Single-Axis, High-g, iMEMS® Accelerometers ADXL78 FEATURES GENERAL DESCRIPTION Complete acceleration measurement system on a single The ADXL78 is a low power, complete single-axis accelerometer monolithic IC with signal conditioned voltage outputs that are on a single Available in ±35 g, ±50 g, or ±70 g output full-scale ranges monolithic IC. This product measures acceleration with a full- Full differential sensor and circuitry for high resistance scale range of ±35 g, ±50 g, or ±70 g (minimum). It can also to EMI/RFI measure both dynamic accelerationE (vibration) and static Environmentally robust packaging acceleration (gravity). Complete mechanical and electrical self-test on The ADXL78 is the fourth-generation surface micromachined digital command iMEMS® accelerometer Tfrom ADI with enhanced performance Output ratiometric to supply and lower cost. Designed for use in front and side impact airbag Sensitive axes in the plane of the chip applications, this product also provides a complete cost- High linearity (0.2% of full scale) effective solution useful for a wide variety of other applications. Frequency response down to dc E Low noise The ADXL78 is temperature stable and accurate over the Low power consumption (1.3 mA) automotive temperature range, with a self-test feature that fully Tight sensitivity tolerance and 0 g offset capability exercises all the mechanical and electrical elements of the L Largest available prefilter clipping headroom sensor with a digital signal applied to a single pin. 400 Hz, 2-pole Bessel filter The ADXL78 is available in a 5 mm × 5 mm × 2 mm, Single-supply operation 8-terminal ceramic LCC package. O Compatible with Sn/Pb and Pb-free solder processes Qualified for automotive applications APPLICATIONS Vibration monitoring and control S Vehicle collision sensing Shock detection B FUNCTIONAL BLOCK DIAGRAM VS O ADXL78 TIMING VDD GENERATOR VDD2 400Hz DIFFERENTIAL DEMOD EXC SENSOR AMP BESSEL XOUT FILTER SELF-TEST 05368-001 Figure 1. Rev. B 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. 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. Tel: 781.329.4700 www.analog.com Trademarks and registered trademarks are the property of their respective owners. Fax: 781.461.3113 ©2010 Analog Devices, Inc. All rights reserved.

ADXL78 TABLE OF CONTENTS Features .............................................................................................. 1  Applications ........................................................................................8  Applications ....................................................................................... 1  Power Supply Decoupling ............................................................8  General Description ......................................................................... 1  Self-Test ..........................................................................................8  Functional Block Diagram .............................................................. 1  Clock Frequency Supply Response .............................................8  Specifications ..................................................................................... 3  Signal Distortion ...........................................................................8  Absolute Maximum Ratings ............................................................ 4  Outline Dimensions ..........................................................................9  ESD Caution .................................................................................. 4  ADXL78 Ordering Guide .....................E........................................9  Pin Configuration and Function Descriptions ............................. 5  Automotive Products ....................................................................9  Theory of Operation ........................................................................ 7  T REVISION HISTORY 7/10—Rev. A to Rev. B E Updated Format ................................................................. Universal Change to Features Section ............................................................. 1 Updated Outline Dimensions ......................................................... 9 L Changes to Ordering Guide ............................................................ 9 Added Automotive Products Section ............................................ 9 O 5/05—Rev. 0 to Rev. A S B O Rev. B | Page 2 of 12

ADXL78 SPECIFICATIONS1 At T = −40°C to +105°C, 5.0 V dc ± 5%, acceleration = 0 g, unless otherwise noted. A Table 1. Model No. AD22279 Model No. AD22280 Model No. AD22281 Parameter Conditions Min Typ Max Min Typ Max Min Typ Max Unit SENSOR Output Full-Scale Range I ≤ ±100 μA 37 55 70 g OUT Nonlinearity 0.2 2 0.2 2 0.2 2 % Package Alignment Error 1 1 E1 Degree Cross-Axis Sensitivity −5 +5 −5 +5 −5 +5 % Resonant Frequency 24 24 24 kHz Sensitivity, Ratiometric V = 5 V, 100 Hz 52.25 55 57.75 36.1 38 39.9 25.65 27 28.35 mV/g DD T (Over Temperature) OFFSET Zero-g Output Voltage V − V /2, −200 +200 −150 +150 −150 +150 mV OUT DD (Over Temperature)2 VDD = 5 V E NOISE Noise Density 10 Hz − 400 Hz, 1.1 3 1.4 3 1.8 3.5 mg/√Hz 5 V L Clock Noise 5 5 5 mV p-p FREQUENCY RESPONSE 2-pole Bessel −3 dB Frequency 360 400 440 360 400 440 360 400 440 Hz −3 dB Frequency Drift 25°C to 2 O 2 2 Hz T or T MIN MAX SELF-TEST Output Change V = 5 V 440 550 660 304 380 456 216 270 324 mV DD (Cube vs. V )3 DD S Logic Input High V = 5 V 3.5 3.5 3.5 V DD Logic Input Low V = 5 V 1 1 1 V DD Input Resistance Pull-down 30 50 30 50 30 50 kΩ resistor to GBND OUTPUT AMPLIFIER Output Voltage Swing I = ±400 μA 0.25 V − 0.25 0.25 V − 0.25 0.25 V − 0.25 V OUT DD DD DD Capacitive Load Drive 1000 1000 1000 pF PREFILTER HEADROOM O 280 400 560 g CFSR @ 400 kHz 5 4 3 V/V POWER SUPPLY (V ) 4.75 5.25 4.75 5.25 4.75 5.25 V DD Functional Range 3.5 6 3.5 6 3.5 6 V Quiescent Supply Current V = 5 V 1.3 2 1.3 2 1.3 2 mA DD TEMPERATURE RANGE −40 +105 −40 +105 −40 +105 °C 1 All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed. 2 Zero g output is ratiometric. 3 Self-test output at VDD = (Self-Test Output at 5 V) × (VDD/5 V)3. Rev. B | Page 3 of 12

ADXL78 ABSOLUTE MAXIMUM RATINGS Table 2. Stresses above those listed under Absolute Maximum Ratings Parameter Rating may cause permanent damage to the device. This is a stress Acceleration (Any Axis, Unpowered) 4000 g rating only; functional operation of the device at these or any Acceleration (Any Axis, Powered) 4000 g other conditions above those indicated in the operational V −0.3 V to +7.0 V S section of this specification is not implied. Exposure to absolute All Other Pins (COM − 0.3 V) to maximum rating conditions for extended periods may affect (V + 0.3 V) S device reliability. E Output Short-Circuit Duration Indefinite (Any Pin to Common) ESD CAUTION Operating Temperature Range −65°C to +150°C Storage Temperature −65°C to +150°C T E L O S B O Rev. B | Page 4 of 12

ADXL78 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS VDD2 8 NC 1 7 VDD ADXL78 NC 2 TOP VIEW 6 XOUT (Not to Scale) COM 3 5 NC 4 E NC = NO CONNESCTT 05368-002 Figure 2. Pin Configuration T Table 3. Pin Function Descriptions Pin No. Mnemonic Description E 1 NC Do Not Connect 2 NC Do Not Connect 3 COM Common 4 ST LSelf-Test 5 NC Do Not Connect 6 X X Channel Output OUT 7 VDD O 3.5 V to 6 V 8 V 3.5 V to 6 V DD2 S B O Rev. B | Page 5 of 12

ADXL78 CRITICAL ZONE TP tP TL TO TP RAMP-UP URETL TSMAX tL T A ER TSMIN P M E T t PREHSEAT RAMP-DOWN 05368-003 E t25°C TO PEAK TIME Figure 3. Recommended Soldering Profile T Table 4. Recommended Soldering Profile Profile Feature Sn63/Pb37 Pb-Free E AVERAGE RAMP RATE (T TO T) 3°C/s max 3°C/s max L P PREHEAT Minimum Temperature (T ) 100°C 150°C SMIN Maximum Temperature (T ) 15L0°C 200°C SMAX TIME (T TO T ), t 60 s − 120 s 60 s − 150 s SMIN SMAX S T TO T SMAX L Ramp-Up Rate O 3°C/s 3°C/s TIME MAINTAINED ABOVE LIQUIDOUS (T) L Liquidous Temperature (T) 183°C 217°C L Time (t) 60 s − 150 s 60 s − 150 s L PEAK TEMPERATURE (TP) S 240°C + 0°C/−5°C 260°C + 0°C/−5°C TIME WITHIN 5°C OF ACTUAL PEAK TEMPERATURE (t) 10 s − 30 s 20 s − 40 s P RAMP-DOWN RATE 6°C/s max 6°C/s max TIME 25°C TO PEAK TEMPERATURE 6 min max 8 min max B PIN 8 O XXXXX XXXX XOUT = 2.462V 22280 XOUT = 2.500V XXXXXXXXX 22280 22280 XXXXXXXXX XOUT = 2.500V 08222 XXXX XOUT = 2.538V XXXXX XOUT = 2.500V EARTH'S SURFACE 05368-004 Figure 4. Output Response vs. Orientation Rev. B | Page 6 of 12

ADXL78 THEORY OF OPERATION The ADXL78 provides a fully differential sensor structure and ANCHOR circuit path, resulting in the industry’s highest resistance to EMI/RFI effects. This latest generation uses electrical feedback MOVABLE with zero-force feedback for improved accuracy and stability. PLATE FRAME CAPACITORS The sensor resonant frequency is significantly higher than the UNIT signal bandwidth set by the on-chip filter, avoiding the signal TION SENCSEINLGL FPILXAETDES analysis problems caused by resonant peaks near the signal A R E bandwidth. L CE UNIT Figure 5 is a simplified view of one of the differential sensor AC MOVING E FCOERLLCING PLATE elements. Each sensor includes several differential capacitor unit cells. Each cell is composed of fixed plates attached tDoi sthpela scuebmsetrnatt eo fa tnhde mfroamvaeb lceh palnagteess athttea cdhifefder teon tthiael fcraapmacei.t ance, T ANCHOR 05368-005 which is measured by the on-chip circuitry. Figure 5. Simplified View of Sensor Under Acceleration Complementary 400 kHz square waves drive the fixed plates. E Electrical feedback adjusts the amplitudes of the square waves such that the ac signal on the moving plates is 0. The feedback signal is linearly proportional to the applied acceleration. This unique feedback technique ensures that there is no net L electrostatic force applied to the sensor. The differential feedback control signal is also applied to the input of the filter, where it is filtered and converted to a single-ended signal. O S B O Rev. B | Page 7 of 12

ADXL78 APPLICATIONS POWER SUPPLY DECOUPLING If the difference frequency is outside of the signal bandwidth, the filter attenuates it. However, both the power supply clock For most applications, a single 0.1 μF capacitor, C , adequately DC and the accelerometer clock may vary with time or temperature, decouples the accelerometer from noise on the power supply. which can cause the interference signal to appear in the output However, in some cases, particularly where noise is present at filter bandwidth. the 400 kHz internal clock frequency (or any harmonic The ADXL78 addresses this issue in two ways. First, the high thereof), noise on the supply can cause interference on the clock frequency eases the task of choosing a power supply clock ADXL78’s output. If additional decoupling is needed, a 50 Ω (or frequency such that the difference between it and the accelero- smaller) resistor or ferrite bead can be inserted in the supply meter clock remains well outside of the fEilter bandwidth. line. Additionally, a larger bulk bypass capacitor (in the 1 μF to Second, the ADXL78 is the only micromachined accelerometer 4.7 μF range) can be added in parallel to C . DC to have a fully differential signal path, including differential SELF-TEST sensors. The differential sensors eliminate most of the power T The fixed fingers in the forcing cells are normally kept at the supply noise before it reaches the demodulator. Good high same potential as that of the movable frame. When the self-test frequency supply bypassing, such as a ceramic capacitor close to digital input is activated, the voltage on the fixed fingers on one the supply pins, also minimizes the amount of interference. E side of the moving plate in the forcing cells is changed. This The clock frequency supply response (CFSR) is the ratio of the creates an attractive electrostatic force, which causes the frame response at V to the noise on the power supply near the OUT to move toward those fixed fingers. The entire signal channel is accelerometer clock frequency. A CFSR of 3 means that the active; therefore, the sensor displacement causes a change in signal aLt V is 3× the amplitude of an excitation signal at V OUT DD V . The ADXL78 self-test function is a comprehensive OUT near the accelerometer internal clock frequency. This is method of verifying the operation of the accelerometer. analogous to the power supply response, except that the Because electrostatic force is independent of the polarity of the Ostimulus and the response are at different frequencies. The voltage across capacitor plates, a positive voltage is applied in ADXL78’s CFSR is 10× better than a typical single-ended half of the forcing cells, and its complement in the other half of accelerometer system. the forcing cells. Activating self-test causes a step function force SIGNAL DISTORTION to be applied to the sensor, while the capacitive coupling term is S Signals from crashes and other events may contain high canceled. The ADXL78 has improved self-test functionality, amplitude, high frequency components. These components including excellent transient response and high speed switching contain very little useful information and are reduced by the capabilities. Arbitrary force waveforms can be applied to the sensor by modulating the self-test input, suchB as test signals to 2-pole Bessel filter at the output of the accelerometer. However, if the signal saturates at any point, the accelerometer output measure the system frequency response or even crash signals to does not look like a filtered version of the acceleration signal. verify algorithms within the limits of the self-test swing. The signal may saturate anywhere before the filter. For example, The ST pin should never be exposed to voltages greater than O if the resonant frequency of the sensor is low, the displacement V + 0.3 V. If this cannot be guaranteed due to the system S per unit acceleration is high. The sensor may reach the design (for instance, if there are multiple supply voltages), then mechanical limit of travel if the applied acceleration is high a low V clamping diode between ST and V is recommended. F S enough. This can be remedied by locating the accelerometer CLOCK FREQUENCY SUPPLY RESPONSE where it does not see high values of acceleration, and by using a In any clocked system, power supply noise near the clock higher resonant frequency sensor such as the ADXL78. frequency may have consequences at other frequencies. An Also, the electronics may saturate in an overload condition internal clock typically controls the sensor excitation and the between the sensor output and the filter input. Ensuring that signal demodulator for micromachined accelerometers. the internal circuit nodes operate linearly to at least several If the power supply contains high frequency spikes, they may be times the full-scale acceleration value can minimize electrical demodulated and interpreted as an acceleration signal. A signal saturation. The ADXL78’s circuits are linear to approximately appears as the difference between the noise frequency and the 8× full scale. demodulator frequency. If the power supply spikes are 100 Hz away from the demodulator clock, there is an output term at 100 Hz. If the power supply clock is at exactly the same frequency as the accelerometer clock, the term appears as an offset. Rev. B | Page 8 of 12

ADXL78 OUTLINE DIMENSIONS 0.030 (PLATINGOPTION1, 0.025 SEEDETAILA FOROPTION2) 0.203 0.087 0.054 0.020 0.028 0.197SQ 0.020 0.078 0.050 0.020DIA 0.193 0.015 0.069 0.046 0.012 0.010 (R4PLCS) 7 1 0.180 0.106 0.177SQ 0.075REF 0.100 0.174 R0.008 0.094 (8PLCS) E 5 3 R0.008 TOPVIEW 0.008 BOTTOMVIEW (4PLCS) 0.006 0.077 0.004 0.070 0.019SQ 0.063 (ODPETTIAOILNA2) T 05-21-2010-D Figure 6. 8-Terminal Ceramic Leadless Chip Carrier [LCC] (E-8-1) E Dimensions shown in inches ADXL78 ORDERING GUIDE Parts L per Measurement Specified Temperature Package Model1, 2, 3 Reel Range Voltage (V) Range Package Description Option AD22279-A-R2 250 ±35 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 AD22279-A 3,000 ±35 g 5 −O40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 ADW22279ZC 3,000 ±35 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 ADW22279ZC-RL7 250 ±35 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 AD22280-R2 250 ±50 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 AD22280 3,000 ±50 g 5 S −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 ADW22280ZC 3,000 ±50 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 ADW22280ZC-RL7 250 ±50 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 AD22281-R2 250 ±70 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 B AD22281 3,000 ±70 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 ADW22281ZC 3,000 ±70 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 ADW22281ZC-RL7 250 ±70 g 5 −40°C to +105°C 8-Terminal Ceramic Leadless Chip Carrier E-8-1 O 1 All models are on tape and reel and are RoHS compliant parts. 2 Z = RoHS Compliant Part. 3 W = Qualified for Automotive Applications. AUTOMOTIVE PRODUCTS The ADW22279, ADW22280, and ADW22281 models are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. Note that these automotive models may have specifications that differ from the commercial models; therefore, designers should review the Specifications section of this data sheet carefully. Only the automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific Automotive Reliability reports for these models. Rev. B | Page 9 of 12

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ADXL78 NOTES E T E L O S B O ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05368-0-7/10(B) Rev. B | Page 12 of 12