document number: MMA2260d rev 3, 03/2006 freescale semiconductor technical data ? freescale semiconductor, in c., 2006. all rights reserved. 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. zero- g offset full scale span and filter cut-of f are factory set and require no external devices. a full system self-test capa bility 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 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 temperature range case no. package MMA2260d ?40 to +105 c 475-01 soic-16 MMA2260dr2 ?40 to +105 c 475-01 soic-16, tape & reel MMA2260eg ?40 to +105 c 475-01 soic-16 MMA2260egr2 ?40 to +105 c 475-01 soic-16, tape & reel MMA2260 MMA2260d: x axis sensitivity micromachined accelerometer 1.5g d suffix eg suffix (pb-free) 16-lead soic case 475-01 figure 1. simplified acceleromet er functional block diagram v ss v ss v ss v out status v dd st n/c n/c n/c n/c n/c n/c n/c n/c 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 figure 2. pin connections g-cell sensor integrator gain filter temp comp and gain self-test control logic & eprom trim circuits clock generator oscillator v dd v out v ss st status
sensors 2 freescale semiconductor MMA2260d electro static discharge (esd) warning: this device is se nsitive 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. table 1. maximum ratings (1) (maximum ratings are the limits to which the device can be exposed without ca using permanent damage.) 1. dropped onto concrete surface from any axis. rating symbol value unit unpowered acceleration (all axes) g upd 2000 g supply voltage v dd -0.3 to +7.0 v drop test (1) h drop 1.2 m storage temperature range t stg -40 to +125 c
sensors freescale semiconductor 3 MMA2260d table 2. operating characteristics (unless otherwise noted: ?40 c t a +105 c, 4.75 v dd 5.25, acceleration = 0g, loaded output (1) ) 1. for a loaded output the measurements are observ ed after an rc filter consisting of a 1 k ? resistor and a 0.1 f capacitor to ground. characteristic symbol min typ max unit operating range (2) supply voltage (3) supply current operating temperature range acceleration range 2. these limits define the range of operation fo r which the part will meet specification. 3. within the supply range of 4.75 and 5.25 volts, the device opera tes 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. v dd i dd t a g fs 4.75 1.1 ?40 ? 5.00 2.2 ? 1.5 5.25 3.2 +105 ? v ma c g output signal zero g (v dd = 5.0 v) (4) sensitivity (t a = 25 c, v dd = 5.0 v) (5) sensitivity (v dd = 5.0 v) (5) bandwidth response nonlinearity 4. the device can measure both + and ? acceleration. with no i nput acceleration the output is at midsupply. for positive accele ration the output will increase above v dd /2 and for negative acceleration the output will decrease below v dd /2. 5. sensitivity limits apply to 0 hz acceleration. v off s s f ?3db nl out 2.3 1140 1110 40 ?1.0 2.5 1200 1200 50 ? 2.7 1260 1290 60 +1.0 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) 6. at clock frequency ? 34 khz. n rms n sd ? ? 3.5 350 ? ? mvrms g/ hz self-test output response (v dd = 5.0 v) input low input high input loading (7) response time (8) 7. the digital input pin has an internal pull -down current source to prevent inadvertent self test initiation due to external bo ard level leakages. 8. time for the output to reach 90% of its final value after a self-test is initiated. ? v st v il v ih i in t st 0.3 v ss 0.7 v dd ?50 ? 0.4 ? ? ?125 20 0.5 0.3 v dd v dd ?300 25 v v v a ms status (9)(10) output low (i load = 100 a) output high (i load = ?100 a) 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. t he 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. v ol v oh ? v dd ?0.8 ? ? 0.4 ? v v output stage performance electrical satura tion recovery time (11) full scale output range (i out = ?200 a) capacitive load drive (12) output impedance 11. time for amplifiers to recover after an acceleration signal causes them to saturate. 12. preserves phase margin (60 ) to guarantee output amplifier stability. t delay v fso c l z o ? v ss +0.25 ? ? ? ? ? 50 2.0 v dd ?0.25 100 ? ms v pf ? mechanical characteristics transverse sensitivity (13) 13. a measure of the device's ability to reject an acceleration applied 90 from the true axis of sensitivity. v yx,zx ??5.0% fso
sensors 4 freescale semiconductor MMA2260d 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 = na /d). where a is the ar ea 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. 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. self-test the sensor provides a self-t est feature that allows the verification of the mechanical and electrical integrity of the accelerometer at any ti me before or after in stallation. 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 av 2 /d 2 ) causes the center plate to deflect. the resultant deflection is measured by the accelerometer's control asic and a proportional ou tput 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 pi n 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
sensors freescale semiconductor 5 MMA2260d basic connections pinout description . figure 5. soic accelerometer with recommended connection diagram pcb layout figure 6. recommended pcb layout for interfacing accelerometer to microcontroller notes: 1. use a 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 an rc filter of 1 k ? and 0.01 f on the output of the accelerometer to minimi ze 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. this will prevent aliasing errors. table 3. pin description pin no. pin name description 1 thru 3 v ss redundant connections to the internal v ss and may be left unconnected. 4 v out output voltage of the accelerometer. 5 status logic output pin to indicate fault. 6 v dd the power supply ground. 7 v ss the power supply input. 8 st logic input pin used to initiate self-test. 9 thru 13 trim pins used for factory trim. leave unconnected. 14 thru 16 ? no internal connection. leave unconnected. v ss v ss v ss v out status v dd st n/c n/c n/c n/c n/c n/c n/c n/c 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 8 MMA2260d st v out output signal r1 1 k ? 4 c2 0.01 f 7 logic input v dd c1 0.1 f 5 status 6 v dd v ss p0 a/d in v rh v ss v dd st v out v ss v dd 0.01 f 1 k ? 0.1 f 0.1 f power supply 0.1 f p1 status microcontroller accelerometer c c c r c
sensors 6 freescale semiconductor MMA2260d 1. when positioned as shown, the earth's gravity will result in a positive 1g output direction of earth's gravity field. (1) static acceleration +1g -1g 0g 0g v out = 2.50v v out = 2.50v v out = 3.7v v out = 1.3v 16-pin soic package +x -x top view 10 11 12 13 14 15 16 8 7 6 5 4 3 2 1 9 dynamic acceleration
sensors freescale semiconductor 7 MMA2260d package dimensions case 475-01 issue c 16-lead soic page 1 of 2
sensors 8 freescale semiconductor MMA2260d package dimensions case 475-01 issue c 16-lead soic page 2 of 2
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