Precision 18 g Single-/Dual-Axis iMEMS Accelerometer ADW22035/ADW22037 FEATURES FUNCTIONAL BLOCK DIAGRAMS 5V High performance, single-/dual-axis accelerometer on a single IC chip Low power: 740 A at VS = 5 V (typical) High zero g bias stability High sensitivity accuracy -40C to +125C temperature range X and Y axes aligned to within 0.1 (typical) BW adjustment with a single capacitor Single-supply operation 3500 g shock survival RoHS-compliant Compatible with Sn/Pb- and Pb-free solder processes 5 mm x 5 mm x 2 mm LCC package VS ADW22035 CDC OUTPUT AMP COM 07755-001 RFILT 32k ST XOUT CX Figure 1. 5V VS ADW22037 CDC AC AMP GENERAL DESCRIPTION DEMOD OUTPUT AMP OUTPUT AMP SENSOR RFILT 32k COM ST RFILT 32k 07755-101 The ADW22035/ADW22037 are high precision, low power, complete single- and dual-axis iMEMS(R) accelerometers with signal conditioned voltage outputs, all on a single, monolithic IC. The ADW22035/ADW22037 measure acceleration with a full-scale range of 18 g. The ADW22035/ADW22037 can measure both dynamic acceleration, such as vibration, and static acceleration, such as gravity. DEMOD SENSOR APPLICATIONS Vibration monitoring and compensation Abuse event detection Sports equipment Vehicle dynamic control AC AMP YOUT XOUT CY CX Figure 2. The user selects the bandwidth of the accelerometer using Capacitor CX and Capacitor CY at the XOUT and YOUT pins. Bandwidths of 0.5 Hz to 2.5 kHz can be selected to suit the application. The ADW22035/ADW22037 are available in 5 mm x 5 mm x 2 mm, 8-terminal hermetic LCC packages. Rev. 0 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. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2008 Analog Devices, Inc. All rights reserved. ADW22035/ADW22037 TABLE OF CONTENTS Features .............................................................................................. 1 Performance ...................................................................................8 Applications ....................................................................................... 1 Applications Information .................................................................9 General Description ......................................................................... 1 Power Supply Decoupling ............................................................9 Functional Block Diagrams ............................................................. 1 Setting the Bandwidth Using CX and CY ....................................9 Revision History ............................................................................... 2 Self Test ...........................................................................................9 Specifications..................................................................................... 3 Design Trade-Offs for Selecting Filter Characteristics: The Noise/BW Trade-Off .....................................................................9 Absolute Maximum Ratings............................................................ 4 Thermal Resistance ...................................................................... 4 ESD Caution .................................................................................. 4 Pin Configurations and Function Descriptions ........................... 5 Typical Performance Characteristics ............................................. 6 Using the ADW22035/ADW22037 with Operating Voltages Other than 5 V ............................................................................ 10 Outline Dimensions ....................................................................... 11 Ordering Guide .......................................................................... 11 Theory of Operation ........................................................................ 8 REVISION HISTORY 10/08--Revision 0: Initial Version Rev. 0 | Page 2 of 12 ADW22035/ADW22037 SPECIFICATIONS TA = -40C to +125C, VS = 5 V, CX = CY = 0.1 F, acceleration = 0 g, unless otherwise noted. Table 1. Parameter SENSOR INPUT Measurement Range 2 Nonlinearity Package Alignment Error Alignment Error (ADW22037) Cross-Axis Sensitivity SENSITIVITY (RATIOMETRIC) 3 Sensitivity at XOUT, YOUT Sensitivity Change Due to Temperature 4 ZERO g BIAS LEVEL (RATIOMETRIC) 0 g Voltage at XOUT, YOUT Initial 0 g Output Deviation from Ideal 0 g Offset vs. Temperature NOISE PERFORMANCE Output Noise Noise Density FREQUENCY RESPONSE 5 CX, CY Range 6 RFILT Tolerance Sensor Resonant Frequency SELF-TEST (ST) 7 Logic Input Low Logic Input High ST Input Resistance to Ground Output Change at XOUT, YOUT OUTPUT AMPLIFIER Output Swing Low Output Swing High POWER SUPPLY Operating Voltage Range Quiescent Supply Current Turn-On Time 8 Conditions Each axis Min 1 Typ Max1 0.2 1 0.1 1.5 1.25 18 % of full scale X sensor to Y sensor Each axis VS = 5 V VS = 5 V Each axis VS = 5 V VS = 5 V, 25C 3 100 0.3 106 mV/g % 2.4 2.5 125 1 2.6 V mg mg/C 2 mV rms g/Hz rms 10 40 F k kHz 1 130 0.002 24 No load No load 4 30 60 0.05 32 5.5 50 80 100 V V k mV 0.2 4.5 4.8 V V 3 0.7 20 1 g % Degrees Degrees % 94 <4 kHz, VS = 5 V Self-Test 0 to Self-Test 1 Unit 6 1.1 V mA ms All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed. Guaranteed by measurement of initial offset and sensitivity. Sensitivity is essentially ratiometric to VS. For VS = 4.75 V to 5.25 V, sensitivity is 18.6 mV/V/g to 21.5 mV/V/g. 4 Defined as the output change from ambient-to-maximum temperature or ambient-to-minimum temperature. 5 Actual frequency response controlled by user-supplied external capacitor (CX, CY). 6 Bandwidth = 1/(2 x x 32 k x C). For CX, CY = 0.002 F, bandwidth = 2500 Hz. For CX, CY = 10 F, bandwidth = 0.5 Hz. Minimum/maximum values are not tested. 7 Self-test response changes cubically with VS. 8 Larger values of CX, CY increase turn-on time. Turn-on time is approximately 160 x CX or CY + 4 ms, where CX, CY are in F. 2 3 Rev. 0 | Page 3 of 12 ADW22035/ADW22037 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 2. Parameter Acceleration (Any Axis, Unpowered) Acceleration (Any Axis, Powered) Drop Test (Concrete Surface) VS All Other Pins Output Short-Circuit Duration (Any Pin to Common) Temperature Range (Powered) Temperature Range (Storage) Rating 3500 g 3500 g 1.2 m -0.3 V to +7.0 V (COM - 0.3 V) to (VS + 0.3 V) JA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Indefinite -55C to +125C -65C to +150C ESD CAUTION Table 3. Thermal Resistance Package Type 8-Terminal Ceramic LCC JA 120C/W Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. CRITICAL ZONE TL TO TP tP TP TEMPERATURE RAMP-UP TL tL TSMAX TSMIN tS RAMP-DOWN PREHEAT T25C TO PEAK TIME Sn63/Pb37 Pb-Free Average Ramp Rate (T L to TP) 3C/sec max 3C/sec max Preheat Minimum Temperature (T SMIN) Maximum Temperature (T SMAX) Time (TSMIN to TSMAX)(tS) 100C 150C 60 to 120 s 150C 200C 60 to 150 s TSMIN to TL Ramp-Up Rate 3C/sec max 3C/sec max Time Maintained above Liquidous (TL) Liquidous Temperature (T L) Time (tL) 183C 60 to 150 s 217C 60 to 150 s Peak Temperature (T P) 240C + 0C/-5C 260C + 0C/-5C Time Within 5C of Actual Peak Temperature ( tP) 10s to 30 s 20s to 40 s Ramp-Down Rate 6C/sec max 6C/sec max Time 25C to Peak Temperature 6 minutes max 8 minutes max Figure 3. Recommended Soldering Profile Rev. 0 | Page 4 of 12 07755-002 Condition Profile Feature JC 20C/W Device Weight <1.0 gram ADW22035/ADW22037 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS ADW22035 TOP VIEW (Not to Scale) ST 1 DNC 2 COM 3 8 +X 4 7 XOUT 6 DNC 5 DNC DNC DNC = DO NOT CONNECT 07755-003 VS Figure 4. ADW22035 Pin Configuration Table 4. ADW22035 Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 Mnemonic ST DNC COM DNC DNC DNC XOUT VS Description Self Test Do Not Connect Common Do Not Connect Do Not Connect Do Not Connect X Channel Output 3 V to 6 V ADW22037 TOP VIEW (Not to Scale) ST 1 DNC 2 COM 3 8 +Y +X 4 7 XOUT 6 YOUT 5 DNC DNC DNC = DO NOT CONNECT 07755-004 VS Figure 5. ADW22037 Pin Configuration Table 5. ADW22037 Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 Mnemonic ST DNC COM DNC DNC YOUT XOUT VS Description Self Test Do Not Connect Common Do Not Connect Do Not Connect Y Channel Output X Channel Output 3 V to 6 V Rev. 0 | Page 5 of 12 ADW22035/ADW22037 TYPICAL PERFORMANCE CHARACTERISTICS 60 50 50 35 30 30 20 20 50 07755-008 40 30 Figure 8. X-Axis Sensitivity at 25C Figure 11. Y-Axis Sensitivity at 25C Rev. 0 | Page 6 of 12 07755-009 2.5 2.0 3.0 103 07755-010 (mV/g) 102 97 07755-007 103 0 102 0 101 5 100 5 101 10 100 10 15 99 15 98 PERCENT OF POPULATION 25 99 1.5 Figure 10. Y-Axis Zero g Bias Tempco 25 98 1.0 (mg/C) Figure 7. X-Axis Zero g Bias Tempco 97 0 -3.0 3.5 07755-006 3.0 2.5 1.5 2.0 1.0 0.5 0 -0.5 -1.0 0 -1.5 0 -2.0 5 -2.5 5 0.5 10 -0.5 10 15 -1.0 15 20 -1.5 20 25 -2.0 25 -2.5 PERCENT OF POPULATION 35 -3.0 PERCENT OF POPULATION Figure 9. Y-Axis Zero g Bias Deviation from Ideal at 25C (mg/C) PERCENT OF POPULATION 20 (mV) Figure 6. X-Axis Zero g Bias Deviation from Ideal at 25C (mV/g) 0 -50 50 (mV) 07755-005 40 30 20 10 0 -10 0 -20 0 -30 10 -40 10 10 20 -10 20 30 -20 30 40 -30 40 -40 PERCENT OF POPULATION 60 -50 PERCENT OF POPULATION VS = 5 V for all graphs, unless otherwise noted. 45 35 40 15 0.100 (V) Figure 15. Y-Axis Self-Test Response at 25C Figure 12. X-Axis Self-Test Response at 25C 101.0 100.0 VOLTAGE (V) SENSITIVITY (mV) 100.5 99.5 99.0 98.5 97.5 -50 -25 0 25 50 TEMPERATURE (C) 75 100 125 07755-012 07755-015 98.0 Figure 13. Sensitivity vs. Temperature; Parts Soldered to PCB Figure 16. Turn-On Time: CX, CY = 0.1 F, Time Scale = 2 ms/div 90 25C 105C 70 60 50 40 30 20 10 960 07755-013 (A) 940 920 900 880 860 840 820 800 780 760 740 720 700 0 680 PERCENT OF POPULATION 80 TIME (2ms/DIV) Figure 14. Supply Current vs. Temperature Rev. 0 | Page 7 of 12 07755-014 0.060 0.100 (V) 07755-011 0.095 0.090 0.085 0.080 0 0.075 0 0.070 5 0.065 5 0.095 10 0.090 10 20 0.085 15 25 0.080 20 30 0.075 25 35 0.070 30 0.065 PERCENT OF POPULATION 40 0.060 PERCENT OF POPULATION ADW22035/ADW22037 ADW22035/ADW22037 THEORY OF OPERATION The ADW22035/ADW22037 is a complete acceleration measurement system on a single, monolithic IC. The ADW22035/ADW22037 is a dual-axis accelerometer. This device contains a polysilicon surface-micromachined sensor and signal conditioning circuitry to implement an open-loop acceleration measurement architecture. The output signals are analog voltages proportional to acceleration. The ADW22035/ ADW22037 are capable of measuring both positive and negative accelerations to at least 18 g. The sensor is a surface-micromachined polysilicon structure built on top of the 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 a differential capacitor that consists of independent fixed plates and plates attached to the moving mass. The fixed plates are driven by 180 out-of-phase square waves. Acceleration deflects the beam and unbalances the differential capacitor, resulting in an output square wave whose amplitude is proportional to acceleration. Phase-sensitive demodulation techniques are then used to rectify the signal and determine the direction of the acceleration. The output of the demodulator is amplified and brought off-chip through a 32 k resistor. At this point, the user can set the signal bandwidth of the device by adding a capacitor. This filtering improves measurement resolution and helps prevent aliasing. PERFORMANCE Rather than using additional temperature compensation circuitry, innovative design techniques ensure that high performance is built in to these devices. As a result, there is essentially no quantization error or nonmonotonic behavior, and temperature hysteresis is very low (typically less than 15 mg over the -40C to +125C temperature range). Figure 17 demonstrates the typical sensitivity shift over temperature for VS = 5 V. Sensitivity stability is optimized for VS = 5 V, but is still very good over the specified range; it is typically better than 1% over temperature at VS = 3 V. PIN 8 XOUT = 2.4V YOUT = 2.5V TOP VIEW (Not to Scale) PIN 8 XOUT = 2.5V YOUT = 2.4V XOUT = 2.5V YOUT = 2.5V PIN 8 XOUT = 2.6V YOUT = 2.5V EARTH'S SURFACE Figure 17. Output Response vs. Orientation Rev. 0 | Page 8 of 12 07755-021 PIN 8 XOUT = 2.5V YOUT = 2.6V ADW22035/ADW22037 APPLICATIONS INFORMATION POWER SUPPLY DECOUPLING For most applications, a single 0.1 F capacitor, CDC, adequately decouples the accelerometer from noise on the power supply. However in some cases, particularly where noise is present at the 140 kHz internal clock frequency (or any harmonic thereof), noise on the supply can cause interference on the ADW22037 output. If additional decoupling is needed, a 100 (or smaller) resistor or ferrite beads can be inserted in the supply line of the ADW22035/ADW22037. Additionally, a larger bulk bypass capacitor (in the 1 F to 22 F range) can be added in parallel to CDC. SETTING THE BANDWIDTH USING CX AND CY The ADW22035/ADW22037 have provisions for band limiting the XOUT and YOUT pins. Capacitors must be added at these pins to implement low-pass filtering for antialiasing and noise reduction. The equation for the 3 dB bandwidth is F-3 dB = 1/(2(32 k) x C(X, Y)) or more simply, F-3 dB = 5 F/C(X, Y) The tolerance of the internal resistor (RFILT) can vary typically as much as 25% of its nominal value (32 k); thus, the bandwidth varies accordingly. A minimum capacitance of 2000 pF for CX and CY is required in all cases. DESIGN TRADE-OFFS FOR SELECTING FILTER CHARACTERISTICS: THE NOISE/BW TRADE-OFF The accelerometer bandwidth selected ultimately determines the measurement resolution (smallest detectable acceleration). Filtering can be used to lower the noise floor, improving the resolution of the accelerometer. Resolution is dependent on the analog filter bandwidth at XOUT and YOUT. The output of the ADW22035/ADW22037 has a typical bandwidth of 2.5 kHz. The user must filter the signal at this point to limit aliasing errors. The analog bandwidth must be no more than half the analog-to-digital sampling frequency to minimize aliasing. The analog bandwidth can be further decreased to reduce noise and improve resolution. The ADW22035/ADW22037 noise has the characteristics of white Gaussian noise, which contributes equally at all frequencies and is described in terms of g/Hz (that is, the noise is proportional to the square root of the accelerometer bandwidth). The user should limit bandwidth to the lowest frequency needed by the application to maximize the resolution and dynamic range of the accelerometer. With the single pole roll-off characteristic, the typical noise of the ADW22035/ADW22037is determined by rmsNoise = (130 g / Hz ) x ( BW x1.6 ) At 100 Hz, the noise is rmsNoise = (130 g / Hz ) x ( 100 x1.6 ) = 1.64 mg Table 6. Filter Capacitor Selection, CX and CY Bandwidth (Hz) 1 10 50 100 200 500 Capacitor (F) 4.7 0.47 0.10 0.05 0.027 0.01 Often, the peak value of the noise is desired. Peak-to-peak noise can only be estimated by statistical methods. Table 7 is useful for estimating the probabilities of exceeding various peak values, given the rms value. Table 7. Estimation of Peak-to-Peak Noise SELF TEST The ST pin controls the self-test feature. When this pin is set to VS, an electrostatic force is exerted on the beam of the accelerometer. The resulting movement of the beam allows the user to test if the accelerometer is functional. The typical change in output is 800 mg (corresponding to 80 mV). This pin can be left open-circuit or connected to common in normal use. Peak-to-Peak Value 2 x rms 4 x rms 6 x rms 8 x rms The ST pin should never be exposed to voltage greater than VS + 0.3 V. If the system design is such that this condition cannot be guaranteed (that is, multiple supply voltages are present), a low VF clamping diode between ST and VS is recommended. Rev. 0 | Page 9 of 12 % of Time That Noise Exceeds Nominal Peak-to-Peak Value 32 4.6 0.27 0.006 ADW22035/ADW22037 Peak-to-peak noise values provide the best estimate of the uncertainty in a single measurement. Peak-to-peak noise is estimated by 6 x rms. Table 8 gives the typical noise output of the ADW22035/ADW22037 for various CX and CY values. The ADW22035/ADW22037 output is ratiometric, thus the output sensitivity (or scale factor) varies proportionally to the supply voltage. At VS = 3 V the output sensitivity is typically 56 mV/g. Table 8. Filter Capacitor Selection (CX, CY) The zero g bias output is also ratiometric, thus the zero g output is nominally equal to VS/2 at all supply voltages. Bandwidth (Hz) 10 50 100 500 CX, CY (F) 0.47 0.1 0.047 0.01 RMS Noise (mg) 0.5 1.2 1.6 3.7 Peak-to-Peak Noise Estimate (mg) 3.0 7.2 9.6 22.2 USING THE ADW22035/ADW22037 WITH OPERATING VOLTAGES OTHER THAN 5 V The ADW22035/ADW22037 are tested and specified at VS = 5 V; however, it can be powered with VS as low as 3 V or as high as 6 V. Some performance parameters change as the supply voltage is varied. The output noise is not ratiometric but is absolute in volts; therefore, the noise density decreases as the supply voltage increases. This is because the scale factor (mV/g) increases while the noise voltage remains constant. At VS = 3 V, the noise density is typically 240 g/Hz. Self-test response in g is roughly proportional to the square of the supply voltage. However, when ratiometricity of sensitivity is factored in with supply voltage, self-test response in volts is roughly proportional to the cube of the supply voltage. Thus, at VS = 3 V, the self-test response is approximately equivalent to 15 mV or equivalent to 270 mg (typical). Rev. 0 | Page 10 of 12 ADW22035/ADW22037 OUTLINE DIMENSIONS 0.203 0.197 SQ 0.193 0.087 0.078 0.069 0.20 0.15 0.10 (R 4 PLCS) 0.054 0.050 0.046 0.028 0.020 DIA 0.012 7 0.180 0.177 SQ 0.174 1 0.106 0.100 0.094 0.075 REF R 0.008 (8 PLCS) TOP VIEW 0.008 0.006 0.004 5 3 BOTTOM VIEW 0.077 0.070 0.063 091307-B R 0.008 (4 PLCS) 0.030 0.025 0.020 Figure 18. 8-Terminal Ceramic Leadless Chip Carrier [LCC] (E-8-1) Dimensions shown in inches ORDERING GUIDE Model ADW22035Z 1 ADW22035Z-RL1 ADW22035Z-RL71 ADW22037Z1 ADW22037Z-RL1 ADW22037Z-RL71 1 Number of Axes 1 1 1 2 2 2 Specified Voltage (V) 5 5 5 5 5 5 Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C Package Description 8-Terminal Ceramic Leadless Chip Carrier [LCC] 8-Terminal Ceramic Leadless Chip Carrier [LCC] 8-Terminal Ceramic Leadless Chip Carrier [LCC) 8-Terminal Ceramic Leadless Chip Carrier [LCC] 8-Terminal Ceramic Leadless Chip Carrier [LCC] 8-Terminal Ceramic Leadless Chip Carrier [LCC] Z = RoHS Compliant Part. Rev. 0 | Page 11 of 12 Package Option E-8-1 E-8-1 E-8-1 E-8-1 E-8-1 E-8-1 ADW22035/ADW22037 NOTES (c)2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07755-0-10/08(0) Rev. 0 | Page 12 of 12