D2002BL

MXD2002A ETC1 | Alldatasheet

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Technical content

Low Cost, ±10 g Dual Axis Accelerometer with Digital Outputs MXD2002A/B

FEATURES

Dual axis accelerometer fabricated on a monolithic CMOS IC On-chip mixed mode signal processing Resolution better than 6 milli-g 50,000 g shock survival rating

30 Hz bandwidth

2.70V to 5.25V single supply operation Small (5mm x 5mm x 2mm) surface mount package Continuous self test Independently programmable axis (factory special)

APPLICATIONS

Automotive – Vehicle Security/Active Suspension/ABS HED Angle Control/Tilt Sensing Security – Gas Line/Elevator/Fatigue Sensing Office Equipment – Computer Peripherals/PDA’s/Mouse Smart Pens/Cell Phones Gaming – Joystick/RF Interface/Menu Selection/Tilt Sensing White Goods – Spin/Vibration Control Internal Os cillator Sck (opt iona l) CL K Heater Cont rol X a xis Y ax is Factory A djust Offset & G ain LPF LPF Tem perature Sens or Voltage Re ference Vref Do ut X Vd d VdaGn d 2-AXIS SENSO R Do ut Y To ut Contin ous Self T est A/D A/D MXD2002A/B FUNCTIONAL BLOCK DIAGRAM The MXD2002A/B is a very low cost, dual axis accelerometer fabricated on a standard, submicron CMOS process. The MXD2002A/B measures acceleration with a full-scale range of ±10 g. (The MEMSIC accelerometer product line extends from ±1 g to ±10 g with custom versions available above ±10 g.) It can measure both dynamic acceleration (e.g., vibration) and static acceleration (e.g., gravity). The MXD2002A/B design is based on heat convection and requires no solid proof mass. This eliminates stiction and particle problems associated with competitive devices and provides shock survival up to 50,000 g, leading to significantly lower failure rates and lower loss due to handling during assembly. The MXD2002A/B provides a digital output (ref. other MEMSIC data sheets for analog or ratiometric analog outputs). The outputs are digital signals with duty cycles (ratio of pulsewidth to period) that are proportional to acceleration. The duty cycle outputs can be directly interfaced to a micro-processor. Information furnished by MEMSIC is believed to be accurate and reliable. However, no responsibility is assumed by MEMSIC 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 MEMSIC. The typical noise floor is .0015% duty cycle / Hz allowing signals below 6 milli-g to be resolved at 1 Hz bandwidth. The MXD2002A/B is available in a low profile LCC surface mount package (5mm x 5mm x 2mm height). It is hermetically sealed and operational over a -40°C to +105°C temperature range. Due to the standard CMOS structure of the MXD2002A/B, additional circuitry can easily be incorporated into custom versions for high volume applications. Contact the factory for more information. MEMSIC, Inc.

100 Burtt Road, Andover, MA 01810

Tel: 978.623.8188 Fax: 978.623.9945 www.memsic.com MEMSIC MXD2002A/B Rev.E Page 1 of 8 5/15/2004

MEMSIC MXD2002A/B Rev.E Page 2 of 8 5/15/2004 MXD2002A/B SPECIFICATIONS (Measurements @ 25°C, Acceleration = 0 unless otherwise noted, VDD, VDA = 5.0V unless otherwise specified) Parameter Conditions Min MXD2002A/B Typ Max Units SENSOR INPUT Measurement Range1 Each Axis ±10 g Nonlinearity Best fit straight line 1.0 2.0 % of FS Alignment Error2 ±1.0 degrees Transverse Sensitivity3 ±2.0 % SENSITIVITY DOUTX and DOUTY Each Axis @5.0V supply 1.80 2.00 2.20 % Duty Cycle/g Change over Temperature (uncompensated)4 ∆ from 25°C, at –40°C +93 % ∆ from 25°C, at +105°C -47 % Change over Temperature (compensated) 4 ∆ from 25°C, –40°C to +105°C <3.0 % ZERO g BIAS LEVEL 0 g Offset5 Each Axis -0.70 0.00 +0.70 g 0 g Duty Cycle5 48.6 50 51.4 % Duty Cycle 0 g Offset over Temperature ∆ from 25°C ∆ from 25°C, based on 2%/g ±2.0 ±004 mg/°C % / °C NOISE PERFORMANCE Noise Density, % Duty Cycle .0015 0.005 % Duty Cycle/ Hz FREQUENCY RESPONSE 3dB Bandwidth 30 Hz TEMPERATURE OUTPUT Tout Voltage 1.15 1.25 1.35 V Sensitivity 4.6 5.0 5.4 mV/°K VOLTAGE REFERENCE Change over Temperature 0.1 mV/°C Current Drive Capability Source 100 µA SELF TEST Continuous Voltage at DOUTX, DOUTY under Failure @5.0V Supply, output rails to supply voltage 5.0 V Continuous Voltage at DOUTX, DOUTY under Failure @2.7V Supply, output rails to supply voltage 2.7 V DOUTX and DOUTY OUTPUTS Digital Signal of 100 Hz or 400Hz Normal Output Range @5.0V Supply @2.7V Supply 0.1 0.1 4.9 2.6 V V Current Source or sink, @ 2.7V-5.0V supply 100 µA Rise/Fall Time 2.7 to 5.0V Supply 100 110 nSec POWER SUPPLY Operating Voltage Range 2.7 5.25 V Supply Current @ 5.0V 3.0 4.2 4.9 mA Supply Current6,7 @ 2.7V 3.0 5.4 6 mA TEMPERATURE RANGE Operating Range -40 +105 °C NOTES 1 Guaranteed by measurement of initial offset and sensitivity.

2 Alignment error is specified as the angle between the true and indicated

axis of sensitivity.

3 Transverse sensitivity is the algebraic sum of the alignment and the

inherent sensitivity errors

4 The sensitivity change over temperature for thermal accelerometers is

based on variations in heat transfer that are governed by the laws of physics and it is highly consistent from device to device. Please refer to the section in this data sheet titled “Compensation for the Change of Sensitivity over Temperature” for more information. 5 The device operates over a 2.7V to 5.25V supply range. Please note that sensitivity and zero g bias level will be slightly different at 2.7V operation. For devices to be operated at 2.7V/3.0V in production, they can be trimmed at the factory specifically for this lower supply voltage operation, in which case the sensitivity and zero g bias level specifications on this page will be met. Please contact the factory for specially trimmed devices for low supply voltage operation.

6 Note that the accelerometer has a constant heater power control circuit

thereby displaying higher supply current at lower operating voltage.

MEMSIC MXD2002A/B Rev.E Page 3 of 8 5/15/2004 ABSOLUTE MAXIMUM RATINGS* Storage Temperature ……….…………-65 °C to +150°C *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. Package Characteristics Package θJA θJC Device Weight LCC-8 110°C/W 22°C/W < 1 gram Top V iew ME M SIC X +g Y +g Note: The MEMSIC logo’s arrow indicates the +X sensing direction of the device. The +Y sensing direction is rotated 90° away from the +X direction. Small circle indicates pin one(1). Pin Description: LCC-8 Package Pin Name Description

1 TOUT Temperature (Analog Voltage)

2 DOUTY Y-Axis Acceleration Digital Signal

3 Gnd Ground

4 VDA Analog Supply Voltage

5 DOUTX X-Axis Acceleration Digital Signal

6 Vref 2.5V Reference

7 Sck Optional External Clock

8 VDD Digital Supply Voltage

Model Package Style Digital Output D2002AL LCC-8 SMD* 100 Hz D2002BL LCC-8 SMD* 400 Hz *LCC parts are shipped in tape and reel packaging. Caution ESD (electrostatic discharge) sensitive device. THEORY OF OPERATION The MEMSIC device is a complete dual-axis acceleration measurement system fabricated on a monolithic CMOS IC process. The device operation is based on heat transfer by natural convection and operates like other accelerometers having a proof mass. The stationary element, or ‘proof mass’, in the MEMSIC sensor is a gas. A single heat source, centered in the silicon chip is suspended across a cavity. Equally spaced aluminum/polysilicon thermopiles (groups of thermocouples) are located equidistantly on all four sides of the heat source (dual axis). Under zero acceleration, a temperature gradient is symmetrical about the heat source, so that the temperature is the same at all four thermopiles, causing them to output the same voltage. Acceleration in any direction will disturb the temperature profile, due to free convection heat transfer, causing it to be asymmetrical. The temperature, and hence voltage output of the four thermopiles will then be different. The differential voltage at the thermopile outputs is directly proportional to the acceleration. There are two identical acceleration signal paths on the accelerometer, one to measure acceleration in the x-axis and one to measure acceleration in the y-axis. Please visit the MEMSIC website at www.memsic.com for a picture/graphic description of the free convection heat transfer principle. PIN DESCRIPTIONS VDD – This is the supply input for the digital circuits and the sensor heater in the accelerometer. The DC voltage should be between 2.70 and 5.25 volts. Refer to the section on PCB layout and fabrication suggestions for guidance on external parts and connections recommended. VDA – This is the power supply input for the analog amplifiers in the accelerometer. Refer to the section on PCB layout and fabrication suggestions for guidance on external parts and connections recommended. Gnd – This is the ground pin for the accelerometer. DOUTX – This pin is the digital output of the x-axis acceleration sensor. It is factory programmable to 100 Hz or 400 Hz. The user should ensure the load impedance is sufficiently high as to not source/sink >100µA typical. While the sensitivity of this axis has been programmed at the factory to be the same as the sensitivity for the y-axis, the accelerometer can be programmed for non-equal sensitivities on the x- and y-axes. Contact the factory for additional information. DOUTY – This pin is the digital output of the y-axis acceleration sensor. It is factory programmable to 100 Hz

MEMSIC MXD2002A/B Rev.E Page 5 of 8 5/15/2004 X-Axis Y-Axis X-Axis Orientation To Earth’s Surface (deg.) X Output (g) Change per deg. of tilt (mg) Y Output (g) Change per deg. of tilt (mg) 90 1.000 0.15 0.000 17.45 85 0.996 1.37 0.087 17.37 80 0.985 2.88 0.174 17.16 70 0.940 5.86 0.342 16.35 60 0.866 8.59 0.500 15.04 45 0.707 12.23 0.707 12.23 30 0.500 15.04 0.866 8.59 20 0.342 16.35 0.940 5.86 10 0.174 17.16 0.985 2.88 5 0.087 17.37 0.996 1.37 0 0.000 17.45 1.000 0.15 Table 1: Changes in Tilt for X- and Y-Axes Minimum Resolution: Accelerometers can be used in a wide variety of low g applications such as tilt and orientation. The device noise floor will vary with the measurement bandwidth. With the reduction of the bandwidth the noise floor drops. This will improve the signal to noise ratio of the measurement and resolution. The output noise scales directly with the square root of the measurement bandwidth. The maximum amplitude of the noise, its peak- to- peak value, approximately defines the worst case resolution of the measurement. The peak-to- peak noise is approximately equal to 6.6 times as the rms value (with an average uncertainty of .1%). The maximum noise for 1.0Hz bandwidth will be 1 mg/ Hz . If the bandwidth is increased to 10 Hz for example: 3.162 mg is the maximum rms noise and 20.87mg is the maximum peak -to-peak noise. DIGITAL INTERFACE The MXD2002A/B is easily interfaced with low cost microcontrollers. For the digital output accelerometer, one digital input port is required to read one accelerometer output. For the analog output accelerometer, many low cost microcontrollers are available today that feature integrated a/d (analog to digital converters) with resolutions ranging from 8 to 12 bits. In many applications the microcontroller provides an effective approach for the temperature compensation of the sensitivity and the zero g offset. Specific code set, reference designs, and applications notes are available from the factory. The following parameters must be considered in a digital interface: Resolution: smallest detectable change in input acceleration Bandwidth: detectable accelerations in a given period of time Acquisition Time: the duration of the measurement of the acceleration signal DUTY CYCLE DEFINITION The MXD2002A/B has two PWM duty cycle outputs (x,y). The acceleration is proportional to the ratio T1/T2. The zero g output is set to 50% duty cycle and the sensitivity scale factor is set to 2% duty cycle change per g. These nominal values are affected by the initial tolerance of the device including zero g offset error and sensitivity error. This device is offered from the factory programmed to either a 10ms period (100 Hz) or a 2.5ms period (400Hz). T1 Length of the “on” portion of the cycle. T2 (Period) Length of the total cycle. Duty Cycle Ratio of the “0n” time (T1) of the cycle to the total cycle (T2). Defined as T1/T2. Pulse width Time period of the “on” pulse. Defined as T1. 0g = 50% Duty Cycle T2= 2.5ms or 10ms (factory programmable) Figure 4: Typical output Duty C ycle CHOOSING T2 AND COUNTER FREQUENCY DESIGN TRADE-OFFS The noise level is one determinant of accelerometer resolution. The second relates to the measurement resolution of the counter when decoding the duty cycle output. The actual resolution of the acceleration signal is limited by the time resolution of the counting devices used to decode the duty cycle. The faster the counter clock, the higher the resolution of the duty cycle and the shorter the T2 period can be for a given resolution. Table 2 shows some of the trade-offs. It is important to note that this is the resolution due to the microprocessors’ counter. It is probable that the accelerometer’s noise floor may set the lower limit on the resolution. T2 (ms) MEMSIC Sample Rate Counter- Clock Rate (MHz) Counts Per T2 Cycle Counts per g Reso- lution (mg) 2.5 400 2.0 5000 100 10 2.5 400 1.0 2500 50 20 2.5 400 0.5 1250 25 40 10.0 100 2.0 20000 400 2.5 10.0 100 1.0 10000 200 5.0 10.0 100 0.5 5000 100 10 Table 2: Trade-Offs Between Microcontroller Counter Rate and T2 Period.

MEMSIC MXD2002A/B Rev.E Page 8 of 8 5/15/2004 Package Drawing Fig 10: Hermetically Sealed Package Outline