MMA2260

Freescale Semiconductor Technical Data Document Number: MMA2260D Rev 3, 03/2006 ±1.5g X-Axis Micromachined Accelerometer The MMA series of silicon capacitive, micromachined accelerometers feature signal conditioning, a 2-pole low pass filter and temperature compensation. Zerog offset full scale span and filter cut-off are factory set and require no external devices. A full system self-test capability verifies system functionality. Features • • • • • • • • Integral Signal Conditioning High Sensitivity Linear Output 2nd Order Bessel Filter Calibrated Self-test EPROM Parity Check Status Transducer Hermetically Sealed at Wafer Level for Superior Reliability Robust Design, High Shock Survivability MMA2260 MMA2260D: X AXIS SENSITIVITY MICROMACHINED ACCELEROMETER ±1.5g Typical Applications • • • • • • • • Tilt Monitoring Inclinometers Appliance Control Mechanical Bearing Monitoring Vibration Monitoring and Recording Sports Diagnostic Devices and Systems Trailer Brake Controls Automotive Aftermarket ORDERING INFORMATION Device MMA2260D MMA2260DR2 MMA2260EG MMA2260EGR2 Temperature Range –40 to +105°C –40 to +105°C –40 to +105°C –40 to +105°C Case No. 475-01 475-01 475-01 475-01 Package SOIC-16 SOIC-16, Tape & Reel SOIC-16 SOIC-16, Tape & Reel D SUFFIX EG SUFFIX (Pb-FREE) 16-LEAD SOIC CASE 475-01 VDD G-Cell Sensor Integrator Gain Filter Temp Comp and Gain VOUT VSS VSS VSS ST Self-test Control Logic & EPROM Trim Circuits Oscillator Clock Generator VOUT VSS STATUS VDD ST STATUS 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 N/C N/C N/C N/C N/C N/C N/C N/C Figure 1. Simplified Accelerometer Functional Block Diagram Figure 2. Pin Connections © Freescale Semiconductor, Inc., 2006. All rights reserved. Table 1. Maximum Ratings(1) (Maximum ratings are the limits to which the device can be exposed without causing permanent damage.) Rating Unpowered Acceleration (all axes) Supply Voltage Drop Test(1) Storage Temperature Range 1. Dropped onto concrete surface from any axis. Symbol gupd VDD Hdrop Tstg Value 2000 -0.3 to +7.0 1.2 -40 to +125 Unit g V m °C ELECTRO STATIC DISCHARGE (ESD) WARNING: This device is sensitive to electrostatic discharge. Although the Freescale accelerometers contain internal 2kV ESD protection circuitry, extra precaution must be taken by the user to protect the chip from ESD. A charge of over 2000 volts can accumulate on the human body or associated test equipment. A charge of this magnitude can alter the performance or cause failure of the chip. When handling the accelerometer, proper ESD precautions should be followed to avoid exposing the device to discharges which may be detrimental to its performance. MMA2260D 2 Sensors Freescale Semiconductor Table 2. Operating Characteristics (Unless otherwise noted: –40°C ≤ TA ≤ +105°C, 4.75 ≤ VDD ≤ 5.25, Acceleration = 0g, Loaded output(1)) Characteristic Operating Range(2) Supply Voltage(3) Supply Current Operating Temperature Range Acceleration Range Output Signal Zero g (VDD = 5.0 V)(4) Sensitivity (TA = 25°C, VDD = 5.0 V)(5) Sensitivity (VDD = 5.0 V)(5) Bandwidth Response Nonlinearity Noise RMS (0.1 Hz – 1.0 kHz) Spectral Density (RMS, 0.1 Hz – 1.0 kHz)(6) Self-Test Output Response (VDD = 5.0 V) Input Low Input High Input Loading(7) Response Time(8) Status(9)(10) Output Low (Iload = 100 µA) Output High (Iload = –100 µA) Output Stage Performance Electrical Saturation Recovery Time(11) Full Scale Output Range (IOUT = –200 µA) Capacitive Load Drive(12) Output Impedance Mechanical Characteristics Transverse Sensitivity(13) Symbol VDD IDD TA gFS VOFF S S f –3dB NLOUT nRMS nSD ∆VST VIL VIH IIN tST VOL VOH tDELAY VFSO CL ZO VYX,ZX Min 4.75 1.1 –40 – 2.3 1140 1110 40 –1.0 – – 0.3 VSS 0.7 VDD –50 – – VDD –0.8 – VSS+0.25 – – – Typ 5.00 2.2 – 1.5 2.5 1200 1200 50 – 3.5 350 0.4 – – –125 20 – – – – – 50 – Max 5.25 3.2 +105 – 2.7 1260 1290 60 +1.0 – – 0.5 0.3 VDD VDD –300 25 0.4 – 2.0 VDD–0.25 100 – 5.0 Unit V mA °C g V mV/g mV/g Hz % FSO mVrms µg/√Hz V V V µA ms V V ms V pF Ω % FSO 1. For a loaded output the measurements are observed after an RC filter consisting of a 1 kΩ resistor and a 0.1 µF capacitor to ground. 2. These limits define the range of operation for which the part will meet specification. 3. Within the supply range of 4.75 and 5.25 volts, the device operates as a fully calibrated linear accelerometer. Beyond these supply limits the device may operate as a linear device but is not guaranteed to be in calibration. 4. The device can measure both + and – acceleration. With no input acceleration the output is at midsupply. For positive acceleration the output will increase above VDD/2 and for negative acceleration the output will decrease below VDD/2. 5. Sensitivity limits apply to 0 Hz acceleration. 6. At clock frequency ≅ 34 kHz. 7. The digital input pin has an internal pull-down current source to prevent inadvertent self test initiation due to external board level leakages. 8. Time for the output to reach 90% of its final value after a self-test is initiated. 9. The Status pin output is not valid following power-up until at least one rising edge has been applied to the self-test pin. The Status pin is high whenever the self-test input is high. 10. The Status pin output latches high if the EPROM parity changes to odd. The Status pin can be reset by a rising edge on self-test, unless a fault condition continues to exist. 11. Time for amplifiers to recover after an acceleration signal causes them to saturate. 12. Preserves phase margin (60°) to guarantee output amplifier stability. 13. A measure of the device's ability to reject an acceleration applied 90° from the true axis of sensitivity. MMA2260D Sensors Freescale Semiconductor 3 PRINCIPLE OF OPERATION The Freescale accelerometer is a surface-micromachined integrated-circuit accelerometer. The device consists of a surface micromachined capacitive sensing cell (g-cell) and a CMOS signal conditioning ASIC contained in a single integrated circuit package. The sensing element is sealed hermetically at the wafer level using a bulk micromachined “cap'' wafer. The g-cell is a mechanical structure formed from semiconductor materials (polysilicon) using semiconductor processes (masking and etching). It can be modeled as a set of beams attached to a movable central mass that moves between fixed beams. The movable beams can be deflected from their rest position by subjecting the system to an acceleration (Figure 3). As the beams attached to the central mass move, the distance from them to the fixed beams on one side will increase by the same amount that the distance to the fixed beams on the other side decreases. The change in distance is a measure of acceleration. The g-cell beams form two back-to-back capacitors (). As the central mass moves with acceleration, the distance between the beams change and each capacitor's value will change, (C = NAε/D). Where A is the area of the facing side of the beam, e is the dielectric constant, D is the distance between the beams, and N is the number of beams. The CMOS ASIC uses switched capacitor techniques to measure the g-cell capacitors and extract the acceleration data from the difference between the two capacitors. The ASIC also signal conditions and filters (switched capacitor) the signal, providing a high level output voltage that is ratiometric and proportional to acceleration. SPECIAL FEATURES Filtering Freescale accelerometers contain an onboard 2-pole switched capacitor filter. Because the filter is realized using switched capacitor techniques, there is no requirement for external passive components (resistors and capacitors) to set the cut-off frequency. Self-Test The sensor provides a self-test feature that allows the verification of the mechanical and electrical integrity of the accelerometer at any time before or after installation. A fourth “plate'' is used in the g-cell as a self-test plate. When the user applies a logic high input to the self-test pin, a calibrated potential is applied across the self-test plate and the moveable plate. The resulting electrostatic force (Fe = 1/2 AV2/d2) causes the center plate to deflect. The resultant deflection is measured by the accelerometer's control ASIC and a proportional output voltage results. This procedure assures that both the mechanical (g-cell) and electronic sections of the accelerometer are functioning. Status Freescale accelerometers include fault detection circuitry and a fault latch. The Status pin is an output from the fault latch, OR'd with self-test, and is set high whenever the following event occurs: • Parity of the EPROM bits becomes odd in number. The fault latch can be reset by a rising edge on the self-test input pin, unless one (or more) of the fault conditions continues to exist. Acceleration Figure 3. Transducer Physical Model Figure 4. Equivalent Circuit Model MMA2260D 4 Sensors Freescale Semiconductor BASIC CONNECTIONS Pinout Description PCB Layout VSS VSS VSS VOUT STATUS VDD ST . 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 N/C N/C N/C N/C N/C N/C N/C N/C STATUS Accelerometer ST VOUT VSS VDD R 1 kΩ C 0.1 µF P1 Microcontroller P0 A/D In C 0.01 µF VSS C 0.1 µF VDD VRH C 0.1 µF Table 3. Pin Description Pin No. 1 thru 3 Pin Name VSS Description Redundant connections to the internal VSS and may be left unconnected. Output voltage of the accelerometer. Logic output pin to indicate fault. The power supply ground. The power supply input. Logic input pin used to initiate self-test. Used for factory trim. Leave unconnected. No internal connection. Leave unconnected. Power Supply Figure 6. Recommended PCB Layout for Interfacing Accelerometer to Microcontroller NOTES: 1. Use a 0.1 µF capacitor on VDD to decouple the power source. 2. Physical coupling distance of the accelerometer to the microcontroller should be minimal. 3. Place a ground plane beneath the accelerometer to reduce noise, the ground plane should be attached to all of the open ended terminals shown in Figure 6. 4. Use an RC filter of 1 kΩ and 0.01 µF on the output of the accelerometer to minimize clock noise (from the switched capacitor filter circuit). 5. PCB layout of power and ground should not couple power supply noise. 6. Accelerometer and microcontroller should not be a high current path. 4 5 6 7 8 9 thru 13 14 thru 16 VOUT STATUS VDD VSS ST Trim pins — VDD Logic Input 8 MMA2260D ST VOUT 5 R1 1 kΩ STATUS Output Signal 6 VDD 4 7. A/D sampling rate and any external power supply switching frequency should be selected such that they do not interfere with the internal accelerometer sampling frequency. This will prevent aliasing errors. C1 0.1 µF 7 VSS C2 0.01 µF Figure 5. SOIC Accelerometer with Recommended Connection Diagram MMA2260D Sensors Freescale Semiconductor 5 DYNAMIC ACCELERATION 1 2 16 15 14 13 12 11 10 9 +X 3 4 5 6 7 8 -X 16-Pin SOIC Package Top View STATIC ACCELERATION Direction of Earth's gravity field.(1) -1g VOUT = 3.7V 0g VOUT = 2.50V 0g VOUT = 2.50V +1g VOUT = 1.3V 1. When positioned as shown, the Earth's gravity will result in a positive 1g output MMA2260D 6 Sensors Freescale Semiconductor PACKAGE DIMENSIONS PAGE 1 OF 2 CASE 475-01 ISSUE C 16-LEAD SOIC MMA2260D Sensors Freescale Semiconductor 7 PACKAGE DIMENSIONS PAGE 2 OF 2 CASE 475-01 ISSUE C 16-LEAD SOIC MMA2260D 8 Sensors Freescale Semiconductor How to Reach Us: Home Page: www.freescale.com E-mail: support@freescale.com USA/Europe or Locations Not Listed: Freescale Semiconductor Technical Information Center, CH370 1300 N. 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Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc., 2006. All rights reserved. MMA2260D Rev. 3 03/2006