MMA7361L_IcpdfCom_1266090

Document Number: MMA7361L Rev 0, 04/2008 Freescale Semiconductor Technical Data ±1.5g, ±6g Three Axis Low-g Micromachined Accelerometer The MMA7361L is a low power, low profile capacitive micromachined accelerometer featuring signal conditioning, a 1-pole low pass filter, temperature compensation, self test, 0g-Detect which detects linear freefall, and g-Select which allows for the selection between 2 sensitivities. Zero-g offset and sensitivity are factory set and require no external devices. The MMA7361L includes a Sleep Mode that makes it ideal for handheld battery powered electronics. Features • 3mm x 5mm x 1.0mm LGA-14 Package • Low Current Consumption: 400 μA • Sleep Mode: 3 μA • Low Voltage Operation: 2.2 V – 3.6 V • High Sensitivity (800 mV/g @ 1.5g) • Selectable Sensitivity (±1.5g, ±6g) • Fast Turn On Time (0.5 ms Enable Response Time) • Self Test for Freefall Detect Diagnosis • 0g-Detect for Freefall Protection • Signal Conditioning with Low Pass Filter • Robust Design, High Shocks Survivability • RoHS Compliant • Environmentally Preferred Product • Low Cost Typical Applications • 3D Gaming: Tilt and Motion Sensing, Event Recorder • 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 • Robotics: Motion Sensing ORDERING INFORMATION Part Number Temperature Range Package Drawing Package Shipping MMA7361LT –40 to +85°C 1977-01 LGA-14 Tray MMA7361LR1 –40 to +85°C 1977-01 LGA-14 7” Tape & Reel MMA7361LR2 –40 to +85°C 1977-01 LGA-14 13” Tape & Reel MMA7361L MMA7361L: XYZ AXIS ACCELEROMETER ±1.5g, ±6g 14 LEAD LGA CASE 1977-01 Bottom View Figure 1. Pin Connections Top View 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 N/C XOUT ZOUT YOUT VSS VDD Sleep N/C 0g-Detect g-Select Self Test N/C N/C N/C © Freescale Semiconductor, Inc., 2008. All rights reserved. MMA7361L Figure 2. Simplified Accelerometer Functional Block Diagram 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. 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 ±5000 g Supply Voltage VDD –0.3 to +3.6 V Drop Test(1) 1. Dropped onto concrete surface from any axis. Ddrop 1.8 m Storage Temperature Range Tstg –40 to +125 °C Sleep Self Test C to V CONVERTER XOUT YOUT ZOUT OSCILLATOR CLOCKGEN g-Select X-TEMP COMP G-CELL SENSOR GAIN + FILTER CONTROL LOGIC NVM TRIM CIRCUITS Y-TEMP COMP Z-TEMP COMP VDD VSS 0g-Detect SELFTEST Sleep Self Test C to V CONVERTER XOUT YOUT ZOUT OSCILLATOR CLOCKGEN g-Select X-TEMP COMP G-CELL SENSOR GAIN + FILTER CONTROL LOGIC NVM TRIM CIRCUITS Y-TEMP COMP Z-TEMP COMP VDD VSS 0g-Detect SELFTEST Sensors 2 Freescale Semiconductor Table 2. Operating Characteristics MMA7361L Unless otherwise noted: -40°C < TA < 85°C, 2.2 V < VDD < 3.6 V, Acceleration = 0g, Loaded output(1) Characteristic Symbol Min Typ Max Unit Operating Range(2) Supply Voltage(3) Supply Current(4) Supply Current at Sleep Mode(4) Operating Temperature Range Acceleration Range, X-Axis, Y-Axis, Z-Axis g-Select: 0 g-Select: 1 VDD IDD IDD TA gFS gFS 2.2 — — -40 — — 3.3 400 3 — ±1.5 ±6.0 3.6 600 10 +85 — — V μA μA °C g g Output Signal Zero-g (TA = 25°C, VDD = 3.3 V)(5), (6) Zero-g(4) Sensitivity (TA = 25°C, VDD = 3.3 V) 1.5g 6g Sensitivity(4) Bandwidth Response XY Z Output Impedance 0g-Detect VOFF VOFF, TA S1.5g S6g S,TA f-3dBXY f-3dBZ ZO 0gdetect 1.485 -2.0 740 190.6 -0.0075 — — — -0.4 1.65 ±0.5 800 206 ±0.002 400 300 32 0 1.815 +2.0 860 221.5 +0.0075 — — — +0.4 V mg/°C mV/g mV/g %/°C Hz Hz kΩ g Self Test Output Response XOUT, YOUT ZOUT Input Low Input High ΔgSTXY ΔgSTZ VIL VIH +0.05 +0.8 VSS 0.7 VDD -0.1 +1.0 — — — +1.2 0.3 VDD VDD g g V V Noise Power Spectral Density RMS (0.1 Hz – 1 kHz)(4) nPSD — 350 — μg/ Control Timing Power-Up Response Time(7) Enable Response Time(8) Self Test Response Time(9) Sensing Element Resonant Frequency XY Z Internal Sampling Frequency tRESPONSE tENABLE tST fGCELLXY fGCELLZ fCLK — — — — — — 1.0 0.5 2.0 6.0 3.4 11 2.0 2.0 5.0 — — — ms ms ms kHz kHz kHz Output Stage Performance Full-Scale Output Range (IOUT = 3 µA) VFSO VSS+0.1 — VDD–0.1 V Nonlinearity, XOUT, YOUT, ZOUT NLOUT -1.0 — +1.0 %FSO Cross-Axis Sensitivity(10) VXY, XZ, YZ -5.0 — +5.0 % 1. For a loaded output, the measurements are observed after an RC filter consisting of an internal 32kΩ resistor and an external 3.3nF capacitor (recommended as a minimum to filter clock noise) on the analog output for each axis and a 0.1μF capacitor on VDD - GND. The output sensor bandwidth is determined by the Capacitor added on the output. f = 1/2π * (32 x 103) * C. C = 3.3 nF corresponds to BW = 1507HZ, which is the minimum to filter out internal clock noise. 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 1.5g 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. For optimal 0g offset performance, adhere to AN3484 and AN3447 7. The response time between 10% of full scale VDD input voltage and 90% of the final operating output voltage. 8. The response time between 10% of full scale Sleep Mode input voltage and 90% of the final operating output voltage. 9. The response time between 10% of the full scale self test input voltage and 90% of the self test output voltage. 10. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity. Hz Sensors Freescale Semiconductor 3 PRINCIPLE OF OPERATION MMA7361L The Freescale accelerometer is a surface-micromachined integrated-circuit accelerometer. The device consists of a surface micromachined capacitive sensing cell (g-cell) and a signal conditioning ASIC contained in a single 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 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. Figure 3. Simplified Transducer Physical Model SPECIAL FEATURES 0g-Detect The sensor offers a 0g-Detect feature that provides a logic high signal when all three axes are at 0g. This feature enables the application of Linear Freefall protection if the signal is connected to an interrupt pin or a poled I/O pin on a microcontroller. 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. This feature is critical in applications such as hard disk drive protection where system integrity must be ensured over the life of the product. Customers can use self test to verify the solderability to confirm that the part was mounted to the PCB correctly. To use this feature to verify the 0g-Detect function, the accelerometer should be held upside down so that the z-axis experiences -1g. When the self test function is initiated, an electrostatic force is applied to each axis to cause it to deflect. The x- and y-axis are deflected slightly while the z-axis is trimmed to deflect 1g. This procedure assures that both the mechanical (g-cell) and electronic sections of the accelerometer are functioning. g-Select The g-Select feature allows for the selection between two sensitivities. Depending on the logic input placed on pin 10, the device internal gain will be changed allowing it to function with a 1.5g or 6g sensitivity (Table 3). This feature is ideal when a product has applications requiring two different sensitivities for optimum performance. The sensitivity can be changed at anytime during the operation of the product. The g-Select pin can be left unconnected for applications requiring only a 1.5g sensitivity as the device has an internal pull-down to keep it at that sensitivity (800mV/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 7 (Sleep Mode) will place the device in this mode and reduce the current to 3 μA typ. For lower power consumption, it is recommended to set g-Select to 1.5g mode. By placing a high input signal on pin 7, the device will resume to normal mode of operation. Filtering The 3 axis accelerometer contains an onboard single-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. 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. Acceleration Table 3. g-Select Pin Description g-Select g-Range Sensitivity 0 1.5g 800 mV/g 1 6g 206 mV/g Sensors 4 Freescale Semiconductor BASIC CONNECTIONS MMA7361L Pin Descriptions Figure 4. Pinout Description Figure 5. Accelerometer with Recommended Connection Diagram PCB Layout Figure 6. Recommended PCB Layout for Interfacing Accelerometer to Microcontroller NOTES: 1. Use 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 a 3.3nF capacitor on the outputs 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. 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 (11 kHz for the sampling frequency). This will prevent aliasing errors. 8. 10MΩ or higher is recommended on XOUT, YOUT and ZOUT to prevent loss due to the voltage divider relationship between the internal 32 kΩ resistor and the measurement input impedance. Table 4. Pin Descriptions Pin No. Pin Name Description 1 N/C No internal connection Leave unconnected 2 XOUT X direction output voltage 3 YOUT Y direction output voltage 4 ZOUT Z direction output voltage 5 VSS Power Supply Ground 6 VDD Power Supply Input 7 Sleep Logic input pin to enable product or Sleep Mode 8 NC No internal connection Leave unconnected 9 0g-Detect Linear Freefall digital logic output signal 10 g-Select Logic input pin to select g level 11 N/C Unused for factory trim Leave unconnected 12 N/C Unused for factory trim Leave unconnected 13 Self Test Input pin to initiate Self Test 14 N/C Unused for factory trim Leave unconnected 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 N/C XOUT ZOUT YOUT VSS VDD Sleep N/C 0g-Detect g-Select Self Test N/C N/C N/C Top View 2 3 4 3.3 nF 3.3 nF 3.3 nF 13 10 6 5 7Logic Input Logic Input Logic Input 0.1 μF VDD VDD VSS g-Select Self Test Sleep XOUT YOUT ZOUT MMA7361L 9 0g-Detect POWER SUPPLY VDD VSS Sleep g-Select 0g-Detect XOUT YOUT ZOUT Ac ce ler om et er VDD VSS VRH P0 P1 P2 A/DIN A/DIN A/DIN C C C C C C Mi cr oc on tro lle r C C Self Test P3 Sensors Freescale Semiconductor 5 MMA7361L Side View X OUT @ 0g = 1.65 V Y OUT @ +1g = 2.45 V Z OUT @ 0g = 1.65 V X OUT @ +1g = 2.45 V Y OUT @ 0g = 1.65 V Z OUT @ 0g = 1.65 V X OUT @ -1g = 0.85 V Y OUT @ 0g = 1.65 V Z OUT @ 0g = 1.65 V X OUT @ 0g = 1.65 V Y OUT @ -1g = 0.85 V Z OUT @ 0g = 1.65 V Direction of Earth's gravity field.* Top View X OUT @ 0g = 1.65 V Y OUT @ 0g = 1.65 V Z OUT @ -1g =0.85 V X OUT @ 0g = 1.65 V Y OUT @ 0g = 1.65 V Z OUT @ +1g = 2.45 V Top Top Bottom Bottom 123456 7 8 9 10 11 12 13 14 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 13 12 11 10 9 8 1 2 3 4 5 6 14 7 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 Top View Side View+Y -Y +X +Z-X -ZTo p B o tt o m : Arrow indicates direction of package movement.14-Pin LGA Package 123456 7 8 9 10 11 12 13 14 DYNAMIC ACCELERATION STATIC ACCELERATION * When positioned as shown, the Earth’s gravity will result in a positive 1g output. Sensors 6 Freescale Semiconductor MMA7361L Figure 7. MMA7361L Temperature Coefficient of Offset (TCO) and Temperature Coefficient of Sensitivity (TCS) Distribution Charts LSL USLTarget -2 -1 0 1 2 X-TCO mg/degC LSL USLTarget -2 -1 0 1 2 Y-TCO mg/degC LSL USLTarget -2 -1 0 1 2 Z-TCO mg/degC LSL USLTarget -0.01 -0.005 0 .005 .01 X-TCS %/degC LSL USLTarget -0.01 -0.005 0 .005 .01 Y-TCS %/degC LSL USLTarget -0.01 -0.005 0 .005 .01 Z-TCS %/degC Sensors Freescale Semiconductor 7 MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS MMA7361L PCB Mounting Recommendations MEMS based sensors are sensitive to Printed Circuit Board (PCB) reflow processes. For optimal zero-g offset after PCB mounting, care must be taken to PCB layout and reflow conditions. Reference application note AN3484 for best practices to minimize the zero-g offset shift after PCB mounting. 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. 6x2 12x1 14x0.9 14x0.6 10x0.8 1 13 6 8 Sensors 8 Freescale Semiconductor PACKAGE DIMENSIONS MMA7361L CASE 1977-01 ISSUE A 14-LEAD LGA Sensors Freescale Semiconductor 9 PACKAGE DIMENSIONS MMA7361L CASE 1977-01 ISSUE A 14-LEAD LGA Sensors 10 Freescale Semiconductor How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. 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