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document number: mma7368l rev 0, 05/2008 freescale semiconductor technical data ? freescale semiconductor, in c., 2008. all rights reserved. 1.5g three axis low-g micromachined accelerometer the mma7368l is a low power, low profile capacitive micromachined accelerometer featuring signal conditioning, a 1-pole low pass filter, temperature compensation, and self test . zero-g offset and sensitivity are factory set and require no external devices. the mma7368l 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 a ? sleep mode: 3 a ? low voltage operation: 2.2 v ? 3.6 v ? high sensitivity (800 mv/g @ 1.5g) ? fast turn on time (0.5 ms enable response time) ? self test for freefall detect diagnosis ? 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 sc roll, 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 mma7368lr2 ?40 to +85c 1977-01 lga-14 13? tape & reel mma7368l mma7368l: xyz axis accelerometer 1.5g 14 lead lga case 1977-01 bottom view figure 1. pin connections top view 1 2 3 4 5 6 7 8 9 10 11 12 13 14 n/c x out z out y out v ss v dd sleep n/c self test n/c n/c n/c n/c n/c
sensors 2 freescale semiconductor mma7368l figure 2. simplified accelerometer functional block diagram electro static discharge (esd) warning: this device is se nsitive to electrostatic discharge. although the freescale accelerometer contains internal 2000 v esd protection circuitr y, 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 ca using permanent damage.) rating symbol value unit maximum acceleration (all axis) g max 5000 g supply voltage v dd ?0.3 to +3.6 v drop test (1) 1. dropped onto concrete surface from any axis. d drop 1.8 m storage temperature range t stg ?40 to +125 c c to v converter x out y out z out oscillator clock gen sleep mode x-temp comp g-cell sensor gain + filter control logic nvm trim circuits y-temp comp z-temp comp v ss selftest selftest
sensors freescale semiconductor 3 mma7368l table 2. operating characteristics unless otherwise noted: -40c < t a < 85c, 2.2 v < v dd < 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 v dd i dd i dd t a g fs 2.2 ? ? -40 ? 3.3 400 3 ? 1.5 3.6 600 10 +85 ? v a a c g output signal zero-g (t a = 25c, v dd = 3.3 v) (5), (6) zero-g (4) sensitivity (t a = 25c, v dd = 3.3 v) 1.5g sensitivity (4) bandwidth response xy z v off v off , t a s 1.5g s,t a f -3dbxy f -3dbz 1.485 -2.0 740 -0.0075 ? ? 1.65 0.5 800 0.002 400 300 1.815 +2.0 860 +0.0075 ? ? v mg/c mv/g %/c hz hz self test output response x out , y out z out input low input high g stxy g stz v il v ih -0.05 +0.8 v ss 0.7 v dd -0.1 +1.0 ? ? ? +1.2 0.3 v dd v dd g g v v noise power spectral density rms (0.1 hz ? 1 khz) (4) n psd ? 350 ? g/ 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 t response t enable t st f gcellxy f gcellz f clk ? ? ? ? ? ? 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 (i out = 3 a) v fso v ss +0.1 ? v dd ?0.1 v nonlinearity, x out , y out , z out nl out -1.0 ? +1.0 %fso cross-axis sensitivity (10) v xy, xz, yz -5.0 ? +5.0 % 1. for a loaded output, the measurements are observed after an rc fi lter consisting of an internal resistor and an external 0.1 uf capacitor (recommended as a minimum to filter clock noi se) on the analog output for each axis and a 0.1 f capacitor on v dd - gnd. 2. these limits define the range of operation fo r 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 suppl y 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 accele ration the output will increase above v dd /2. for negative acceleration, the output will decrease below v dd /2. 6. for optimal 0g offset performance, adhere to an3484 and an3447 7. the response time between 10% of full scale v dd 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 acce leration applied 90 from the true axis of sensitivity. hz
sensors 4 freescale semiconductor mma7368l 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 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 mo ves with acceleration, the distance between the beams changes and each capacitor's value will change, (c = a /d). where a is the area of the beam, is the dielectric consta nt, 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 (s witched capacitor) the signal, providing a high level output vo ltage that is ratiometric and proportional to acceleration. figure 3. simplified transducer physical model special features 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 applicat ions such as hard disk drive protection where system integrit y must be ensured over the life of the product. customers can use self test to verify the solderability to confirm that th e 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- an d y-axis are deflected slightly while the z-axis is trimmed to deflect 1g. this procedure assures that both the mechani cal (g-cell) and electronic sections of the accelerometer are functioning. 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 a 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. becaus e 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 increa sed, the sensitiv ity and offset increase linearly; as supply voltage decreases, offset and sensitivity decrease linearly. this is a key feature when interfacing to a microcontrolle r or an a/d converter because it provides system level cancellation of supply induced errors in the analog to digital conversion process. acceleration
sensors freescale semiconductor 5 mma7368l basic connections pin descriptions figure 4. pinout description figure 5. accelerome ter with recommended connection diagram pcb layout figure 6. recommended pcb layout for interfacing accelerometer to microcontroller notes: 1. use 0.1 f capacitor on v dd 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 0.1uf 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. table 3. pin descriptions pin no. pin name description 1 n/c no internal connection leave unconnected 2x out x direction output voltage 3y out y direction output voltage 4z out z direction output voltage 5 v ss power supply ground 6v dd power supply input 7 sleep logic input pin to enable product or sleep mode 8 nc no internal connection leave unconnected 9 nc leave unconnected 10 nc leave unconnected 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 10 11 12 13 14 n/c x out z out y out v ss v dd sleep n/c self test n/c n/c n/c n/c n/c top view 2 3 4 0.1 f 0.1 f 0.1 f 13 6 5 7 logic input logic input 0.1 f v dd v dd v ss self test sleep x out y out z out mma7368l power supply v dd v ss sleep x out y out z out accelerometer v dd v ss v rh p0 a/d in a/d in a/d in c c c c c c microcontroller c c self test p1
sensors 6 freescale semiconductor mma7368l 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=1.65v 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 to p to p bottom bottom 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 13 12 11 10 9 8 12 34 56 14 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 top view side view +y -y +x +z -x -z to p bottom : arrow indicates direction of package movement. 14-pin lga package 1 2 3 4 5 6 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 freescale semiconductor 7 mma7368l figure 7. mma7368l temperature co efficient of offset (tco) and temperature coefficient of sensitivity (tcs) distribution charts ls l usl target -2 -1 0 1 2 x-tco mg/degc ls l usl target -2 -1 0 1 2 y-tco mg/degc ls l usl target -2 -1 0 1 2 z-tco mg/degc ls l usl target -0.01 -0.005 0 .005 .01 x-tcs %/degc ls l usl target -0.01 -0.005 0 .005 .01 y-tcs %/degc ls l usl target -0.01 -0.005 0 .005 .01 z-tcs %/degc
sensors 8 freescale semiconductor mma7368l minimum recommended footprint fo r surface mounted applications pcb mounting recommendations mems based sensors are sens itive 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 la yout 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 freescale semiconductor 9 mma7368l package dimensions case 1977-01 issue a 14-lead lga
sensors 10 freescale semiconductor mma7368l package dimensions case 1977-01 issue a 14-lead lga
mma7368l rev. 0 05/2008 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. technical information center, el516 2100 east elliot road tempe, arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.com/support 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) www.freescale.com/support japan: freescale semiconductor japan ltd. headquarters arco tower 15f 1-8-1, shimo-meguro, meguro-ku, tokyo 153-0064 japan 0120 191014 or +81 3 5437 9125 support.japan@freescale.com asia/pacific: freescale semiconductor hong kong ltd. technical information center 2 dai king street tai po industrial estate tai po, n.t., hong kong +800 2666 8080 support.asia@freescale.com for literature requests only: freescale semiconductor lite rature distribution center p.o. box 5405 denver, colorado 80217 1-800-441-2447 or 303-675-2140 fax: 303-675-2150 ldcforfreescalesemiconductor@hibbertgroup.com information in this document is provided solely to enable system and software implementers to use freescale semiconduc tor products. there are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. freescale semiconductor reserves the right to make changes without further notice to any products herein. freescale semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does freescale semiconductor assume any liability ar ising out of the application or use of any product or circuit, and specifically discl aims any and all liability, including without limitation consequential or incidental damages. ?typical? parameters that may be provided in freescale semiconductor data s heets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including ?typicals?, must be validated for each customer application by customer?s technical experts. freescale se miconductor does not convey any license under its patent rights nor the rights of others. freescale semiconductor products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the fa ilure of the freescale semiconductor product could create a situation where personal injury or death may occur. should buyer purchase or use freescale semiconductor products for any such unintended or unauthorized application, buyer shall indemni fy and hold freescale semiconductor and its officers, employees, subsidiaries, affili ates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that freescale semiconductor was negligent regarding the design or manufacture of the part. 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. 2008. all rights reserved. rohs-compliant and/or pb-free versions of freesc ale products have the functi onality and electrical characteristics of their non-rohs-compliant and/or non-pb-free counterparts. for further information, see http:/www.freescale.com or contact your freescale sales representative. for information on freescale?s environmental products program, go to http://www.freescale.com/epp.
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