Low Noise, Wide Bandwidth,
MEMS Accelerometer
Data Sheet ADXL1005
Rev. 0 Document Feedback
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FEATURES
Single, in plane axis accelerometer with analog output
Full-scale range: ±100 g
Linear frequency response range: dc to 23 kHz typical
(3 dB point)
Resonant frequency: 42 kHz typical
Ultralow noise density: 75 μg/√Hz
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 effect on
x-axis, y-axis acceleration effect on x-axis)
Single-supply operation
Output voltage ratiometric to supply
Low power consumption: 1.0 mA typical
Power saving standby operation mode with fast recovery
RoHS compliant
−40°C to +125°C operating temperature range
32-lead, 5 mm × 5 mm × 1.8 mm LFCSP package
APPLICATIONS
Condition monitoring
Predictive maintenance
Asset health
Test and measurement
Health usage monitoring systems (HUMSs)
Acoustic emissions
FUNCTIONAL BLOCK DIAGRAM
TIMING
GENERATOR
ADXL1005
X
OUT
OR
SENSOR
MOD AMP
SELF TEST
ST V
SS
OUTPUT
AMPLIFIER
DEMOD
OVERRANGE
DETECTION
V
DD
STANDBY
16589-001
Figure 1.
GENERAL DESCRIPTION
The ADXL1005 delivers ultralow noise density over an
extended frequency range and is optimized for bearing fault
detection and diagnostics. The ADXL1005 has a typical noise
density of 75 μg/√Hz across the linear frequency range.
Microelectronicmechanical systems (MEMS) accelerometers
have stable and repeatable sensitivity, and are immune to
external shocks of 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 3.0 V to 5.25 V, the ADXL1005
also enables wireless sensing product design. The ADXL1005 is
available in a 5 mm × 5 mm × 1.8 mm LFCSP package, and
operates over the −40°C to +125°C temperature range.
ADXL1005 Data Sheet
Rev. 0 | Page 2 of 14
TABLE OF CONTENTS
Features .............................................................................................. 1
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
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
REVISION HISTORY
4/2018—Revision 0: Initial Version
Data Sheet ADXL1005
Rev. 0 | Page 3 of 14
SPECIFICATIONS
TA = 25°C, VDD = 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 Typ Max Unit
SENSOR
Measurement Range ±100 g
Linearity1 Percentage of full-scale ±0.25 %
Cross Axis Sensitivity2 Z-axis acceleration effect on x-axis ±0.7 %
Y-axis acceleration effect on x-axis ±1.5 %
SENSITIVITY (RATIOMETRIC TO VDD)
Sensitivity DC 20 mV/g
Sensitivity Change Due to Temperature3 T
A = −40°C to +125°C ±5 %
ZERO g OFFSET (RATIOMETRIC TO VDD)
0 g Output Voltage VDD/2 V
0 g Output Range over Temperature4 −40°C to +125°C 9 g
NOISE
Noise Density 100 Hz to 20 kHz 75 μg/√Hz
100 Hz to 20 kHz, at 3.0 V supply 125 μg/√Hz
1/f Frequency Corner 0.1 Hz
FREQUENCY RESPONSE
Sensor Resonant Frequency 37.7 42 kHz
5% Bandwidth5 9 kHz
3 dB Bandwidth6 23 kHz
SELF TEST
Output Change (Ratiometric to VDD) ST low to ST high 420 490 mV
Input Voltage Level
High, VIH V
DD × 0.7 V
Low, VIL V
DD × 0.3 V
Input Current 25 μA
OUTPUT AMPLIFIER
Short-Circuit Current 3 mA
Output Impedance <0.1 Ω
Maximum Resistive Load 20
Maximum Capacitive Load7 No external resistor 100 pF
With external resistor 22 nF
POWER SUPPLY (VDD)
Operating Voltage Range 3.0 5.0 5.25 V
Quiescent Supply Current 1.0 1.15 mA
Standby Current 225 285 μA
Standby Recovery Time (Standby to Measure Mode) Output settled to 1% of final value <50 μs
Turn On Time8 <550 μs
OPERATING TEMPERATURE RANGE −40 +125 °C
1 Linearity is tested using sine vibration at 100 Hz.
2 Cross axis sensitivity is defined as the coupling of excitation along a perpendicular axis onto the measured axis output. Guaranteed by characterization.
3 Includes package hysteresis from 25°C.
4 Difference between the maximum and the minimum values in temperature range.
5 Specified 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.
6 Specified 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.
7 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.
8 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.
ADXL1005 Data Sheet
Rev. 0 | Page 4 of 14
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Acceleration
Mechanical Shock: Any Axis, Powered
or Unpowered per IEC 60068-2-27
10,000 g
Drop Test (Concrete Surface), per
AEC-Q100 Test G5
1.2 m
VDD −0.3 V to +5.5 V
Output Short-Circuit Duration
(Any Pin to Common Ground)
Indefinite
Temperature Range (Storage) −55°C to +150°C
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.
THERMAL RESISTANCE
Thermal performance is directly linked to printed circuit board
(PCB) design and operating environment. Careful attention to
PCB thermal design is required.
θJA 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.
Table 3. Package Characteristics
Package Type θJA θ
JC Device Weight
CP-32-261 48°C/W 14.1°C/W <0.2 g
1 Thermal 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.
t
P
t
L
t25°C TO PEAK
t
S
PREHEAT
CRITICAL ZONE
T
L
TO T
P
TEMPERATURE
TIME
RAMP-DOWN
RAMP-UP
T
SMIN
T
SMAX
T
P
T
L
16589-002
Figure 2. Recommended Soldering Profile
Table 4. Recommended Soldering Profile
Profile Feature
Condition
Sn63/Pb37 Pb-Free
Average Ramp Rate (TL to TP) 3°C/sec
maximum
3°C/sec
maximum
Preheat
Minimum Temperature (TSMIN) 100°C 150°C
Maximum Temperature (TSMAX) 150°C 200°C
Time (TSMIN to TSMAX)(tS) 60 sec to
120 sec
60 sec to
180 sec
TSMAX to TL
Ramp-Up Rate 3°C/sec
maximum
3°C/sec
maximum
Time Maintained Above
Liquidous (TL)
Liquidous Temperature (TL) 183°C 217°C
Time (tL) 60 sec to
150 sec
60 sec to
150 sec
Peak Temperature (TP) 240 + 0/−5°C 260 + 0/−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
maximum
6°C/sec
maximum
Time 25°C to Peak Temperature
(t25°C)
6 min
maximum
8 min
maximum
ESD CAUTION
Data Sheet ADXL1005
Rev. 0 | Page 5 of 14
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
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.
24 DNC
23 DNC
22 DNC
21 DNC
20 OR
19 DNC
18 DNC
17 DNC
1
2
3
4
5
6
7
8
NIC
NIC
NIC
NIC
NIC
NIC
NIC
NIC
9
10
11
12
13
14
15
16
NIC
DNC
DNC
V
DD
V
SS
V
SS
STANDBY
ST
32
31
30
29
28
27
26
25
NIC
NIC
X
OUT
DNC
V
SS
V
SS
DNC
DNC
ADXL1005
TOP VIEW
(Not to Scale)
+–
16589-003
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.
12 VDD 3.0 V to 5.25 V Supply Voltage.
13, 14, 27, 28 VSS Supply Ground.
15 STANDBY Standby Mode Input, Active High.
16 ST Self Test Input, Active High.
20 OR
Overrange Output. This pin instantaneously indicates when the overrange detection circuit
identifies significant overrange activity. This pin is not latched.
30 XOUT 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.
ADXL1005 Data Sheet
Rev. 0 | Page 6 of 14
TYPICAL PERFORMANCE CHARACTERISTICS
10 1k 10k 100k
NORMALIZED AMPLITUDE
(OUTPUT (g)/REFERENCE (g))
FREQUENCY (Hz)
16589-004
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
100
Figure 4. Frequency Response, High Frequency (>5 kHz) Vibration Response;
a Laser Vibrometer Controller Referencing the ADXL1005 Package Used for
Accuracy
1
10
100
1000
10000
100000
0.01 0.1 1 10
NOISE POWER SPECTRAL DENSITY (µg/Hz)
FREQUENCY (Hz)
DUT 1
DUT 2
16589-006
Figure 5. Noise Power Spectral Density (PSD) Below 10 Hz vs. Frequency
40 20 0 20 40 60 80 100 120
–5.0
–2.5
0
2.5
5.0
SENSITIVITY (%)
TEMPERATURE (°C)
16589-025
Figure 6. Sensitivity vs. Temperature
0
5
10
15
20
25
30
40
50
35
45
19.0 19.2 19.4 19.6 19.8 20.0 20.2 20.4 20.6 20.8 21.0
PERCENT OF POPUL
A
TION (%)
SENSITIVITY DISTRIBUTION (mV/g)
16589-014
Figure 7. Sensitivity Distribution at 25°C
10
100
1000
100 1k 10k 100k
NOISE PSD (µg/Hz)
FREQUENCY (Hz)
16589-005
Figure 8. Noise PSD Above 100 Hz
0204060
80 120100
SENSITIVITY NONLINEARITY (% of Full Scale)
INPUT ACCELERATION (g)
16589-009
–0.5
–0.4
–0.3
–0.2
–0.1
0
0.1
0.2
0.3
0.4
0.5
Figure 9. Sensitivity Nonlinearity vs. Input Acceleration
Data Sheet ADXL1005
Rev. 0 | Page 7 of 14
–10
–8
–6
–4
–2
0
2
4
6
8
10
40 20 0 20 40 60 80 100 120
NORMALIZED OFFSET (g)
TEMPERATURE (°C)
16589-024
Figure 10. Normalized Offset vs. Temperature
1100
1050
1000
950
900
850
800
750
700
650
600
SUPPLY VOLTAGE (V)
MEASURE MODE SUPPLY CURRENTA)
16589-022
3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2
Figure 11. Measure Mode Supply Current vs. Supply Voltage
0
5
10
15
20
25
30
35
40
PERCENT OF POPUL
A
TION (%)
920 940 960 980 1000 1020 1040 1060 11001080
MEASURE MODE CURRENTA)
16589-016
Figure 12. Measure Mode Current Histogram at 25°C
0
5
10
15
20
25
30
35
PERCENT OF POPULATION (%)
2.48 2.49 2.50 2.51 2.52 2.53
0g OUTPUT DISTRIBUTION (V)
16589-017
Figure 13. 0 g Offset Histogram at 25°C
140
160
180
200
220
STANDBY CURRENT (µA)
240
260
280
16589-023
SUPPLY VOLTAGE (V)
3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2
Figure 14. Standby Current vs. Supply Voltage
0
5
10
15
20
25
30
35
212 216 220 224 228 232 236 240 244 248
PERCENT OF POPUL
A
TION (%)
STANDBY CURRENTA)
16589-015
Figure 15. Standby Current Histogram at 25°C
ADXL1005 Data Sheet
Rev. 0 | Page 8 of 14
–2
–1
0
1
2
3
4
5
6
0 5 10 15 20 25 30 35 40
V
O
L
T
AGE (V)
TIME (µs)
STANDBY
XOUT
16589-026
Figure 16. XOUT Output Recovery from Standby Mode to Measure Mode
TEMPERATURE (°C)
–50 0 50 100 150
INTERNAL CLOCK FREQUENCY,
V
DD
= 5.0V (kHz)
16589-019
180
185
190
195
200
205
210
215
220
Figure 17. Internal Clock Frequency vs. Temperature at 5.0 V Supply Voltage (VDD)
–1
0
1
2
3
OUTPUT (V)
4
5
6
–100
–50
0
100
50
150
200
250
300
–5 0 5 10
ACCELERATION (g)
TIME (ms)
REFERENCE (g)
X
OUT
(g)
OR OUTPUT (V)
16589-008
Figure 18. Response to Overload Condition, XOUT Delta is Difference from
Midscale Voltage
190
193
194
196
198
200
202
204
206
208
210
3.0 3.5 4.0 4.5 5.0
INTERN
A
L CLOCK FREQUENCY (kHz)
SUPPLY VOLTAGE (V)
16589-020
Figure 19. Internal Clock Frequency vs. Supply Voltage at 25°C
Data Sheet ADXL1005
Rev. 0 | Page 9 of 14
THEORY OF OPERATION
The ADXL1005 is a low noise, single-axis, MEMS accelerometer,
with a 42 kHz resonant frequency that provides an analog output
proportional to mechanical vibration. The ADXL1005 has a high
g range of ±100 g, suitable for vibration measurements in high
bandwidth applications. Such applications include vibration
analysis systems for monitoring and diagnosing machines or
system health.
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 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.
System noise is affected by supply voltage noise. The analog
output of the ADXL1005 is a ratiometric output. Therefore,
supply voltage modulation affects the output. Use a properly
decoupled, stable supply voltage to power the ADXL1005 and to
provide a reference voltage for the digitizing system.
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.
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 ADXL1005 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.
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 ADXL1005 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.
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.
OPERATING MODES
The ADXL1005 has two operating modes: measure mode and
standby mode. Measure mode provides a continuous analog
output for active monitoring. Standby mode is a nonoperational,
low power mode.
Measure Mode
Measure mode is the normal operating mode of the ADXL1005.
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.
Standby Mode
Placing the ADXL1005 in standby mode suspends the measure-
ment and reduces the internal current consumption to 225 μA
(typical for the 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.
BANDWIDTH
The ADXL1005 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.
When using the ADXL1005 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.
ADXL1005 Data Sheet
Rev. 0 | Page 10 of 14
APPLICATIONS INFORMATION
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 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.
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.
24
23
22
21
20
19
18
17
1
2
3
4
5
6
7
8
V
DD
(3.0V TO 5.25V
S
UPPLY VOLTAGE)
STANDBY (ACTIVE HIGH)
ST (ACTIVE HIGH)
V
OUT
R
1µF
C
V
SS
ADXL1005
32 31 30 29 26 25
9 10111213141516
28 27
OR
OPTIONAL
LOW-PASS FILTER
16589-007
Figure 20. Application Circuit
ON DEMAND SELF TEST
A fully integrated electromechanical self test function is designed
into the ADXL1005. 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 self test feature can be exercised by the user with the
following steps:
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 21.
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. 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.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.25.0
SELF TEST DEL
T
A
(mV)
SUPPLY VOLTAGE (V)
16589-021
MAXIMUM
TYPICAL
MINIMUM
Figure 21. Typical Self Test Delta vs. Supply Voltage
RATIOMETRIC OUTPUT VOLTAGE
The ADXL1005 was tested and specified at VDD = 5.0 V. However,
the ADXL1005 can be powered with VDD as low as 3.0 V or as high
as 5.25 V. Some performance parameters change as the supply
voltage is varied.
The ADXL1005 output is ratiometric to the supply voltage, VDD.
Therefore, the output sensitivity (or scale factor) varies propor-
tionally to the supply voltage. At VDD = 5.0 V, the output sensitivity
is typically 20 mV/g for the ADXL1005. The zero g bias output
is ratiometric also and is nominally midscale relative to the
supply voltage (VDD/2).
10
12
14
16
20
18
22
3.0 3.5 4.0 4.5 5.0
SENSITIVITY (mV/g)
SUPPLY VOLTAGE (V)
16589-122
Figure 22. Sensitivity vs. Supply Voltage
Data Sheet ADXL1005
Rev. 0 | Page 11 of 14
INTERFACING ANALOG OUTPUT BELOW 10 kHz
The ADXL1005 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.
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 ADXL1005 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-ADXL1005Z evaluation
boards can be used as a reference.
The ADXL1005 electrical output supports a bandwidth beyond the
resonance of the sensor. The small signal bandwidth of the output
amplifier in the ADXL1005 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.
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 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. 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.
The ADXL1005 output amplifier is stable while driving capacitive
loads of up to 100 pF directly without a series resistor. At loads
greater than 100 pF, an 8 kΩ or greater series resistor must be used.
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 ADXL1005 when
interfacing to an ADC, such as the ADAQ7980: R1 = 91 kΩ, C1 =
330 pF, R2 = 0 Ω, and C2 is 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
42 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 into the band.
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 ADXL1005: 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.
REF
GND
IN+
X
OUT
IN
VDD
V
DD
V
SS
ADAQ7980 V
DD
ADAQ7980
V
DD
3.0V TO 5.1V*
*
3.0V LIMITED BY ADXL1005; 5.1V LIMITED BY ADAQ7980.
0.1µF
+1µF, OPTIONAL)
10µF
R1
C1
R2
C2
ADXL1005
16589-010
Figure 23. Application Circuit for the ADXL1005
ADXL1005 Data Sheet
Rev. 0 | Page 12 of 14
INTERFACING ANALOG OUTPUT BEYOND 10 kHz
The ADXL1005 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 21 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
frequency, the ADXL1005 output amplifier supports a 70 kHz
small signal bandwidth, which is well beyond the resonant
frequency of the sensor.
Although a mechanical interface is always important to achieve
accurate and repeatable results in MEMS applications, it is critical
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.
When using the ADXL1005 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, the aliasing 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 42 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.
The ADXL1005 output amplifier small signal bandwidth is
70 kHz. The user must 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 2× the equivalent
noise bandwidth (ENBW) for a single-pole, low-pass filter, as
follows:
ENBW = (π/2) × 70 kHz ≈ 110 kHz
The sample rate must be at least 220 kHz. This sample rate
reduces 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.
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 ADXL1005 and
a digitization sample rate of at least 4× the desired bandwidth,
assuming there is 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.
OVERRANGE
The ADXL1005 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, approximately
every 500 μs (see Figure 18).
MECHANICAL CONSIDERATIONS FOR MOUNTING
Mount the ADXL1005 on the PCB in a location close to a hard
mounting point of the PCB. Mounting the ADXL1005 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.
MOUNTING POINTS
PCB
A
CCELEROMETERS
16589-012
Figure 24. Incorrectly Placed Accelerometers
Data Sheet ADXL1005
Rev. 0 | Page 13 of 14
LAYOUT AND DESIGN RECOMMENDATIONS
Figure 25 shows the recommended PCB land pattern.
24
23
22
21
20
19
18
17
1
2
3
4
5
6
7
8
32 31 30 29 26 25
9 10111213141516
28 27
0.146/3.7mm 0.191/4.855mm
0.146/3.7mm
0.012/0.305mm
0.02/0.5mm
0.03/0.755mm
0.191/4.855mm
16589-013
Figure 25. Recommended PCB Land Pattern
ADXL1005 Data Sheet
Rev. 0 | Page 14 of 14
OUTLINE DIMENSIONS
02-02-2017-A
1
0.50
BSC
BOTTOM VIEWTOP VIEW
PIN 1
INDICATOR 32
9
16
17
24
25
8
EXPOSED
PAD
0.05 MAX
0.02 NOM
0.203 REF
COPLANARITY
0.08
0.30
0.25
0.20
5.10
5.00 SQ
4.90
*1.85
1.80
1.75
0.45
0.40
0.35
0.20 MIN
3.80
3.70 SQ
3.60
PKG-004829
3.50 REF
*COMPLIANT
TO
JEDEC STANDARDS MO-220-VHHD-4
WITH EXCEPTION TO PACKAGE HEIGHT.
SEATING
PLANE
PIN 1
INDICATOR AREA OPTIONS
(SEE DETAIL A)
DETAIL A
(JEDEC 95)
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
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 g Range Package Description Package Option
ADXL1005BCPZ −40°C to +125°C ±100 g 32-Lead Lead Frame Chip Scale Package [LFCSP] CP-32-26
ADXL1005BCPZ-RL −40°C to +125°C ±100 g 32-Lead Lead Frame Chip Scale Package [LFCSP] CP-32-26
ADXL1005BCPZ-RL7 −40°C to +125°C ±100 g 32-Lead Lead Frame Chip Scale Package [LFCSP] CP-32-26
EVAL-ADXL1005Z ADXL1005 Evaluation Board
1 Z = RoHS Compliant Part.
©2018 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D16589-0-4/18(0)