ADXL05

ADXL05_15 AD | Alldatasheet

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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 rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. a 61 g to 65 g Single Chip Accelerometer with Signal Conditioning ADXL05*

FEATURES

Noise Level 12 3 Less than the ADXL50 User Selectable Full Scale from 61 g to 65 g Output Scale Selectable from 200 mV/ g to 1 V/ g Complete Acceleration Measurement System on a Single Chip IC Self Test on Digital Command +5 V Single Supply Operation 1000 g Shock Survival

APPLICATIONS

Low Cost Sensor for Vibration Measurement Tilt Sensing with Faster Response than Electrolytic or Mercury Sensors More Sensitive Alarms and Motion Detectors Affordable Inertial Sensing of Velocity and Position floor is 500 µg/√Hz, (12× less than the ADXL50), allowing sig- nals below 5 milli-g to be resolved. The ADXL05 is a force bal- anced capacitive accelerometer with the capability to measure both ac accelerations (typical of vibration) or dc accelerations (such as inertial force or gravity). Three external capacitors and a +5 volt regulated power supply are all that is required to measure accelerations up to ± 5 g. Three resistors are used to configure the output buffer amplifier to set scale factors from 200 mV/g to 1 V/g. External capacitors may be added to the resistor network to provide 1 or 2 poles of filtering. No addi- tional active components are required to interface directly to most analog to digital converters (ADCs). The device features a TTL compatible self-test function that can electrostatically deflect the sensor beam at any time to verify that the sensor and its electronics are functioning correctly. The ADXL05 is available in a hermetic 10-pin TO-100 metal can, specified over the 0 °C to +70°C commercial, and –40°C to +85°C industrial temperature ranges. Contact factory for avail- ability of automotive grade devices. *Patents pending. © Analog Devices, Inc., 1996 Tel: 617/329-4700 Fax: 617/326-8703 GENERAL DESCRIPTION The ADXL05 is a complete acceleration measurement system on a single monolithic IC. The ADXL05 will measure accelera- tions with full-scale ranges of ± 5 g to ± 1 g or less. Typical noise FUNCTIONAL BLOCK DIAGRAM SENSOR REFERENCE 6 91083215

4 DEMODULATOR

+5V DEMODULATOR CAPACITOR C1 C1COM VPR VIN– R3 VREF OUTPUT +3.4V VOUT SELF-TEST (ST) +1.8V OBSOLETE

ADXL05–SPECIFICATIONS ADXL05J/A Parameter Conditions Min Typ Max Units SENSOR INPUT Measurement Range Guaranteed Full Scale –5 +5 g Nonlinearity Best Fit Straight Line, 5 g FS 0.2 % of FS Alignment Error 1 ± 1 Degrees Transverse Sensitivity 2 ± 2% SENSITIVITY Initial Sensitivity at V PR +25°C 175 200 225 mV/ g Initial Sensitivity at V OUT +25°C, R3/R1 = 5 0.875 1.000 1.125 V/ g Temperature Drift 3 ± 0.5 % of Reading ZERO g BIAS LEVEL at V PR Initial Offset 1.50 1.80 2.10 V vs. Temperature 3 ± 25/40 mV vs. Supply V S = 4.75 V to 5.25 V 10 32 mV/V NOISE PERFORMANCE at V PR Voltage Noise Density BW = 4 Hz to 1 kHz 500 1000 µg/√Hz Noise in 100 Hz Bandwidth 5m g rms Noise in 10 Hz Bandwidth 1.6 m g rms FREQUENCY RESPONSE 3 dB Bandwidth 4 C1 = 0.022 µF (See Figure 9) 1000 1600 Hz 3 dB Bandwidth 4 C1 = 0.010 µF 4 kHz Sensor Resonant Frequency 12 kHz SELF TEST INPUT Output Change at V PR 5 ST Pin from Logic “0” to “1” –0.85 –1.00 –1.15 V Logic “1” Voltage 2.0 V Logic “0” Voltage 0.8 V Input Resistance To Common 50 k Ω +3.4 V REFERENCE Output Voltage 3.350 3.400 3.450 V Output Temperature Drift 3 ± 5m V Power Supply Rejection DC, V S = +4.75 V to +5.25 V 1 10 mV/V Output Current Sourcing 500 µA PREAMPLIFIER OUTPUT Voltage Swing 0.25 V S – 1.4 V Current Output Source or Sink 30 80 µA Capacitive Load Drive 100 pF BUFFER AMPLIFIER Input Offset Voltage 6 Delta from Nominal 1.800 V ± 10 ± 25 mV Input Bias Current 52 0 n A Open-Loop Gain DC 80 dB Unity Gain Bandwidth 200 kHz Output Voltage Swing I OUT = ± 100 µA 0.25 V S – 0.25 V Capacitive Load Drive 1000 pF Power Supply Rejection DC, V S = +4.75 V to +5.25 V 1 10 mV/V POWER SUPPLY Operating Voltage Range 4.75 5.25 V Quiescent Supply Current 8.0 10.0 mA TEMPERATURE RANGE Operating Range J 0 +70 °C Specified Performance A –40 +85 °C Automotive Grade* –40 +125 °C NOTES 1Alignment error is specified as the angle between the true and indicated axis of sensitivity, (see Figure 2). 2Transverse sensitivity is measured with an applied acceleration that is 90 ° from the indicated axis of sensitivity. Transverse sensitivity is specified as the percent of transverse acceleration that appears at the V PR output. This is the algebraic sum of the alignment and the inherent sensor sensitivity errors, (see Figure 2). 3Specification refers to the maximum change in parameter from its initial at +25 °C to its worst case value at T MIN to TMAX. 4Frequency at which response is 3 dB down from dc response assuming an exact C1 value is used. Maximum recommended BW is 6 kHz using a 0.010 µF capacitor, refer to Figure 9. 5Applying logic high to the self-test input has the effect of applying an acceleration of –5 g to the ADXL05. 6Input offset voltage is defined as the output voltage differential from 1.800 V when the amplifier is connected as a follower. The voltage at this pin has a temperature drift proportional to that of the 3.4 V reference. *Contact factory for availability of automotive grade devices. All min and max specifications are guaranteed. Typical specifications are not tested or guaranteed. Specifications subject to change without notice. (TA = TMIN to TMAX, TA = +258C for J Grade Only, V S = +5 V, @ Acceleration = 0 g, unless otherwise noted) –2– REV. B OBSOLETE

0.1µF +5V VOUT 0.022µF +3.4V REF COM 1.8V 6 8 0.022µF PRE-AMP VPR R3VIN– ADXL05 NOMINAL VALUES: R1 = 49.9kΩ R3 = 100kΩ (G=2) R2 = 255kΩ (G=2) DC COUPLED CONNECTION (62 g Full Scale) (@ VOUT Terminal (Pin 9), unless otherwise noted. 0 g Bias Level = +2.5 V, C1 = 0.022 mF, R2 = 2.57 R3) ADXL05J/A Parameter Conditions Min Typ Max Units Buffer Gain G = R3/R1* 2 FULL-SCALE RANGE –2 +2 g SENSITIVITY @ +25°C 350 400 450 mV/ g Temperature Drift T MIN to TMAX ± 0.5 % of Reading ZERO g BIAS LEVEL @ +25 °C 1.75 2.5 3.2 V Temperature Drift +25 °C to TMIN or TMAX ± 50/80 mV FREQUENCY RESPONSE dc 1000 Hz *Note: Resistor tolerance will affect system accuracy. Use of ± 1% (or better) metal film resistors is recommended. AC COUPLED CONNECTION (61.5 g Full Scale) (@ VOUT Terminal (Pin 9), unless otherwise noted. 0 g Bias Level = +2.5 V, C1 = 0.022 mF, R2 = 2.57 R3 ADXL05J/A Parameter Conditions Min Typ Max Units Buffer Gain G = R3/R1* 5 FULL-SCALE RANGE –1.5 +1.5 g SENSITIVITY @ +25°C 875 1000 1,125 mV/ g Temperature Drift T MIN to TMAX ± 0.5 % of Reading ZERO g BIAS LEVEL @ +25 °C 2.5 V Temperature Drift +25 °C to TMIN or TMAX 2/5 mV FREQUENCY RESPONSE C4 = 3.3 µF, R1 = 49.9 kΩ 1 1000 Hz *Note: Resistor tolerance will affect system accuracy. Use of ± 1% (or better) metal film resistors is recommended. System Performance Specifications–ADXL05 BUFFER AMP 0.1µF +5V VOUT 0.022µF +3.4V REF COM 1.8V 6 8 0.022µF PRE-AMP VPR R3VIN– ADXL05 R1C4 NOMINAL VALUES: R1 = 49.9kΩ R3 = 249kΩ R2 = 640kΩ REV. B –3– OBSOLETE

REV. B–4– Package Characteristics Package uJA uJC Device Weight 10-Pin TO-100 130 °C/W 30 °C/W 5 Grams ORDERING GUIDE Model Temperature Range ADXL05JH 0 °C to +70°C ADXL05AH –40 °C to +85°C ABSOLUTE MAXIMUM RATINGS* Output Short Circuit Duration *Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only; the functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 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 the ADXL05 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. WARNING! ESD SENSITIVE DEVICE Drops onto hard surfaces can cause shocks of greater than 1000 g and exceed the absolute maximum rating of the device. Care should be exercised in handling to avoid damage. PIN DESCRIPTION +5 V The power supply input pin. C2 Connection for an external bypass capacitor (nominally 0.022 µF) used to prevent oscillator switching noise from interfering with other ADXL05 circuitry. Please see the section on component selection. C1 Connections for the demodulator capacitor, nominally 0.022 µF. See the section on component selection for application information. COM The power supply common (or “ground”) connection. VREF Output of the internal 3.4 V voltage reference. ST The digital self-test input. It is both CMOS and TTL compatible. V PR The ADXL05 preamplifier output providing an output voltage of 200 mV per g of acceleration. VOUT Output of the buffer amplifier. VIN– The inverting input of the uncommitted buffer amplifier. CONNECTION DIAGRAM 10-Header (TO-100) AXIS OF SENSITIVITY AXIS OF SENSITIVITY VIN– VOUT VPR ST VREF COM +5V TOP VIEW NOTES: AXIS OF SENSITIVITY IS ALONG A LINE BETWEEN PIN 5 AND THE TAB. THE CASE OF THE METAL CAN PACKAGE IS CONNECTED TO PIN 5 (COMMON). ARROW INDICATES DIRECTION OF POSITIVE ACCELERATION ALONG AXIS OF SENSITIVITY. OBSOLETE

1 MHz square wave: the two square wave amplitudes are equal

Figure 16. A Simplified Diagram of the ADXL05 eration experienced by the sensor. Figure 17. The ADXL05 Sensor Momentarily Responding Figure 18. Functional Block Diagram

0 g position and is a direct measure of the applied acceleration. chip and +3.4 volts for external use. proportional to the sensitivity error, see Self-Test section. around 0 g, and a 3 dB bandwidth of approximately 1.6 kHz. Figure 19. ADXL05 Application Providing an Output Sensitivity of 400 mV/g,

will be increased by a factor of 10 (20 dB). when measuring low g accelerations. cal noise vs. bandwidth characteristic of the ADXL05. Figure 24. Noise Level vs. 3 dB Bandwidth determined by the 1-pole post filter R3, C5.

0 g bias level) should be indicated. Figure 30. Using the Earth’s Gravity to Self-Calibrate the +2.5 V at the buffer output (see Figure 25). simple, low cost circuit can provide substantial power reduction. the absolute accuracy of the measurement. sensitive industrial and commercial applications. acceleration is velocity and the integral of velocity is distance. fewer accelerometers and gyros. double integration of the acceleration signal. math required to correct the sensor. order to provide a velocity output.

REV. B–18– low-pass filtering generally results in smaller capacitance values and better overall performance. It is also a convenient and more precise way to set the system bandwidth. Post filtering allows bandwidth to be controlled accurately by component selection and avoids the ± 40% demodulation tolerance. Note that signal noise is proportional to the square root of the bandwidth of the ADXL05 and may be a consideration in component selection— see section on noise. Care should be taken to reduce or eliminate any leakage paths from the demodulator capacitor pins to common or to the +5 V pin. Even a small imbalance in the leakage paths from these pins will result in offset shifts in the zero- g bias level. As an example, an unbalanced parasitic resistance of 30 M Ω from either de- modulator pin to ground will result in an offset shift at V PR of approximately 50 mV. Conformal coating of PC boards with a high impedance material is recommended to avoid leakage prob- lems due to aging or moisture. MINIMIZING EMI/RFI The architecture of the ADXL05 and its use of synchronous de- modulation make the device immune to most electromagnetic (EMI) and radio frequency (RFI) interference. The use of syn- chronous demodulation allows the circuit to reject all signals ex- cept those at the frequency of the oscillator driving the sensor element. However, the ADXL05 does have a sensitivity to RFI that is within ± 5 kHz of the internal oscillator’s nominal fre- quency of 1 MHz and also to any odd harmonics of this fre- quency. The internal oscillator frequency will exhibit part to part variation in the range of 0.5 MHz to 1.4 MHz. In general the effect is difficult to notice as the interference must match the internal oscillator within ± 5 kHz and must be large in amplitude. For example: a 1 MHz interference signal of 20 mV p-p applied to the +5 V power supply pin will produce a 200 mV p-p signal at the V PR pin if the internal oscillator and interference signals are matched exactly or at odd harmonics. If the same 20 mV interference is applied but 5 kHz above or be- low the internal oscillator’s frequency, the signal level at V PR will only be 20 mV p-p in amplitude. Power supply decoupling, short component leads (especially for capacitors C1 and C2), physically small (surface mount, etc.) components and attention to good grounding practices all help to prevent RFI and EMI problems. Good grounding practices include having separate analog and digital grounds (as well as separate power supplies or very good decoupling) on the printed circuit boards. A single ground line shared by both the digital and analog circuitry can lead to digital pulses (and clock signals) interfering with the sensor’s onboard oscillator. In extreme cases, a low cost radio frequency choke ( ≈10 µH) may be needed in series with the accelerometer’s power supply pin. This, together with the recommended 0.1 µF power supply by- pass capacitor, will form an effective RF filter. The use of an RF choke is preferred over a resistor since any series resistance in the power supply will “unregulate” the device from the supply, degrade its power supply rejection and reduce its supply voltage. output change at V PR. If the ADXL05 is experiencing an acceleration when the self-test is initiated, the V PR output will equal the algebraic sum of the two inputs. The output will stay at the self-test level as long as the ST input remains high and will return to the 0 g level when the ST voltage is removed. A self-test output that varies more than ± 15% from the nominal –1.0 V change indicates a defective beam or a circuit problem such as an open or shorted pin or component. Operating the ADXL05’s buffer amplifier at Gains > 2, to pro- vide full-scale outputs of less than ± 5 g, may cause the self-test output to overdrive the buffer into saturation. The self-test may still be used in the case, but the change in the output must then be monitored at the V PR pin instead of the buffer output. Note that the value of the self-test delta is not an exact indica- tion of the sensitivity (mV/ g) of the ADXL05 and, therefore, may not be used to calibrate the device for sensitivity error. In critical applications, it may be desirable to monitor shifts in the zero-g bias voltage from its initial value. A shift in the 0 g bias level may indicate that the 0 g level has shifted which may warrant an alarm. Power Supply Decoupling The ADXL05 power supply should be decoupled with a 0.1 µF ceramic capacitor from +5 V pin of the ADXL05 to common using very short component leads. For other decoupling consid- erations, see EMI/RFI section. Oscillator Decoupling Capacitor, C2 An oscillator decoupling capacitor, C2, is used to remove

1 MHz switching transients in the sensor excitation signal, and

is required for proper operation of the ADXL05. A ceramic capacitor with a minimum value of 0.022 µF is recommended from the oscillator decoupling capacitor pin to common. Small amounts of capacitor leakage due to a dc resistance greater than 1M Ω will not affect operation (i.e., a high quality capacitor is not needed here). As with the power supply bypass capacitor, very short component leads are recommended. Although 0.022 µF is a good typical value, it may be increased for reasons of convenience, but doing this will not improve the noise perfor- mance of the ADXL05. Demodulator Capacitor, C1 The demodulator capacitor is connected across Pins 2 and 3 to set the bandwidth of the force balance control loop. This capaci- tor may be used to approximately set the bandwidth of the ac- celerometer. A capacitor is always required for proper operation. The frequency response of the ADXL05 exhibits a single pole roll-off response, see Figure 4. A nominal value of 0.022 µF is recommended for C1. In gen- eral, the design bandwidth should be set 40% higher than the minimum desired system bandwidth due to the ± 40% tolerance, to preserve stability C1 should be kept > 0.01 µF. The demodulation capacitor should be a low leakage, low drift ceramic type with an NPO (best) or X7R (good) dielectric. In general, it’s best to use the recommended 0.022 µF capacitor across the demodulator pins and perform any additional low- pass filtering using the buffer amplifier. The use of the buffer for OBSOLETE

–19–REV. B OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 0.160 (4.06) 0.110 (2.79) 0.034 (0.86) 0.027 (0.69) 0.045 (1.14) 0.027 (0.69) 0.115 (2.92) BSC 5 7 0.230 (5.84) BSC REFERENCE PLANE SEATING PLANE 0.335 (8.51) 0.305 (7.75) 0.370 (9.40) 0.335 (8.51) 0.750 (19.05) 0.500 (12.70) 0.045 (1.14) 0.010 (0.25) 0.040 (1.02) MAX 0.185 (4.70) 0.165 (4.19) OBSOLETE

C2028b–5–3/96PRINTED IN U.S.A. –20– OBSOLETE