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Low Noise, Wide Bandwidth, MEMS Accelerometer Data Sheet ADXL1005 Rev. 0 Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Tel: 781.329.4700 ©2018 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com
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
Health usage monitoring systems (HUMSs) Acoustic emissions FUNCTIONAL BLOCK DIAGRAM TIMING GENERATOR ADXL1005 XOUT OR SENSORMOD AMP SELF TEST ST VSS OUTPUT AMPLIFIERDEMOD OVERRANGE DETECTION VDD 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.
Rev. 0 | Page 2 of 14 TABLE OF CONTENTS
REVISION HISTORY
4/2018—Revision 0: Initial Version
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 V DD/2 V 0 g Output Range over Temperature4 −40°C to +125°C 9 g NOISE Noise Density 100 Hz to 20 kHz 75 μ g/√Hz 100 Hz to 20 kHz, at 3.0 V supply 125 μ g/√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 VDD × 0.3 V Input Current 25 μA OUTPUT AMPLIFIER Short-Circuit Current 3 mA Output Impedance <0.1 Ω Maximum Resistive Load 20 MΩ 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.
PCB thermal design is required. resistance measured in a one cubic foot sealed enclosure. θJC is the junction to case thermal resistance. Table 3. Package Characteristics
1 Thermal impedance simulated values are based on a JEDEC 2S2P thermal
test board with nine thermal vias. See JEDEC JESD51. Figure 2. Recommended Soldering Profile Table 4. Recommended Soldering Profile
- NIC = NOT INTERNALLY CONNECTED.
- DNC = DO NOT CONNECT. LEAVE THIS PIN UNCONNECTED.
- EXPOSED PAD. THE EXPOSED PAD ON THE BOTTOM OF
- AXIS OF SENSITIVITY IS IN PLANE TO THE PACKAGE
24 DNC
23 DNC
22 DNC
21 DNC
19 DNC
18 DNC
17 DNC
Figure 3. Pin Configuration Table 5. Pin Function Descriptions 1 to 9, 31, 32 NIC Not Internally Connected. DNC Do Not Connect. Leave this pin unconnected. 12 V DD 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. identifies significant overrange activity. This pin is not latched. 30 X OUT Analog Output Voltage. required for both electrical and mechanical performance.
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 (HV AC) 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.
signal processing of the electrical output. monitored (either in a module or directly mounted). Provide multiple hard mounting points. induces higher magnitude and lower frequency resonances. transfer mechanical forces up to the desired frequency. boards can be used as a reference. faster than the amplifier bandwidth. supply and reference voltage induced error cancels out. This design approach is recommended. greater than 100 pF , an 8 kΩ or greater series resistor must be used. are properly attenuated and do not alias into the band. nents when measuring mechanical vibration from 0 kHz to 10 kHz. sample rate of 200 kHz is recommended to avoid aliasing. *3.0V LIMITED BY ADXL1005; 5.1V LIMITED BY ADAQ7980. Figure 23. Application Circuit for the ADXL1005
mechanical transfer of vibration through these frequencies. Mechanical system analysis is required for these applications. appropriate filtering is required for optimal performance. output response to an input stimulus peaks, as shown in Figure 4. additional external low-pass filtering is required. not to affect the analysis of results. digital low-pass filtering to achieve similar performance. every 500 μs (see Figure 18). effect of system resonance on the performance of the sensor. Figure 24. Incorrectly Placed Accelerometers
0.05 MAX
0.02 NOM
0.203 REF
0.20 MIN
3.50 REF
WITH EXCEPTION TO PACKAGE HEIGHT. Figure 26. 32-Lead Lead Frame Chip Scale Package [LFCSP] registered trademarks are the prop erty of their respective owners.