Freescale Semiconductor Technical Data MMA1260D Rev. 1, 10/2004 Low G Micromachined Accelerometer MMA1260D The MMA series of silicon capacitive, micromachined accelerometers features signal conditioning, a 2--pole low pass filter and temperature compensation. Zero--g 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. MMA1260D: Z AXIS SENSITIVITY MICROMACHINED ACCELEROMETER ±1.5g Features • Integral Signal Conditioning • Linear Output • 2nd Order Bessel Filter • Calibrated Self--test • EPROM Parity Check Status 16 • Transducer Hermetically Sealed at Wafer Level for Superior Reliability • Robust Design, High Shock Survivability 9 1 Typical Applications 8 • Vibration Monitoring and Recording 16 LEAD SOIC CASE 475--01 • Appliance Control • Mechanical Bearing Monitoring • Computer Hard Drive Protection • Computer Mouse and Joysticks Pin Assignment • Virtual Reality Input Devices • Sports Diagnostic Devices and Systems VSS VSS VSS VOUT ORDERING INFORMATION Device Temperature Range MMA1260D --40 to +105°C Case No. Package Case 475--01 SOIC--16 STATUS VDD VSS ST 16 15 14 13 12 11 10 1 2 3 4 5 6 7 8 9 N/C N/C N/C N/C N/C N/C N/C N/C SIMPLIFIED ACCELEROMETER FUNCTIONAL BLOCK DIAGRAM VDD G--CELL SENSOR ST SELF--TEST INTEGRATOR GAIN CONTROL LOGIC & EPROM TRIM CIRCUITS FILTER OSCILLATOR TEMP COMP & GAIN CLOCK GEN. VOUT VSS STATUS Figure 1. Simplified Accelerometer Functional Block Diagram REV 1 © Freescale Semiconductor, Inc., 2004. All rights reserved. Sensor Device Data Freescale Semiconductor MMA1260D 1 MAXIMUM RATINGS (Maximum ratings are the limits to which the device can be exposed without causing permanent damage.) Symbol Value Unit Powered Acceleration (all axes) gpd 1500 g Unpowered Acceleration (all axes) gupd 2000 g Supply Voltage VDD --0.3 to +7.0 V Hdrop 1.2 m Tstg --40 to +125 °C Rating Drop Test(1) Storage Temperature Range NOTES: 1. Dropped onto concrete surface from any axis. ELECTRO STATIC DISCHARGE (ESD) WARNING: This device is sensitive to electrostatic discharge. Although the Freescale Semiconductor 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. MMA1260D 2 Sensor Device Data Freescale Semiconductor OPERATING CHARACTERISTICS (Unless otherwise noted: --40°C ≤ TA ≤ +105°C, 4.75 ≤ VDD ≤ 5.25, Acceleration = 0g, Loaded output(1)) Symbol Min Typ Max Unit VDD IDD TA gFS 4.75 1.1 −40 — 5.00 2.2 — 1.5 5.25 3.2 +105 — V mA °C g VOFF VOFF S S f --3dB NLOUT 2.25 2.2 1140 1110 40 −1.0 2.5 2.5 1200 1200 50 — 2.75 2.8 1260 1290 60 +1.0 V V mV/g mV/g Hz % FSO Noise RMS (0.1 Hz -- 1.0 kHz) Spectral Density (RMS, 0.1 Hz -- 1.0 kHz)(6) nRMS nSD — — 5.0 500 9.0 — mVrms µg/√Hz Self--Test Output Response (VDD = 5.0 V) Input Low Input High Input Loading(7) Response Time(8) ∆VST VIL VIH IIN tST 0.3 VSS 0.7 VDD −50 — 0.6 — — −125 10 0.9 0.3 VDD VDD −300 25 V V V µA ms Status(12)(13) Output Low (Iload = 100 µA) Output High (Iload = --100 µA) VOL VOH — VDD −0.8 — — 0.4 — V V Output Stage Performance Electrical Saturation Recovery Time(9) Full Scale Output Range (IOUT = --200 µA) Capacitive Load Drive(10) Output Impedance tDELAY VFSO CL ZO — VSS+0.25 — — — — — 50 2.0 VDD−0.25 100 — ms V pF Ω Mechanical Characteristics Transverse Sensitivity(11) VXZ,YZ — — 5.0 % FSO Characteristic Range(2) Operating Supply Voltage(3) Supply Current Operating Temperature Range Acceleration Range Output Signal Zero g (TA = 25°C, VDD = 5.0 V)(4) Zero g (VDD = 5.0 V) Sensitivity (TA = 25°C, VDD = 5.0 V)(5) Sensitivity (VDD = 5.0 V) Bandwidth Response Nonlinearity NOTES: 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. Time for amplifiers to recover after an acceleration signal causing them to saturate. 10. Preserves phase margin (60°) to guarantee output amplifier stability. 11. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity. 12. 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. 13. 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. MMA1260D Sensor Device Data Freescale Semiconductor 3 PRINCIPLE OF OPERATION SPECIAL FEATURES The Freescale Semiconductor 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 two stationary plates with a moveable plate in--between. The center plate can be deflected from its rest position by subjecting the system to an acceleration (Figure 2). When the center plate deflects, the distance from it to one fixed plate will increase by the same amount that the distance to the other plate decreases. The change in distance is a measure of acceleration. The g--cell plates form two back--to--back capacitors (Figure 3). As the center plate moves with acceleration, the distance between the plates changes and each capacitor’s value will change, (C = Aε/D). Where A is the area of the plate, ε is the dielectric constant, and D is the distance between the plates. 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. Filtering The Freescale Semiconductor accelerometers contain an onboard 2--pole switched capacitor filter. A Bessel implementation is used because it provides a maximally flat delay response (linear phase) thus preserving pulse shape integrity. 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. Acceleration Figure 2. Transducer Physical Model 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 Semiconductor 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. Figure 3. Equivalent Circuit Model MMA1260D 4 Sensor Device Data Freescale Semiconductor BASIC CONNECTIONS 9 ACCELEROMETER STATUS VDD VSS ST STATUS N/C N/C N/C N/C N/C N/C N/C N/C 16 15 14 13 12 11 10 1 2 3 4 5 6 7 8 P1 ST P0 VOUT R VSS 1 kΩ VDD A/D IN C 0.1 µF C 0.1 µF VRH C MICROCONTROLLER VSS VSS VSS VOUT PCB Layout VSS C 0.1 µF VDD 0.1 µF Figure 4. Pinout Description POWER SUPPLY Pin No. Pin Name Description 1 thru 3 VSS Redundant connections to the internal VSS and may be left unconnected. 4 VOUT 5 STATUS 6 VDD The power supply input. 7 VSS The power supply ground. NOTES: 8 ST Logic input pin used to initiate self-test. 9 thru 13 Trim pins Used for factory trim. Leave unconnected. • Use a 0.1 µF capacitor on VDD to decouple the power source. 14 thru 16 — No internal connection. Leave unconnected. VDD Output voltage of the accelerometer. Logic output pin used to indicate fault. MMA1260D LOGIC INPUT Figure 6. Recommended PCB Layout for Interfacing Accelerometer to Microcontroller 5 8 ST 6 VDD C1 0.1 µF 7 VSS VOUT 4 • Physical coupling distance of the accelerometer to the microcontroller should be minimal. • Place a ground plane beneath the accelerometer to reduce noise, the ground plane should be attached to all internal VSS terminals shown in Figure 4. STATUS R1 1 kΩ OUTPUT SIGNAL C2 0.1 µF Figure 5. SOIC Accelerometer with Recommended Connection Diagram • Use an RC filter of 1 kΩ and 0.1 µF on the output of the accelerometer to minimize clock noise (from the switched capacitor filter circuit). • PCB layout of power and ground should not couple power supply noise. • Accelerometer and microcontroller should not be a high current path. • 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. MMA1260D Sensor Device Data Freescale Semiconductor 5 ACCELERATION SENSING DIRECTIONS DYNAMIC ACCELERATION VSS VSS VSS VOUT +g STATUS VDD VSS 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 16--Pin SOIC Package N/C pins are recommended to be left FLOATING --g STATIC ACCELERATION Direction of Earth’s gravity field.* +1g VOUT = 3.7V 0g 0g VOUT = 2.50V VOUT = 2.50V --1g VOUT = 1.3V * When positioned as shown, the Earth’s gravity will result in a positive 1g output MMA1260D 6 Sensor Device Data Freescale Semiconductor PACKAGE DIMENSIONS A A G/2 2 PLACES, 16 TIPS G 16 NOTES: 1. ALL DIMENSIONS ARE IN MILLIMETERS. 2. INTERPRET DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994. 3. DIMENSIONS ”A” AND ”B” DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.15 PER SIDE. 4. DIMENSION ”D” DOES NOT INCLUDE DAMBAR PROTRUSION. PROTRUSIONS SHALL NOT CAUSE THE LEAD WIDTH TO EXCEED 0.75 0.15 T A B 9 B P 1 B 8 16X D 0.13 M T A B R J C 0.1 T X 45 _ K F DIM A B C D F G J K M P R MILLIMETERS MIN MAX 10.15 10.45 7.40 7.60 3.30 3.55 0.35 0.49 0.76 1.14 1.27 BSC 0.25 0.32 0.10 0.25 0_ 7_ 10.16 10.67 0.25 0.75 M SEATING PLANE CASE 475--01 ISSUE B 16 LEAD SOIC MMA1260D Sensor Device Data Freescale Semiconductor 7 How to Reach Us: Home Page: www.freescale.com E--mail: [email protected] USA/Europe or Locations Not Listed: Freescale Semiconductor Technical Information Center, CH370 1300 N. Alma School Road Chandler, Arizona 85224 +1--800--521--6274 or +1--480--768--2130 [email protected] Europe, Middle East, and Africa: Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen, Germany +44 1296 380 456 (English) +46 8 52200080 (English) +49 89 92103 559 (German) +33 1 69 35 48 48 (French) [email protected] Japan: Freescale Semiconductor Japan Ltd. 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Freescalet 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. 2004. All rights reserved. MMA1260D Rev. 1 10/2004 MMA1260D 8 Sensor Device Data Freescale Semiconductor