Freescale Semiconductor Technical Data MMA7261Q Rev 2.0, 3/2006 ±2.5g - 10g Three Axis Low-g Micromachined Accelerometer MMA7261Q The MMA7261Q low cost capacitive micromachined accelerometer features signal conditioning, a 1-pole low pass filter, temperature compensation and g-Select which allows for the selection among 4 sensitivities. Zero-g offset full scale span and filter cut-off are factory set and require no external devices. Includes a Sleep Mode that makes it ideal for handheld battery powered electronics. MMA7261Q: XYZ AXIS ACCELEROMETER ±2.5g/3.3g/6.7g/10g Features Selectable Sensitivity (2.5g/3.3g/6.7g/10g) Low Current Consumption: 500 µA Sleep Mode: 3 µA Low Voltage Operation: 2.2 V – 3.6 V 6mm x 6mm x 1.45mm QFN Fast Turn On Time High Sensitivity (2.5 g) Integral Signal Conditioning with Low Pass Filter Robust Design, High Shocks Survivability Environmentally Preferred Package Low Cost Bottom View 16 LEAD QFN 98ASA10651D Typical Applications HDD MP3 Player: Freefall Detection Laptop PC: Freefall Detection, Anti-Theft Cell Phone: Image Stability, Text Scroll, Motion Dialing, E-Compass Pedometer: Motion Sensing PDA: Text Scroll Navigation and Dead Reckoning: E-Compass Tilt Compensation Gaming: Tilt and Motion Sensing, Event Recorder Robotics: Motion Sensing YOUT ZOUT ORDERING INFORMATION XOUT Top View N/C 16 15 14 13 12 Sleep Mode g-Select2 2 11 N/C QFN-16, Tube VDD 3 10 N/C QFN-16,Tape & Reel VSS 4 9 N/C Package Drawing Package MMA7261Q – 20 to +85°C 98ASA10651D MMA7261QR2 – 20 to +85°C 98ASA10651D 5 6 7 8 N/C 1 Temperature Range N/C g-Select1 Device Name N/C • • • • • • • • N/C • • • • • • • • • • • Figure 1. Pin Connections © Freescale Semiconductor, Inc., 2006. All rights reserved. VDD g-Select1 g-Select2 G-Cell Sensor Sleep Mode Oscillator Clock Generator X-Temp Comp XOUT C to V Converter Gain + Filter Y-Temp Comp YOUT Z-Temp Comp ZOUT Control Logic EEPROM Trim Circuits VSS Figure 2. Simplified Accelerometer Functional Block Diagram Table 1. Maximum Ratings (Maximum ratings are the limits to which the device can be exposed without causing permanent damage.) Rating Symbol Value Unit Maximum Acceleration (all axis) gmax ±2000 g Supply Voltage VDD –0.3 to +3.6 V Drop Test(1) Ddrop 1.8 m Tstg –40 to +125 °C Storage Temperature Range 1. Dropped onto concrete surface from any axis. ELECTRO STATIC DISCHARGE (ESD) WARNING: This device is sensitive to electrostatic discharge. Although the Freescale accelerometer contains internal 2000 V 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. MMA7261Q 2 Analog Integrated Circuit Device Data Freescale Semiconductor Table 2. Operating Characteristics Unless otherwise noted: –20°C < TA < 85°C, 2.2 V < VDD < 3.6 V, Acceleration = 0g, Loaded output(1) Characteristic Symbol Min Typ Max Unit Supply Voltage(3) VDD 2.2 3.3 3.6 V Supply Current IDD — 500 800 µA Operating Range(2) Supply Current at Sleep Mode(4) IDD — 3 10 µA TA –20 — +85 °C g-Select1 & 2: 00 gFS — ±2.5 — g g-Select1 & 2: 10 gFS — ±3.3 — g g-Select1 & 2: 01 gFS — ±6.7 — g g-Select1 & 2: 11 gFS — ±10.0 — g Operating Temperature Range Acceleration Range, X-Axis, Y-Axis, Z-Axis Output Signal Zero g (TA = 25°C, VDD = 3.3 V)(5) VOFF 1.485 1.65 1.815 V VOFF, TA — ±2 — mg/°C 2.5g S2.5g 444 480 516 mV/g 3.3g S3.3g 333 360 387 mV/g 6.7g S6.7g 167 180 193 mV/g 10g S10g 111 120 129 mV/g S,TA — ±0.03 — %/°C XY f-3dB — 350 — Hz Z f-3dB — 150 — Hz nRMS — 4.7 — mVrms nPSD — 350 — µg/ Hz tRESPONSE — 1.0 2.0 ms tENABLE — 0.5 2.0 ms XY fGCELL — 6.0 — kHz Z fGCELL — 3.4 — kHz fCLK — 11 — kHz VFSO VSS+0.25 — VDD–0.25 V NLOUT –1.0 — +1.0 %FSO VXY, XZ, YZ — — 5.0 % Zero g Sensitivity (TA = 25°C, VDD = 3.3 V) Sensitivity Bandwidth Response Noise RMS (0.1 Hz – 1 kHz)(4) Power Spectral Density RMS (0.1 Hz – 1 kHz)(4) Control Timing Power-Up Response Time(6) Enable Response Time(7) Sensing Element Resonant Frequency Internal Sampling Frequency Output Stage Performance Full-Scale Output Range (IOUT = 30 µA) Nonlinearity, XOUT, YOUT, ZOUT Cross-Axis Sensitivity(8) 1. For a loaded output, the measurements are observed after an RC filter consisting of a 1.0 kΩ resistor and a 0.1 µF capacitor on VDD-GND. 2. These limits define the range of operation for which the part will meet specification. 3. Within the supply range of 2.2 and 3.6 V, 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. This value is measured with g-Select in 2.5g mode. 5. 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. For negative acceleration, the output will decrease below VDD/2. 6. The response time between 10% of full scale Vdd input voltage and 90% of the final operating output voltage. 7. The response time between 10% of full scale Sleep Mode input voltage and 90% of the final operating output voltage. 8. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity. MMA7261Q Analog Integrated Circuit Device Data Freescale Semiconductor 3 PRINCIPLE OF OPERATION The Freescale accelerometer is a surface-micromachined integrated-circuit accelerometer. The device consists of two surface micromachined capacitive sensing cells (g-cell) and a signal conditioning ASIC contained in a single integrated circuit package. The sensing elements are sealed hermetically at the wafer level using a bulk micromachined cap wafer. The g-cell is a mechanical structure formed from semiconductor materials (postillion) using semiconductor processes (masking and etching). It can be modeled as a set of beams attached to a movable central mass that move 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 (Figure 3). As the center beam moves with acceleration, the distance between the beams changes and each capacitor's value will change, (C = Aε/D). Where A is the area of the beam, ε is the dielectric constant, and D is the distance between the beams. The 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. Acceleration SPECIAL FEATURES g-Select The g-Select feature allows for the selection among 4 sensitivities present in the device. Depending on the logic input placed on pins 1 and 2, the device internal gain will be changed allowing it to function with a 2.5g, 3.3g, 6.7g, or 10g sensitivity (Table 3). This feature is ideal when a product has applications requiring different sensitivities for optimum performance. The sensitivity can be changed at anytime during the operation of the product. The g-Select1 and gSelect2 pins can be left unconnected for applications requiring only a 2.5g sensitivity as the device has an internal pull-down to keep it at that sensitivity (480mV/g). Table 3. g-Select pin Descriptions g-Select2 g-Select1 g-Range Sensitivity 0 0 2.5g 480mV/g 0 1 3.3g 360mV/g 1 0 6.7g 180mV/g 1 1 10g 120mV/g Sleep Mode The 3 axis accelerometer provides a Sleep Mode that is ideal for battery operated products. When Sleep Mode is active, the device outputs are turned off, providing significant reduction of operating current. A low input signal on pin 12 (Sleep Mode) will place the device in this mode and reduce the current to 3uA typ. For lower power consumption, it is recommended to set g-Select1 and g-Select2 to 2.5g mode. By placing a high input signal on pin 12, the device will resume to normal mode of operation. Filtering The 3 axis accelerometer contains onboard single-pole switched capacitor filters. 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. Figure 3. Simplified Transducer Physical Model Ratiometricity Ratiometricity simply means the output offset voltage and sensitivity will scale linearly with applied supply voltage. That is, as supply voltage is increased, the sensitivity and offset increase linearly; as supply voltage decreases, offset and sensitivity decrease linearly. This is a key feature when interfacing to a microcontroller or an A/D converter because it provides system level cancellation of supply induced errors in the analog to digital conversion process. MMA7261Q 4 Analog Integrated Circuit Device Data Freescale Semiconductor BASIC CONNECTIONS PCB Layout Pin Descriptions XOUT YOUT ZOUT 16 15 14 13 g-Select1 1 POWER SUPPLY VDD 12 Sleep Mode C C VRH VDD P0 VSS 11 NC VDD 3 10 NC g-Select1 P1 g-Select2 P2 VSS 4 5 6 7 8 NC NC NC NC 9 NC Figure 4. Pinout Description Table 4. Pin Descriptions Accelerometer g-Select2 2 VSS Sleep Mode XOUT R YOUT R ZOUT R C C C A/DIN C Microcontroller NC Top View A/DIN A/DIN Pin No. Pin Name 1 g-Select1 Logic input pin to select g level. 2 g-Select2 Logic input pin to select g level. 3 VDD Power Supply Input 4 VSS Power Supply Ground 5-7 N/C No internal connection. Leave unconnected. 8 - 11 N/C Unused for factory trim. Leave unconnected. 2. Physical coupling distance of the accelerometer to the microcontroller should be minimal. 12 Sleep Mode Logic input pin to enable product or Sleep Mode. 3. Flag underneath package is connected to ground. 13 ZOUT Z direction output voltage. 14 YOUT Y direction output voltage. 15 XOUT X direction output voltage. 16 N/C Logic Inputs Description No internal connection. Leave unconnected. NOTES: 1. Use 0.1 µF capacitor on VDD to decouple the power source. Do not exceed capacitor values of 2.2 or 3.3 µF on VDD-GND. 4. 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. 5. Use an RC filter with 1.0 kΩ and 0.1 µF on the outputs of the accelerometer to minimize clock noise (from the switched capacitor filter circuit). 6. PCB layout of power and ground should not couple power supply noise. 1 g-Select1 ZOUT 13 1 kΩ 0.1 µF 2 g-Select2 VDD Figure 6. Recommended PCB Layout for Interfacing Accelerometer to Microcontroller MMA7261Q 3 VDD YOUT 14 0.1 µF 1 kΩ 7. Accelerometer and microcontroller should not be a high current path. 8. 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 (11 kHz for the sampling frequency). This will prevent aliasing errors. 0.1 µF 4 12 VSS XOUT 15 Sleep Mode Logic Input 1 kΩ 0.1 µF Figure 5. Accelerometer with Recommended Connection Diagram MMA7261Q Analog Integrated Circuit Device Data Freescale Semiconductor 5 DYNAMIC ACCELERATION Top View +Y 14 13 12 2 11 3 10 4 9 5 6 7 -X -Z Bottom +X 15 1 Top 16 Side View +Z 8 -Y : Arrow indicates direction of mass movement. 16-Pin QFN Package STATIC ACCELERATION Direction of Earth’s gravity field.* Top View Side View XOUT@ 0g = 1.65 V YOUT @ -1g = 1.17 V ZOUT @ 0g = 1.65 V XOUT @ +1g = 2.13 V YOUT @ 0g = 1.65 V ZOUT @ 0g = 1.65 V XOUT @ 0g = 1.65 V YOUT @ 0g = 1.65 V ZOUT @ +1g = 2.13 V XOUT @ -1g = 1.17 V YOUT @ 0g = 1.65 V ZOUT @ 0g = 1.65 V XOUT @ 0g = 1.65 V YOUT @ 0g = 1.65 V ZOUT @ -1g = 1.17 V XOUT @ 0g = 1.65 V YOUT @ +1g = 2.13 V ZOUT @ 0g = 1.65 V * When positioned as shown, the Earth’s gravity will result in a positive 1g output. MMA7261Q 6 Analog Integrated Circuit Device Data Freescale Semiconductor MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS Surface mount board layout is a critical portion of the total design. The footprint for the surface mount packages must be the correct size to ensure proper solder connection interface between the board and the package. With the correct footprint, the packages will self-align when subjected to a solder reflow process. It is always recommended to design boards with a solder mask layer to avoid bridging and shorting between solder pads. 6.0 0.55 4.25 9 6.0 8 13 12 5 16 0.50 1.00 1 4 Solder areas Pin 1 ID (non metallic) PACKAGE DIMENSIONS For the most current package revision, visit www.freescale.com and perform a keyword search using the “98A” listed below. 6 PIN 1 INDEX AREA DETAIL G A M 0.1 C 2X 0.10 C 0.08 C 1.45±0.1 5 6 (0.203) (0.102) C SEATING PLANE DETAIL G 2X M 0.10 C B (0.5) (1) VIEW ROTATED 90˚ CLOCKWISE 4 0.1 C A B 16X 4.24 4.04 EXPOSED DIE ATTACH PAD 13 (45˚) 0.1 DETAIL M PIN 1 INDEX 16 DETAIL M 12 4.24 4.04 0.5 1 0.1 C A B 9 4 12X 8 16X 1 5 0.63 0.43 16X VIEW M-M 0.60 0.40 0.1 M C A B 0.05 M C 3 NOTES: 1. ALL DIMENSIONS ARE IN MILLIMETERS. 2. INTERPRET DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994. 3. THIS DIMENSION APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25MM AND 0.30MM FROM TERMINAL TIP. 4. THIS DIMENSION REPRESENTS TERMINAL FULL BACK FROM PACKAGE EDGE UP TO 0.1MM IS ACCEPTABLE. 5. COPLANARITY APPLIES TO THE EXPOSED HEAT SLUG AS WELL AS THE TERMINAL. 6. RADIUS ON TERMINAL IS OPTIONAL. 7. MINIMUM METAL GAP 0.2MM. 98ASA10651D ISSUE O 16-LEAD QFN MMA7261Q Analog Integrated Circuit 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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