ADXL212AEZ

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Precision ±2 g Dual Axis, PWM Output Accelerometer ADXL212 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. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2011 Analog Devices, Inc. All rights reserved.

FEATURES

Dual axis accelerometer on a single IC chip 5 mm × 5 mm × 2 mm LCC package 5 mg resolution at 60 Hz Low power: 700 μA at V S = 5 V (typical) High zero g bias stability High sensitivity accuracy Pulse width modulated digital outputs X- and Y-axis aligned to within 0.1° (typical) Bandwidth adjustment with a single capacitor Single-supply operation 3500 g shock survival

APPLICATIONS

Vehicle dynamic control (VDC)/electronic stability program (ESP) systems Electronic chassis control Electronic braking Data projectors Navigation Platform stabilization/leveling Alarms and motion detectors High accuracy, 2-axis tilt sensing GENERAL DESCRIPTION The ADXL212 is a high precision, low power, complete dual axis accelerometer with signal conditioned, duty cycle modulated outputs, all on a single monolithic IC. The ADXL212 measures acceleration with a full-scale range of ±2 g (typical). The ADXL212 measures both dynamic acceleration (such as vibration) and static acceleration (such as gravity). The outputs are digital signals whose duty cycles (ratio of pulse width to period) are proportional to acceleration (12.5%/g) in each of the two sensitive axes. The duty cycle outputs can be directly measured by a microcontroller without an analog-to- digital converter (ADC) or glue logic. The output period is adjustable from 0.5 ms to 10 ms via a single resistor (R SET). The typical noise floor is 500 μg/√Hz, allowing signals below 5 mg (0.3° of inclination) to be resolved in tilt sensing applica- tions using narrow bandwidths (<60 Hz). The user selects the bandwidth of the accelerometer using Capacitors CX and CY at the XFILT and YFILT pins. Bandwidths of 0.5 Hz to 500 Hz can be selected to suit the application. The ADXL212 is available in a 5 mm × 5 mm × 2 mm, 8-lead hermetic LCC package. FUNCTIONAL BLOCK DIAGRAM 09804-001 ADXL212 SENSOR 32kΩ 32kΩ +VS OUTPUT AMP OUTPUT AMP DCM COM ST XFILT YFILTVS CDC CX DEMOD CY YOUT XOUT RSET AC AMP 0g = 50% DUTY CYCLE t2(sec) = RSET/125MΩ PWM OUTPUT WAVEFORM SAMPLE Figure 1.

Rev. 0 | Page 2 of 12 TABLE OF CONTENTS Design Trade-Offs for Selecting Filter Characteristics: Noise Using the ADXL212 with Operating Voltages Other Than 5 V

REVISION HISTORY

5/11—Revision 0: Initial Version

Rev. 0 | Page 3 of 12 SPECIFICATIONS TA = –40°C to +85°C, VS = 5 V , CX = CY = 0.1 μF, acceleration = 0 g, unless otherwise noted. All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed. Table 1. Parameter Test Conditions/Comments Min Typ Max Unit SENSOR INPUT Each axis Measurement Range1 ±1.5 ±2 g Nonlinearity Best fit straight line ±0.2 % of FS Package Alignment Error ±1 Degrees Alignment Error X sensor to Y sensor ±0.01 Degrees Cross Axis Sensitivity ±2 % SENSITIVITY (RATIOMETRIC)2 Each axis Sensitivity at XOUT, YOUT V S = 5 V 10 12.5 15 %/g Sensitivity Change Due to Temperature3 V S = 5 V ±0.5 % ZERO g BIAS LEVEL (RATIOMETRIC) Each axis 0 g Duty Cycle at XOUT, YOUT 25 50 75 % Initial 0 g Output Deviation from Ideal TA = 25°C ±2 % 0 g Duty Cycle vs. Supply 1.0 4.0 %/V 0 g Offset vs. Temperature ±2 mg/°C NOISE PERFORMANCE Noise Density TA = 25°C 500 1000 μg/√Hz rms FREQUENCY RESPONSE4 3 dB Bandwidth5 500 Hz CX, CY Range5 0.002 4.7 μF Sensor Resonant Frequency 5.5 kHz SELF TEST6 Duty Cycle Change Self test (ST) pin: pulled low (0) to high (1) 10 % DUTY CYCLE OUTPUT STAGE fSET7 R SET = 125 kΩ 1 kHz fSET7 Tolerance RSET = 125 kΩ 0.7 1.3 kHz Voltage Levels High I = 25 μA VS − 0.2 V Low I = 25 μA 200 mV t2 Drift vs. Temperature ±35 ppm/°C Rise/Fall Time 200 ns POWER SUPPLY Operating Voltage Range 3.0 5.25 V Specified Performance 4.75 5.25 V Quiescent Supply Current 0.7 1.1 mA Turn-On Time8 19 ms TEMPERATURE RANGE Specified Performance −40 +85 °C 1 Guaranteed by measurement of initial offset and sensitivity. 2 Sensitivity varies with VS. At VS = 3 V, sensitivity is typically 7.5%/g. 3 Defined as the output change from ambient-to-maximum temperature or ambient-to-minimum temperature. 4 Actual frequency response is controlled by a user supplied external capacitor (CX, CY). 6 Self test response changes with VS. At VS = 3 V, self test output is typically 6%.

7 The value of fSET is defined by the following equation:

fSET = 8 Larger values of CX, CY increase turn-on time. Turn-on time is approximately 160 × CX or CY + 3, where CX, CY are in μF, and the resulting turn-on time is in ms.

soldered in a circuit board for surface-mount packages. Table 3. Thermal Resistance Figure 2. Recommended Soldering Profile Table 4. Soldering Profile

Figure 3. Pin Configuration Table 5. Pin Function Descriptions 2 T2 Frequency Set. Connect the RSET resistor to ground. See the Theory of Operation section for details. 6 Y FILT Y Channel Filter Pin. 7 X FILT X Channel Filter Pin. 8 V S Voltage Supply. 3 V to 5.25 V.

decouples the accelerometer from noise on the power supply. smaller) resistor or ferrite beads in the supply line of the ADXL212. Table 6. Filter Capacitor Selection, CX and CY open circuit, or it can be connected to ground in normal use. diode between ST and VS is recommended. filter capacitors at XFILT and YFILT. to the lowest frequency needed by the application. Table 7. Estimation of Peak-to-Peak Noise noise output of the ADXL212 for various CX and CY values. Table 8. Filter Capacitor Selection (CX, CY)

Rev. 0 | Page 11 of 12 USING THE ADXL212 WITH OPERATING VOLTAGES OTHER THAN 5 V The ADXL212 is tested and specified at VS = 5 V; however, it can be powered with VS as low as 3 V or as high as 5.25 V . Some performance parameters change as the supply voltage varies. The ADXL212 sensitivity varies proportionally to supply voltage. At VS = 3 V , the sensitivity is typically 7.5%/g. The zero g bias output is ratiometric to supply voltage; therefore, the zero g output is nominally equal to 50% at all supply voltages. Self test response in g is roughly proportional to the square of the supply voltage. Therefore, at VS = 3 V , the self test response is equivalent to approximately 270 mg (typical), or 6%. The supply current decreases as the supply voltage decreases. Typical current consumption at VDD = 3 V is 450 μA. USING THE ADXL212 AS A DUAL AXIS TILT SENSOR A common application of the ADXL212 is tilt measurement. An accelerometer uses the force of gravity as an input vector to deter- mine its orientation in space. An accelerometer is most sensitive to tilt when its sensitive axis is perpendicular to the force of gravity, that is, parallel to the surface of the earth. At this orientation, its response to changes in tilt is highest: its output changes nearly 17.5 mg per degree of tilt. When the accelerometer is oriented on axis to gravity, that is, near its +1 g or –1 g reading, the change in output acceleration per degree of tilt is negligible. At 45°, its output changes by 12.2 mg per degree. Dual Axis Tilt Sensor: Converting Acceleration to Tilt When the accelerometer is oriented with both its x-axis and y-axis parallel to the surface of the earth (reading approximately 0 g), it can be used as a dual axis tilt sensor with a roll axis and a pitch axis. The output tilt in degrees is calculated as follows: Pitch = ASIN(AX/1 g) Roll = ASIN(AY/1 g) where AX and AY are accelerations in g, ranging from −1 g to +1 g. Be sure to account for overranges. It is possible for the accelerometers to output a signal greater than ±1 g due to vibration, shock, or other accelerations.

0.075 REF

0.020 DIA

Figure 21. 8-Terminal Ceramic Leadless Chip Carrier [LCC] registered trademarks are the property of their respective owners.