURRENT (µA)
Figure 16. ADXL1001/ADXL1002 Measure Mode Supply Current Histogram at 5 V
Figure 19. ADXL1001/ADXL1002 Standby Current Histogram at 5 V
0.100
0.075
0.050
0.025
0
0.100
0.750
0.500
0.250
0
–0.250
–0.050
–0.075
–0.100
–0.250
–0.500
–0.750
–0.100
0
20
40
60
80
100
0
10
20
30
40
50
INPUT ACCELERATION (g)
INPUT ACCELERATION (g)
Figure 20. ADXL1002 Sensitivity Nonlinearity vs. Input Acceleration
Figure 17. ADXL1001 Sensitivity Nonlinearity vs. Input Acceleration
40
35
30
25
20
15
10
5
6
V
OUT
5
STANDBY
4
3
2
1
0
0
–1
2.46 2.47 2.48 2.49 2.50 2.51 2.52 2.53 2.54 2.55 2.56 2.57
0
10
30
40
20
TIME (µs)
0g OUTPUT (V)
Figure 18. ADXL1001/ADXL1002 Output (Gray Trace) Settling in Standby
(Black); Output Voltage Settles to Midrail (2.5 V) in Standby in <30 µs;
Effectively Unfiltered (No Low-Pass Filter) Output
Figure 21. ADXL1001/ADXL1002 0 g Output Population
Rev. 0 | Page 8 of 14
Data Sheet
ADXL1001/ADXL1002
THEORY OF OPERATION
The ADXL1001/ADXL1002 are high frequency, low noise single-
axis microelectromechanical systems (MEMS) accelerometers
that provide an analog output that is proportional to mechanical
vibration. The ADXL1001/ADXL1002 have high g ranges of 100 g
and 50 g and are suitable for vibration measurements in high
bandwidth applications such as vibration analysis systems that
monitor and diagnose machine 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.
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 structure
and unbalances the differential capacitor, resulting in a sensor
output with an amplitude 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
parts, such as internal bearings, and the high g range provides
the dynamic range to be used 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 ADXL1001/ADXL1002 have 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 ADXL1001/ADXL1002 is a ratiometric output;
therefore, supply voltage modulation affects the output. Use a
properly decoupled stable supply voltage to power the ADXL1001/
ADXL1002 and to provide a reference voltage for the digitizing
system.
Measurement Mode
Measurement mode is the normal operating mode of the
ADXL1001/ADXL1002. 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 is provided to indicate a
condition that is critical for an intelligent measurement system.
For more information about the overrange features, see the
Overrange section.
Standby
Placing the ADXL1001/ADXL1002 in standby mode suspends
the measurement 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. The transition from
standby to measure mode is shown in Figure 18.
Proper mounting is required to ensure 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 utilize a sensor stud mount system while considering the
mechanical interface of fixing the ADXL1001/ADXL1002 in the
stud. For lower frequencies (below the full capable bandwidth
of the sensor), it is 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 ADXL1001/ADXL1002 circuitry supports an output signal
bandwidth beyond the resonant frequency of the sensor,
measuring acceleration 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 require to
achieve optimal results. An understanding of measurement
frequency range and managing overload condition is important
to achieve accurate results. The electrical output signal of the
ADXL1001/ADXL1002 requires some band limiting and 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 ADXL1001/ADXL1002 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
ADXL1001/ADXL1002
Data Sheet
APPLICATIONS INFORMATION
The self test feature can be exercised by the user with the
following steps:
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.
1. Measure the output voltage.
2. Turn on self test by setting the ST pin to VDD
3. Measure the output again.
.
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 23.
The output amplifier can drive resistive loads up to 2 mA of source
current, for example 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.
The self test function can be activated at any point during
normal operation by setting the ST pin to VDD. Self test takes
approximately 300 µs from the assertion of the ST pin to a
result, and 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.
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
R
700
V
OUT
C
600
V
SS
500
ADXL1002
ADXL1001
400
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
1
2
3
4
5
6
7
8
300
200
100
0
ADXL1001/
ADXL1002
OR
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)
9
10
11
12
13
14
15
16
Figure 23. ADXL1002 Typical Self Test Delta vs. Supply Voltage
V
DD
RATIOMETRIC OUTPUT VOLTAGE
(3.3V TO 5.25V
SUPPLY VOLTAGE)
ST (ACTIVE HIGH)
1µF
The ADXL1001/ADXL1002 are tested and specified at VDD
5.0 V; however, it can be powered with VDD as low as 3.3 V or as
high as 5.25 V. Some performance parameters change as the
supply voltage is varied.
=
STANDBY (ACTIVE HIGH)
Figure 22. ADXL1001/ADXL1002 Application Circuit
ON DEMAND SELF TEST
A fully integrated electromechanical self test function is designed
into the ADXL1001/ADXL1002. 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.
The ADXL1001/ADXL1002 output is ratiometric to the supply
voltage VDD; therefore, the output sensitivity (or scale factor)
varies proportionally to the supply voltage. At VDD = 5.0 V, the
output sensitivity is typically 40 mV/g and 20 mV/g in the
ADXL1002 and ADXL1001, respectively.
The zero g bias output is ratiometric also and is nominally
midscale relative to the supply voltage (VDD/2).
Rev. 0 | Page 10 of 14
Data Sheet
ADXL1001/ADXL1002
45
the desired bandwidth and the chosen ADC sampling rate be
faster than the amplifier bandwidth.
40
35
30
25
The output amplifier is ratiometric to the supply voltage, and
there are two distinct cases regarding digital conversion, as
follows:
•
The user has an analog-to-digital (ADC) downstream of
the accelerometer that can use the VDD voltage 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 and, therefore, the supply and reference voltage
induced error cancels out. This design approach is
recommended.
20
3.3
3.8
4.3
4.8
5.3
SUPPLY VOLTAGE (V)
•
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.
Figure 24. ADXL1002 Sensitivity vs. Supply Voltage
INTERFACING ANALOG OUTPUT BELOW 10 kHz
The ADXL1001/ADXL1002 sense mechanical motion along a
single axis and produces a voltage output. The system
performance depends on the output response that is a result of
mechanical vibration sensed and signal processing of the
electrical output.
The ADXL1001/ADXL1002 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.
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 (location on the PCB as well as 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).
See Figure 25 for an example of the interface including compo-
nents when measuring mechanical vibration from 0 kHz to
5 kHz, using the AD4000 ADC. For a 5 kHz pass band, a single-
pole RC filter is acceptable; however, in some applications, use a
more aggressive filter and lower sample rate. The following
components are recommended to form a two-pole RC filter at
the output of the ADXL1001/ADXL1002: 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.
In general, the following guidelines for effective mechanical
interface must be used to support up to 10 kHz bandwidth:
See Figure 25 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 ADXL1001/ADXL1002:
R1 = 16 kΩ, C1 = 300 pF, R2 = 32 kΩ, and C2 = 300 pF. A
minimum ADC sample rate of 32 kHz is recommended to avoid
aliasing. The two-pole RC filter produces an attenuation of
approximately 84 dB at 200 kHz, the internal clock frequency.
•
Keep the ADXL1001/ADXL1002 near a stable mechanical
mounting on the PCB.
•
•
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-ADXL1001Z and the
EVAL-ADXL1002Z evaluation boards can be used as a
reference.
•
V
DD
3.3V TO 5.0V
1
AD4000 V
1.8V
DD
0.1µF
(+1µF, OPTIONAL)
10µF
V
DD
The ADXL1001/ADXL1002 electrical output supports a bandwidth
beyond the resonance of the sensor. The small signal bandwidth of
the output amplifier in the ADXL1001/ADXL1002 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
R1
R2
REF
VDD
V
IN+
IN–
OUT
C1
C2
AD4000
GND
ADXL1001/
ADXL1002
V
SS
1
3.3V LIMITED BY ADXL1001/ADXL1002; 5.0V LIMITED BY AD4000
Figure 25. Application Circuit for the ADXL1001/ADXL1002
Rev. 0 | Page 11 of 14
ADXL1001/ADXL1002
Data Sheet
That is, 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 ADXL1001/ADXL1002 are high frequency, single-axis
MEMS accelerometer devices that provide an output signal pass
band beyond the resonance frequency range of the sensor.
Although the output 3 dB frequency response bandwidth is
approximately 11 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 accommo-
date this, the ADXL1001/ADXL1002 output amplifier supports
a 70 kHz small signal bandwidth, which is well beyond the
resonant frequency of the sensor.
Another issue 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.
For example, 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
ADXL1001/ADXL1002 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
When using the ADXL1001/ADXL1002 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 ADXL1001/ADXL1002 have an output (OR pin) to signal
when an overrange event (acceleration larger than twice the
full-scale range). Built in overrange detection circuitry provides
an alert to indicate a significant overrange event occurred that is
greater 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, approxi-
mately every 500 µs.
The first consideration is the effect of the sensor resonance
frequency at 21 kHz. Approaching and above this frequency, the
output response to an input stimulus peaks, as shown in Figure 4.
At frequencies near or above the resonance, the output response
is outside the linear response range and, therefore, 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.
200
150
100
50
6
DEVICE UNDER TEST
REFERENCE
OR
4
2
The ADXL1001/ADXL1002 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 least twice the equivalent noise
bandwidth (ENBW) for a single-pole, low-pass filter, as follows:
0
0
–50
–2
–2
–1
0
1
2
3
4
5
6
7
TIME (ms)
Figure 26. ADXL1001/ADXL1002 Behavior During a Continuous Overrange
π
2
ENBW = × 70 kHz ≈110 kHz
Rev. 0 | Page 12 of 14
Data Sheet
ADXL1001/ADXL1002
ACCELEROMETERS
MECHANICAL CONSIDERATIONS FOR MOUNTING
PCB
Mount the ADXL1001/ADXL1002 on the PCB in a location
close to a hard mounting point of the PCB. Mounting the
ADXL1001/ADXL1002 at an unsupported PCB location, as
shown in Figure 27, may result in large, apparent measurement
errors due to undamped PCB vibration. Placing the accel-
erometer near a hard mounting point ensures that any PCB
vibration at the accelerometer is above the mechanical sensor
resonant frequency of the accelerometer and, therefore, effectively
invisible to the accelerometer. Multiple mounting points, close
to the sensor, and a thicker PCB also help to reduce the effect of
system resonance on the performance of the sensor.
MOUNTING POINTS
Figure 27. Incorrectly Placed Accelerometers
LAYOUT AND DESIGN RECOMMENDATIONS
Figure 28 shows the recommended printed circuit board land
pattern.
0.03”/0.755mm
0.02”/0.5mm
32 31 30 29 28 27 26 25
1
2
3
4
5
6
7
8
24
23
22
21
0.146”/3.7mm 0.191”/4.855mm
20
19
18
17
9
10 11 12 13 14 15 16
0.146”/3.7mm
0.012”/0.305mm
0.191”/4.855mm
Figure 28. Recommended Printed Wiring Board Land Pattern
Rev. 0 | Page 13 of 14
ADXL1001/ADXL1002
OUTLINE DIMENSIONS
Data Sheet
DETAIL A
(JEDEC 95)
5.10
5.00 SQ
4.90
0.30
0.25
0.20
PIN 1
PIN 1
INDICATOR
INDIC ATOR AREA OPTIONS
(SEE DETAIL A)
25
32
24
1
0.50
BSC
3.80
3.70 SQ
3.60
EXPOSED
PAD
8
17
16
9
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 29. 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
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
g Range
100 g
100 g
100 g
50 g
Package Description
Package Option
CP-32-26
CP-32-26
ADXL1001BCPZ
32-Lead Lead Frame Chip Scale Package [LFCSP]
32-Lead Lead Frame Chip Scale Package [LFCSP]
32-Lead Lead Frame Chip Scale Package [LFCSP]
32-Lead Lead Frame Chip Scale Package [LFCSP]
32-Lead Lead Frame Chip Scale Package [LFCSP]
32-Lead Lead Frame Chip Scale Package [LFCSP]
ADXL1002 Evaluation Board
ADXL1001BCPZ-RL
ADXL1001BCPZ-RL7
ADXL1002BCPZ
ADXL1002BCPZ-RL
ADXL1002BCPZ-RL7
EVAL-ADXL1002Z
EVAL-ADXL1001Z
CP-32-26
CP-32-26
CP-32-26
CP-32-26
50 g
50 g
ADXL1001 Evaluation Board
1 Z = RoHS Compliant Part.
©2017 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D15431-0-3/17(0)
Rev. 0 | Page 14 of 14
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