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Single-Axis, High-g, iMEMS(R) Accelerometers ADXL193
FEATURES
Complete acceleration measurement system on a single monolithic IC Available in 120 g or 250 g output full-scale ranges Full differential sensor and circuitry for high resistance to EMI/RFI Environmentally robust packaging Complete mechanical and electrical self-test on digital command Output ratiometric to supply Sensitive axes in the plane of the chip High linearity (0.2% of full scale) Frequency response down to dc Low noise Low power consumption (1.5 mA) Tight sensitivity tolerance and 0 g offset capability Largest available prefilter clipping headroom 400 Hz, 2-pole Bessel filter Single-supply operation Compatible with Sn/Pb and Pb-free solder processes
GENERAL DESCRIPTION
The ADXL193 is a low power, complete single-axis accelerometer with signal conditioned voltage outputs that are all on a single monolithic IC. This product measures acceleration with a full-scale range of 120 g or 250 g (minimum). It can also measure both dynamic acceleration (vibration) and static acceleration (gravity). The ADXL193 is a fourth-generation surface micromachined iMEMS(R) accelerometer from ADI with enhanced performance and lower cost. Designed for use in front and side impact airbag applications, this product also provides a complete costeffective solution useful for a wide variety of other applications. The ADXL193 is temperature stable and accurate over the automotive temperature range, with a self-test feature that fully exercises all the mechanical and electrical elements of the sensor with a digital signal applied to a single pin. The ADXL193 is available in a 5 mm x 5 mm x 2 mm, 8-terminal ceramic LCC package.
APPLICATIONS
Vibration monitoring and control Vehicle collision sensing Shock detection
FUNCTIONAL BLOCK DIAGRAM
VS
ADXL193
VDD VDD2 400Hz BESSEL FILTER TIMING GENERATOR
EXC
DIFFERENTIAL SENSOR
DEMOD AMP
XOUT
SELF-TEST
Figure 1.
Rev. A 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)2005 Analog Devices, Inc. All rights reserved.
05366-001
ADXL193 TABLE OF CONTENTS
Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 ESD Caution.................................................................................. 4 Pin Configuration and Function Descriptions............................. 5 Theory of Operation ........................................................................ 7 Applications....................................................................................... 8 Power Supply Decoupling ............................................................8 Self-Test ..........................................................................................8 Clock Frequency Supply Response .............................................8 Signal Distortion ...........................................................................8 Outline Dimensions ..........................................................................9 Ordering Guide .............................................................................9
REVISION HISTORY
5/05--Rev. 0 to Rev. A
Rev. A | Page 2 of 12
ADXL193 SPECIFICATIONS 1
At TA = -40C to +105C, 5.0 V dc 5%, acceleration = 0 g; unless otherwise noted. Table 1.
Parameter SENSOR Output Full-Scale Range Nonlinearity Package Alignment Error Cross-Axis Sensitivity Resonant Frequency Sensitivity, Ratiometric (Over Temperature) OFFSET Zero-g Output Voltage (Over Temperature) 2 NOISE Noise Density Clock Noise FREQUENCY RESPONSE -3 dB Frequency -3 dB Frequency Drift SELF-TEST Output Change (Cube vs. VDD) 3 Logic Input High Logic Input Low Input Resistance OUTPUT AMPLIFIER Output Voltage Swing Capacitive Load Drive PREFILTER HEADROOM CFSR @ 400 kHz POWER SUPPLY (VDD) Functional Range Quiescent Supply Current TEMPERATURE RANGE
1 2 3
Conditions IOUT 100 A
Model No. AD22282 Min Typ Max 120 0.2 1 -5 24 18 2 +5 18.9
Model No. AD22283 Min Typ Max 250 0.2 1 -5 7.6 24 8 2 +5 8.4
Unit g % Degree % kHz mV/g
VDD = 5 V, 100 Hz
17.1
VOUT - VDD/2, VDD = 5 V
-125
+125
-100
+100
mV
10 Hz - 400 Hz, 5 V Two-pole Bessel 360 25C to TMIN or TMAX VDD = 5 V VDD = 5 V VDD = 5 V Pull-down resistor to GND IOUT = 400 A 400 3.5
3 5 400 2 500
10
5 5 360 400 2 250
15
mg/Hz mV p-p Hz Hz mV V V k V pF g V/V V V mA C
440
440
600
200 3.5
300
1 30 0.25 1000 800 2 4.75 3.5 5.25 6 2 +125 4.75 3.5 1.5 -40 50 VDD - 0.25 30 0.25 1000 1400 1.5 50
1
VDD - 0.25
VDD = 5 V -40
1.5
5.25 6 2 +125
All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed. Zero g output is ratiometric. Self-test output at VDD = (Self-Test Output at 5 V) x (VDD/5 V)3.
Rev. A | Page 3 of 12
ADXL193 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Acceleration (Any Axis, Unpowered) Acceleration (Any Axis, Powered) VS All Other Pins Output Short-Circuit Duration (Any Pin to Common) Operating Temperature Range Storage Temperature Rating 4,000 g 4,000 g -0.3 V to +7.0 V (COM - 0.3 V) to (VS + 0.3 V) Indefinite -65C to +150C -65C to +150C
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.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. A | Page 4 of 12
ADXL193 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
VDD2
8
NC 1 NC 2 COM 3
4
7
VDD XOUT NC
ADXL193
TOP VIEW (Not to Scale)
6 5
ST NC = NO CONNECT
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 Mnemonic NC NC COM ST NC XOUT VDD VDD2 Description Do Not Connect Do Not Connect Common Self-Test Do Not Connect X Channel Output 3.5 V to 6 V 3.5 V to 6 V
Rev. A | Page 5 of 12
05366-002
ADXL193
CRITICAL ZONE TL TO TP
TP RAMP-UP
TEMPERATURE
tP
TL
TSMAX TSMIN
tL
tS
PREHEAT
RAMP-DOWN
05366-003
t25C TO PEAK
TIME
Figure 3. Recommended Soldering Profile
Table 4. Recommended Soldering Profile
Profile Feature AVERAGE RAMP RATE (TL TO TP) PREHEAT Minimum Temperature (TSMIN) Maximum Temperature (TSMAX) TIME (TSMIN TO TSMAX), tS TSMAX TO TL Ramp-Up Rate 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 Sn63/Pb37 3C/s max 100C 150C 60 s - 120 s 3C/s 183C 60 s - 150 s 240C + 0C/-5C 10 s - 30 s 6C/s max 6 min max Pb-Free 3C/s max 150C 200C 60 s - 150 s 3C/s 217C 60 s - 150 s 260C + 0C/-5C 20 s - 40 s 6C/s max 8 min max
PIN 8
XXXXX XXXX 22282
XOUT = 2.482V
XXXXX XXXX
XXXXX XXXX
22282
22282
XOUT = 2.500V
XOUT = 2.500V
EARTH'S SURFACE
Figure 4. Output Response vs. Orientation
Rev. A | Page 6 of 12
05366-004
XXXXX XXXX
22282 XOUT = 2.518V XOUT = 2.500V
ADXL193 THEORY OF OPERATION
The ADXL193 provides a fully differential sensor structure and circuit path, resulting in the industry's highest resistance to EMI/RFI effects. This latest generation uses electrical feedback with zero-force feedback for improved accuracy and stability. The sensor resonant frequency is significantly higher than the signal bandwidth set by the on-chip filter, avoiding the signal analysis problems caused by resonant peaks near the signal bandwidth. Figure 5 is a simplified view of one of the differential sensor elements. Each sensor includes several differential capacitor unit cells. Each cell is composed of fixed plates attached to the substrate and movable plates attached to the frame. Displacement of the frame changes the differential capacitance, which is measured by the on-chip circuitry. Complementary 400 kHz square waves drive the fixed plates. 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 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.
ANCHOR MOVABLE FRAME PLATE CAPACITORS
ACCELERATION
UNIT SENSING CELL
FIXED PLATES
MOVING PLATE
UNIT FORCING CELL
ANCHOR
Figure 5. Simplified View of Sensor Under Acceleration
Rev. A | Page 7 of 12
05366-005
ADXL193 APPLICATIONS
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 400 kHz internal clock frequency (or any harmonic thereof), noise on the supply can cause interference on the ADXL193's output. If additional decoupling is needed, a 50 (or smaller) resistor or ferrite bead can be inserted in the supply line. Additionally, a larger bulk bypass capacitor (in the 1 F to 4.7 F range) can be added in parallel to CDC. If the difference frequency is outside of the signal bandwidth, the filter attenuates it. However, both the power supply clock and the accelerometer clock may vary with time or temperature, which can cause the interference signal to appear in the output filter bandwidth. The ADXL193 addresses this issue in two ways. First, the high clock frequency eases the task of choosing a power supply clock frequency such that the difference between it and the accelerometer clock remains well outside of the filter bandwidth. Second, the ADXL193 is the only micromachined accelerometer to have a fully differential signal path, including differential sensors. The differential sensors eliminate most of the power supply noise before it reaches the demodulator. Good high frequency supply bypassing, such as a ceramic capacitor close to the supply pins, also minimizes the amount of interference. The clock frequency supply response (CFSR) is the ratio of the response at VOUT to the noise on the power supply near the accelerometer clock frequency. A CFSR of 3 means that the signal at VOUT is 3x the amplitude of an excitation signal at VDD near the accelerometer internal clock frequency. This is analogous to the power supply response, except that the stimulus and the response are at different frequencies. The ADXL193's CFSR is 10x better than a typical single-ended accelerometer system.
SELF-TEST
The fixed fingers in the forcing cells are normally kept at the same potential as that of the movable frame. When the self-test digital input is activated, the voltage on the fixed fingers on one side of the moving plate in the forcing cells is changed. This creates an attractive electrostatic force, which causes the frame to move toward those fixed fingers. The entire signal channel is active; therefore, the sensor displacement causes a change in VOUT. The ADXL193's self-test function is a comprehensive method of verifying the operation of the accelerometer. Because electrostatic force is independent of the polarity of the voltage across capacitor plates, a positive voltage is applied in half of the forcing cells, and its complement in the other half of the forcing cells. Activating self-test causes a step function force to be applied to the sensor, while the capacitive coupling term is canceled. The ADXL193 has improved self-test functionality, including excellent transient response and high speed switching capability. Arbitrary force waveforms can be applied to the sensor by modulating the self-test input, such as test signals to measure the system frequency response, or even crash signals to verify algorithms within the limits of the self-test swing. The ST pin should never be exposed to voltages greater than VS + 0.3 V. If this cannot be guaranteed due to the system design (for instance, if there are multiple supply voltages), then a low VF clamping diode between ST and VS is recommended.
SIGNAL DISTORTION
Signals from crashes and other events may contain high amplitude, high frequency components. These components contain very little useful information and are reduced by the 2-pole Bessel filter at the output of the accelerometer. However, if the signal saturates at any point, the accelerometer output does not look like a filtered version of the acceleration signal. The signal may saturate anywhere before the filter. For example, if the resonant frequency of the sensor is low, the displacement per unit acceleration is high. The sensor may reach the mechanical limit of travel if the applied acceleration is high enough. This can be remedied by locating the accelerometer where it does not see high values of acceleration and by using a higher resonant frequency sensor, such as the ADXL193. Also, the electronics may saturate in an overload condition between the sensor output and the filter input. Ensuring that internal circuit nodes operate linearly to at least several times the full-scale acceleration value can minimize electrical saturation. The ADXL193 circuit is linear to approximately 8x full scale.
CLOCK FREQUENCY SUPPLY RESPONSE
In any clocked system, power supply noise near the clock frequency may have consequences at other frequencies. An internal clock typically controls the sensor excitation and the signal demodulator for micromachined accelerometers. If the power supply contains high frequency spikes, they may be demodulated and interpreted as an acceleration signal. A signal appears as the difference between the noise frequency and the 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. A | Page 8 of 12
ADXL193 OUTLINE DIMENSIONS
5.00 SQ 1.78 1.27 4.50 SQ
TOP VIEW
1.27
7 1
0.50 DIAMETER 1.90 2.50
1.27 R 0.38 0.20 R 0.20
5
3
0.64 2.50
0.38 DIAMETER
BOTTOM VIEW
Figure 6. 8-Terminal Ceramic Leadless Chip Carrier [LCC] (E-8) Dimensions shown in millimeters
ADXL193 ORDERING GUIDE
Model 1 AD22282-A-R2 AD22282-A AD22283-B-R2 AD22283-B
1
Parts per Reel 250 3000 250 3000
Measurement Range 120 g 120 g 250 g 250 g
Specified Voltage (V) 5 5 5 5
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package Description 8-Terminal Ceramic Leadless Chip Carrier 8-Terminal Ceramic Leadless Chip Carrier 8-Terminal Ceramic Leadless Chip Carrier 8-Terminal Ceramic Leadless Chip Carrier
Package Option E-8 E-8 E-8 E-8
All models are on tape and reel and are Pb-free parts.
Rev. A | Page 9 of 12
ADXL193 NOTES
Rev. A | Page 10 of 12
ADXL193 NOTES
Rev. A | Page 11 of 12
ADXL193 NOTES
(c)2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05366-0-5/05(A)
Rev. A | Page 12 of 12

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