Low Noise, Wide Bandwidth, MEMS Accelerometer ADXL1005 Data Sheet FEATURES FUNCTIONAL BLOCK DIAGRAM VDD STANDBY ADXL1005 TIMING GENERATOR MOD SENSOR AMP OUTPUT AMPLIFIER DEMOD OVERRANGE DETECTION XOUT OR SELF TEST VSS ST 16589-001 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 g/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 -40C to +125C operating temperature range 32-lead, 5 mm x 5 mm x 1.8 mm LFCSP package Figure 1. APPLICATIONS Condition monitoring Predictive maintenance Asset health Test and measurement Health usage monitoring systems (HUMSs) Acoustic emissions 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 g/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. Rev. 0 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 x 5 mm x 1.8 mm LFCSP package, and operates over the -40C to +125C temperature range. 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Technical Support www.analog.com ADXL1005 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Operating Modes ...........................................................................9 Applications ....................................................................................... 1 Bandwidth ......................................................................................9 Functional Block Diagram .............................................................. 1 Applications Information .............................................................. 10 General Description ......................................................................... 1 Application Circuit ..................................................................... 10 Revision History ............................................................................... 2 On Demand Self Test ................................................................. 10 Specifications..................................................................................... 3 Ratiometric Output Voltage ...................................................... 10 Absolute Maximum Ratings............................................................ 4 Interfacing Analog Output Below 10 kHz .............................. 11 Thermal Resistance ...................................................................... 4 Interfacing Analog Output Beyond 10 kHz ............................ 12 Recommended Soldering Profile ............................................... 4 Overrange .................................................................................... 12 ESD Caution .................................................................................. 4 Mechanical Considerations for Mounting .............................. 12 Pin Configuration and Function Descriptions ............................. 5 Layout and Design Recommendations ................................... 13 Typical Performance Characteristics ............................................. 6 Outline Dimensions ....................................................................... 14 Theory of Operation ........................................................................ 9 Ordering Guide .......................................................................... 14 Mechanical Device Operation .................................................... 9 REVISION HISTORY 4/2018--Revision 0: Initial Version Rev. 0 | Page 2 of 14 Data Sheet ADXL1005 SPECIFICATIONS TA = 25C, 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 SENSOR Measurement Range Linearity1 Cross Axis Sensitivity2 SENSITIVITY (RATIOMETRIC TO VDD) Sensitivity Sensitivity Change Due to Temperature3 ZERO g OFFSET (RATIOMETRIC TO VDD) 0 g Output Voltage 0 g Output Range over Temperature4 NOISE Noise Density 1/f Frequency Corner FREQUENCY RESPONSE Sensor Resonant Frequency 5% Bandwidth5 3 dB Bandwidth6 SELF TEST Output Change (Ratiometric to VDD) Input Voltage Level High, VIH Low, VIL Input Current OUTPUT AMPLIFIER Short-Circuit Current Output Impedance Maximum Resistive Load Maximum Capacitive Load7 POWER SUPPLY (VDD) Operating Voltage Range Quiescent Supply Current Standby Current Standby Recovery Time (Standby to Measure Mode) Turn On Time8 OPERATING TEMPERATURE RANGE Test Conditions/Comments Min Typ Max Unit Percentage of full-scale Z-axis acceleration effect on x-axis Y-axis acceleration effect on x-axis 100 0.25 0.7 1.5 g % % % DC TA = -40C to +125C 20 5 mV/g % -40C to +125C VDD/2 9 V g 75 125 0.1 g/Hz g/Hz Hz 37.7 42 9 23 kHz kHz kHz 420 490 mV 100 Hz to 20 kHz 100 Hz to 20 kHz, at 3.0 V supply ST low to ST high VDD x 0.7 25 V V A 3 <0.1 20 100 22 mA M pF nF VDD x 0.3 No external resistor With external resistor 3.0 Output settled to 1% of final value -40 1 5.0 1.0 225 <50 <550 5.25 1.15 285 +125 V mA A s s C Linearity is tested using sine vibration at 100 Hz. 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 25C. 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 k). 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. 2 Rev. 0 | Page 3 of 14 ADXL1005 Data Sheet ABSOLUTE MAXIMUM RATINGS Table 4. Recommended Soldering Profile Table 2. Parameter Acceleration Mechanical Shock: Any Axis, Powered or Unpowered per IEC 60068-2-27 Drop Test (Concrete Surface), per AEC-Q100 Test G5 VDD Output Short-Circuit Duration (Any Pin to Common Ground) Temperature Range (Storage) Rating Profile Feature Average Ramp Rate (TL to TP) 10,000 g Preheat Minimum Temperature (TSMIN) Maximum Temperature (TSMAX) Time (TSMIN to TSMAX)(tS) 1.2 m -0.3 V to +5.5 V Indefinite TSMAX to TL Ramp-Up Rate -55C to +150C 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. JA is the natural convection junction to ambient thermal resistance measured in a one cubic foot sealed enclosure. JC is the junction to case thermal resistance. Time Maintained Above Liquidous (TL) Liquidous Temperature (TL) Time (tL) Peak Temperature (TP) Time Within 5C of Actual Peak Temperature (tP) Ramp-Down Rate Time 25C to Peak Temperature (t25C) ESD CAUTION Table 3. Package Characteristics Package Type CP-32-261 1 JA 48C/W JC 14.1C/W Device Weight <0.2 g 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. CRITICAL ZONE TL TO TP tP TP TL tL TSMAX TSMIN tS RAMP-DOWN PREHEAT t25C TO PEAK TIME 16589-002 TEMPERATURE RAMP-UP Figure 2. Recommended Soldering Profile Rev. 0 | Page 4 of 14 Condition Sn63/Pb37 Pb-Free 3C/sec 3C/sec maximum maximum 100C 150C 60 sec to 120 sec 150C 200C 60 sec to 180 sec 3C/sec maximum 3C/sec maximum 183C 60 sec to 150 sec 240 + 0/-5C 10 sec to 30 sec 6C/sec maximum 6 min maximum 217C 60 sec to 150 sec 260 + 0/-5C 20 sec to 40 sec 6C/sec maximum 8 min maximum Data Sheet ADXL1005 32 31 30 29 28 27 26 25 NIC NIC XOUT DNC VSS VSS DNC DNC PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 1 2 3 4 5 6 7 8 + - ADXL1005 TOP VIEW (Not to Scale) 24 23 22 21 20 19 18 17 DNC DNC DNC DNC OR DNC DNC 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. 16589-003 NIC DNC DNC VDD VSS VSS STANDBY ST 9 10 11 12 13 14 15 16 NIC NIC NIC NIC NIC NIC NIC NIC Figure 3. Pin Configuration Table 5. Pin Function Descriptions Pin No. 1 to 9, 31, 32 10, 11, 17 to 19, 21 to 26, 29 12 13, 14, 27, 28 15 16 20 Mnemonic NIC DNC Description Not Internally Connected. Do Not Connect. Leave this pin unconnected. VDD VSS STANDBY ST OR 30 XOUT EPAD 3.0 V to 5.25 V Supply Voltage. Supply Ground. 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. Analog Output Voltage. 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 ADXL1005 Data Sheet 5.0 50 4.5 45 4.0 40 PERCENT OF POPULATION (%) 3.5 3.0 2.5 2.0 1.5 1.0 30 25 20 15 10 5 0.5 10 100 1k 10k 0 16589-004 0 35 100k FREQUENCY (Hz) 19.0 19.2 19.4 19.6 19.8 20.0 20.2 20.4 20.6 20.8 21.0 SENSITIVITY DISTRIBUTION (mV/g) Figure 7. Sensitivity Distribution at 25C Figure 4. Frequency Response, High Frequency (>5 kHz) Vibration Response; a Laser Vibrometer Controller Referencing the ADXL1005 Package Used for Accuracy NOISE POWER SPECTRAL DENSITY (g/Hz) 100000 16589-014 NORMALIZED AMPLITUDE (OUTPUT (g)/REFERENCE (g)) TYPICAL PERFORMANCE CHARACTERISTICS 1000 DUT 1 DUT 2 NOISE PSD (g/Hz) 10000 1000 100 100 0.1 1 10 100 16589-006 1 0.01 10 FREQUENCY (Hz) 1k 0.5 2.5 0 40 20 0 20 40 60 TEMPERATURE (C) 80 100 120 16589-025 -2.5 Figure 6. Sensitivity vs. Temperature 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 20 40 60 80 100 INPUT ACCELERATION (g) Figure 9. Sensitivity Nonlinearity vs. Input Acceleration Rev. 0 | Page 6 of 14 120 16589-009 SENSITIVITY NONLINEARITY (% of Full Scale) 5.0 SENSITIVITY (%) 100k Figure 8. Noise PSD Above 100 Hz Figure 5. Noise Power Spectral Density (PSD) Below 10 Hz vs. Frequency -5.0 10k FREQUENCY (Hz) 16589-005 10 Data Sheet ADXL1005 10 35 8 30 PERCENT OF POPULATION (%) NORMALIZED OFFSET (g) 6 4 2 0 -2 -4 -6 25 20 15 10 5 40 20 0 20 40 60 80 100 120 TEMPERATURE (C) 0 16589-024 -10 2.48 2.49 Figure 10. Normalized Offset vs. Temperature 2.53 2.52 280 1050 260 STANDBY CURRENT (A) 1000 950 900 850 800 750 240 220 200 180 700 600 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 SUPPLY VOLTAGE (V) 140 3.0 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 SUPPLY VOLTAGE (V) Figure 11. Measure Mode Supply Current vs. Supply Voltage Figure 14. Standby Current vs. Supply Voltage 40 35 35 PERCENT OF POPULATION (%) 30 30 25 20 15 10 25 20 15 10 940 960 980 1000 1020 1040 1060 1080 1100 MEASURE MODE CURRENT (A) 0 16589-016 920 212 216 220 224 228 232 236 240 244 STANDBY CURRENT (A) Figure 12. Measure Mode Current Histogram at 25C Figure 15. Standby Current Histogram at 25C Rev. 0 | Page 7 of 14 248 16589-015 5 5 0 3.2 16589-023 160 650 16589-022 MEASURE MODE SUPPLY CURRENT (A) 2.51 Figure 13. 0 g Offset Histogram at 25C 1100 PERCENT OF POPULATION (%) 2.50 0g OUTPUT DISTRIBUTION (V) 16589-017 -8 ADXL1005 Data Sheet 300 4 200 XOUT 2 1 STANDBY 2 50 0 -1 -50 5 10 15 20 25 30 35 40 TIME (s) 208 INTERNAL CLOCK FREQUENCY (kHz) 215 210 205 200 195 190 100 150 16589-019 185 50 TEMPERATURE (C) 0 -1 10 5 TIME (ms) 210 0 0 Figure 18. Response to Overload Condition, XOUT Delta is Difference from Midscale Voltage 220 180 -50 1 -100 -5 16589-026 0 Figure 16. XOUT Output Recovery from Standby Mode to Measure Mode INTERNAL CLOCK FREQUENCY, VDD = 5.0V (kHz) 3 100 0 -2 4 150 Figure 17. Internal Clock Frequency vs. Temperature at 5.0 V Supply Voltage (VDD) Rev. 0 | Page 8 of 14 206 204 202 200 198 196 194 193 190 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) Figure 19. Internal Clock Frequency vs. Supply Voltage at 25C 16589-020 3 5 OUTPUT (V) 250 6 REFERENCE (g) XOUT (g) OR OUTPUT (V) 16589-008 5 ACCELERATION (g) VOLTAGE (V) 6 Data Sheet ADXL1005 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 information 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 surfacemicromachined 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 amplitude 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 measurement and reduces the internal current consumption to 225 A (typical for the 5.0 V supply). The transition time from standby to measurement mode is <50 s. 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 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. 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. Rev. 0 | Page 9 of 14 ADXL1005 Data Sheet APPLICATIONS INFORMATION 4. APPLICATION CIRCUIT For most applications, a single 1 F 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 k 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 k is required to maintain the amplifier stability. 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 s from the assertion of the ST pin to a result. Acceleration outputs return approximately 300 s after the release of the ST pin. While performing the self test measurement, do not use the accelerometer output to measure external acceleration. 0.8 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. SELF TEST DELTA (mV) 0.6 OPTIONAL LOW-PASS FILTER R VOUT C VSS 29 28 27 26 25 24 2 23 3 22 0 3.0 5 19 7 18 8 12 13 14 1F 15 16 ST (ACTIVE HIGH) STANDBY (ACTIVE HIGH) 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. 4.0 4.2 4.4 4.6 4.8 5.0 5.2 The ADXL1005 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 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). The self test feature can be exercised by the user with the following steps: 1. 2. 3. 3.8 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. 16589-007 VDD (3.0V TO 5.25V SUPPLY VOLTAGE) 11 3.6 RATIOMETRIC OUTPUT VOLTAGE OR 17 10 3.4 Figure 21. Typical Self Test Delta vs. Supply Voltage 20 6 3.2 SUPPLY VOLTAGE (V) 21 ADXL1005 9 0.2 0.1 1 4 0.3 16589-021 30 0.4 22 20 18 16 14 12 Measure the output voltage. Turn on self test by setting the ST pin to VDD. Measure the output again. 10 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) Figure 22. Sensitivity vs. Supply Voltage Rev. 0 | Page 10 of 14 5.0 16589-122 31 0.5 SENSITIVITY (mV/g) 32 MAXIMUM TYPICAL MINIMUM 0.7 Data Sheet ADXL1005 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 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 k or greater series resistor must be used. See Figure 23 for an example of the interface, including components 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 k, C1 = 330 pF, R2 = 0 , 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 components 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 , C1 = 10,000 pF, R2 = 1 k, and C2 = 10,000 pF. A minimum ADC sample rate of 200 kHz is recommended to avoid aliasing. VDD 3.0V TO 5.1V* 0.1F (+1F, OPTIONAL) 10F VDD XOUT ADXL1005 R1 R2 C1 IN+ C2 REF VSS *3.0V LIMITED BY ADXL1005; 5.1V LIMITED BY ADAQ7980. 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. Rev. 0 | Page 11 of 14 VDD ADAQ7980 IN- The output amplifier is ratiometric to the supply voltage, and there are two distinct cases regarding digital conversion, as follows: ADAQ7980 V DD Figure 23. Application Circuit for the ADXL1005 GND 16589-010 INTERFACING ANALOG OUTPUT BELOW 10 kHz ADXL1005 Data Sheet 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 2x the equivalent noise bandwidth (ENBW) for a single-pole, low-pass filter, as follows: 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 4x 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 2x 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 2x the specified g range. When an overrange is detected, the internal clock is disabled to the sensor for 200 s 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 s (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. ENBW = (/2) x 70 kHz 110 kHz ACCELEROMETERS PCB MOUNTING POINTS Figure 24. Incorrectly Placed Accelerometers Rev. 0 | Page 12 of 14 16589-012 INTERFACING ANALOG OUTPUT BEYOND 10 kHz Data Sheet ADXL1005 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 1 24 2 23 3 22 4 21 5 20 6 19 7 18 8 0.191/4.855mm 17 9 10 11 12 13 14 15 16 0.146/3.7mm 0.191/4.855mm Figure 25. Recommended PCB Land Pattern Rev. 0 | Page 13 of 14 16589-013 0.012/0.305mm 0.146/3.7mm ADXL1005 Data Sheet OUTLINE DIMENSIONS DETAIL A (JEDEC 95) PIN 1 INDICATOR 0.30 0.25 0.20 25 32 24 1 0.50 BSC 3.80 3.70 SQ 3.60 EXPOSED PAD 8 17 TOP VIEW *1.85 1.80 1.75 0.45 0.40 0.35 0.05 MAX 0.02 NOM COPLANARITY 0.08 0.203 REF PKG-004829 SEATING PLANE PIN 1 INDIC ATOR AREA OPTIONS (SEE DETAIL A) 16 9 BOTTOM VIEW 3.50 REF 0.20 MIN FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. *COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-4 WITH EXCEPTION TO PACKAGE HEIGHT. 02-02-2017-A 5.10 5.00 SQ 4.90 Figure 26. 32-Lead Lead Frame Chip Scale Package [LFCSP] 5 mm x 5 mm Body and 1.8 mm Package Height (CP-32-26) Dimensions shown in millimeters ORDERING GUIDE Model1 ADXL1005BCPZ ADXL1005BCPZ-RL ADXL1005BCPZ-RL7 EVAL-ADXL1005Z 1 Temperature Range -40C to +125C -40C to +125C -40C to +125C g Range 100 g 100 g 100 g Package Description 32-Lead Lead Frame Chip Scale Package [LFCSP] 32-Lead Lead Frame Chip Scale Package [LFCSP] 32-Lead Lead Frame Chip Scale Package [LFCSP] ADXL1005 Evaluation Board Z = RoHS Compliant Part. (c)2018 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D16589-0-4/18(0) Rev. 0 | Page 14 of 14 Package Option CP-32-26 CP-32-26 CP-32-26