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Freescale Semiconductor Technical Data
MMA3204KEG Rev 0, 11/2009
Surface Mount Micromachined Accelerometer
The MMA3204 series of dual axis (X and Y) silicon capacitive, micromachined accelerometers features signal conditioning, a 4-pole low pass filter and temperature compensation and separate outputs for the two axes. 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. Features * Sensitivity in two separate axes: 100g X-axis and 30g Y-axis * Integral Signal Conditioning * Linear Output * Ratiometric Performance * 4th Order Bessel Filter Preserves Pulse Shape Integrity * Calibrated Self-test * Low Voltage Detect, Clock Monitor, and EPROM Parity Check Status * Transducer Hermetically Sealed at Wafer Level for Superior Reliability * Robust Design, High Shocks Survivability * Qualified AEC-Q100, Rev. F Grade 2 (-40C/ +105C) Typical Applications * Vibration Monitoring and Recording * Impact Monitoring * Appliance Control * Mechanical Bearing Monitoring * Computer Hard Drive Protection * Computer Mouse and Joysticks * Virtual Reality Input Devices * Sports Diagnostic Devices and Systems ORDERING INFORMATION
Device MMA3204EG MMA3204EGR2 MMA3204KEG* MMA3204KEGR2* Temperature Range -40 to +125C -40 to +125C -40 to +125C -40 to +125C Case No. 475A-02 475A-02 475A-02 475A-02 Package SOIC-20 SOIC-20, Tape & Reel SOIC-20 SOIC-20, Tape & Reel
MMA3204KEG
MMA3204KEG: XY-AXIS SENSITIVITY MICROMACHINED ACCELEROMETER 100/30g
KEG SUFFIX (Pb-FREE) 20-LEAD SOIC CASE 475A-02
*Part number sourced from a different facility.
AVDD
VDD
N/C N/C N/C N/C ST XOUT
1 2 3 4 5 6 7 8 9 10
20 19 18 17 16 15 14 13 12 11
GND N/C N/C N/C N/C N/C N/C N/C N/C YOUT
G-Cell Sensor
Integrator
Gain
Filter
Temp
XOUT YOUT
ST
Self-Test
Control Logic & EPROM Trim Circuits
Oscillator
Clock Gen.
VSS
STATUS VSS VDD AVDD
Status
Figure 1. Simplified Accelerometer Functional Block Diagram
Figure 2. Pin Connections
(c) Freescale Semiconductor, Inc., 2009. All rights reserved.
Table 1. Maximum Ratings (Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating Powered Acceleration (all axes) Unpowered Acceleration (all axes) Supply Voltage Drop Test (1) Storage Temperature Range NOTES:
1. Dropped onto concrete surface from any axis.
Symbol Gpd Gupd VDD Ddrop Tstg
Value 1500 2000 -0.3 to +7.0 1.2 -40 to +125
Unit g g V m C
ELECTRO STATIC DISCHARGE (ESD)
WARNING: This device is sensitive 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.
MMA3204KEG 2 Sensors Freescale Semiconductor
Table 2. Operating Characteristics (Unless otherwise noted: -40C TA +105C, 4.75 VDD 5.25, Acceleration = 0g, Loaded output.(1))
Characteristic Operating Range Supply Voltage Supply Current Operating Temperature Range Acceleration Range X-axis Acceleration Range Y-axis Output Signal Zero g X-axis (TA = 25C, VDD = 5.0 V)(4) Zero g Y-axis (TA = 25C, VDD = 5.0 V)(4) Zero g X-axis Zero g Y-axis Sensitivity X-axis (TA = 25C, VDD = 5.0 V)(5) Sensitivity Y-axis (TA = 25C, VDD = 5.0 V)(5) Sensitivity X-axis Sensitivity Y-axis Bandwidth Response Nonlinearity Noise RMS (.01 Hz - 1 kHz) Power Spectral Density Clock Noise (without RC load on output)(6) Self-Test Output Response Input Low Input High Input Loading(7) Response Time(8) Status(12)(13) Output Low (Iload = 100 A) Output High (Iload = 100 A) Minimum Supply Voltage (LVD Trip) Clock Monitor Fail Detection Frequency Output Stage Performance Electrical Saturation Recovery Time(9) Full Scale Output Range (IOUT = 200 A) Capacitive Load Drive(10) Output Impedance Mechanical Characteristics Transverse Sensitivity(11) Package Resonance NOTES:
1. For a loaded output the measurements are observed after an RC filter consisting of a 1 k resistor and a 0.01 F capacitor to ground.
(2) (3)
Symbol VDD IDD TA gFS gFS VOFF VOFF VOFF,V VOFF,V S S SV SV f-3dB NLOUT nRMS nPSD nCLK gST VIL VIH IIN tST VOL VOH VLVD fmin tDELAY VFSO CL ZO VXZ,YZ fPKG
Min 4.75 6 -40 -- -- 2.35 2.25 0.46 VDD 0.44 VDD 19 63.33 3.72 12.40 360 -1.0 -- -- -- 9.6 VSS 0.7 x VDD -30 -- -- VDD -0.8 2.7 50 -- 0.25 -- -- -- --
Typ 5.00 8 -- 112.5 33.75 2.5 2.5 0.50 VDD 0.50 VDD 20 66.67 4 13.33 400 -- -- 110 2.0 12 -- -- -100 2.0 -- -- 3.25 -- 0.2 -- -- 300 -- 10
Max 5.25 10 +125 -- -- 2.65 2.75 0.54 VDD 0.56 VDD 21 70.0 4.28 14.27 440 +1.0 3.5 -- -- 14.4 0.3 x VDD VDD -300 - 0.4 -- 4.0 260 -- VDD - 0.25 100 -- 5.0 --
Unit V mA C g g V V V V mV/g mV/g mV/g/V mV/g/V Hz % FSO mVrms V/(Hz1/2) mVpk g V V A ms V V V kHz ms V pF % FSO kHz
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 mid-supply. For positive acceleration the output will increase above VDD/2 and for negative acceleration the output will decrease below VDD/2. 5. The device is calibrated at 20g. 6. At clock frequency 70 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, as a means to check the connectivity of the self-test and Status pins in the application. 13. The Status pin output latches high if a Low Voltage Detection or Clock Frequency failure occurs, or the EPROM parity changes to odd. The Status pin can be reset low if the self-test pin is pulsed with a high input for at least 100 s, unless a fault condition continues to exist.
MMA3204KEG Sensors Freescale Semiconductor 3
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 move between fixed beams. The movable beams can be deflected from their rest position by subjecting the system to an acceleration (Figure 2). 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 2). 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 area of the facing side of the beam, is the dielectric constant, D is the distance between the beams, and N is the number of beams. The X-Y device contains two structures at right angles to each other. 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. Acceleration
Figure 2. Simplified Transducer Physical Model
SPECIAL FEATURES
Filtering The Freescale accelerometers contain an onboard 4-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. 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 automotive airbag systems where system integrity must be ensured over the life of the vehicle. A fourth "plate'' is used in the g-cell as a selftest plate. When the user applies a logic high input to the selftest 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. Ratiometricity Ratiometricity simply means that the output offset voltage and sensitivity will scale linearly with applied supply voltage. That is, as you increase supply voltage 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. Status Freescale 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 one (or more) of the following events occur:
* * *
Supply voltage falls below the Low Voltage Detect (LVD) voltage threshold Clock oscillator falls below the clock monitor minimum frequency 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.
MMA3204KEG 4 Sensors Freescale Semiconductor
BASIC CONNECTIONS
Pinout Description PCB Layout
P1 P0 R A/D In Microcontroller
N/C N/C N/C N/C ST XOUT STATUS VSS VDD AVDD
1 2 3 4 5 6 7 8 9 10
20 19 18 17 16 15 14 13 12 11
GND N/C N/C N/C N/C N/C N/C N/C N/C YOUT
STATUS Accelerometer ST XOUT
1 k C 0.01 F
YOUT VSS VDD
VSS
R 1 k C 0.1 F
A/D In
C 0.01 F
C
VDD
0.1 F
VRH
C 0.1 F
Power Supply Pin No. 1 thru 3 4 5 6 7 8 9 10 11 12 thru 16 17 thru 19 20 Pin Name -- -- ST XOUT STATUS VSS VDD AVDD YOUT -- -- GND Description Leave unconnected. No internal connection. Leave unconnected. Logic input pin used to initiate self-test. Output voltage of the accelerometer. X Direction. Logic output pin to indicate fault. The power supply ground. The power supply input. Power supply input (Analog). Output voltage of the accelerometer. Y Direction. Used for factory trim. Leave unconnected. No internal connection. Leave unconnected. Ground.
Figure 4. Recommended PCB Layout for Interfacing Accelerometer to Microcontroller NOTES: * Use a 0.1 F capacitor on VDD to decouple the power source. * 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 of the open ended terminals shown in Figure 4. * Use an RC filter of 1 k and 0.01 F 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.
VDD Logic Input C1 0.1 F 5 9 10 8
MMA3204KEG ST VDD AVDD VSS YOUT XOUT
7 R1 1 k
Status
6
X Output Signal
C2 0.01 F 11 R2 1 k Y Output Signal
C3 0.01 F
Figure 3. SOIC Accelerometer with Recommended Connection Diagram
MMA3204KEG Sensors Freescale Semiconductor 5
Dynamic Acceleration Sensing Direction
+Y
N/C N/C N/C N/C
1 2 3 4 5 6 7 8 9 10
20 19 18 17 16 15 14 13 12 11
GND N/C N/C N/C N/C N/C N/C N/C N/C YOUT
Acceleration of the package in the +X and +Y direction (center plates move in the -X and -Y direction) will result in an increase in the X and Y outputs.
+X
ST XOUT STATUS VSS VDD AVDD
-X
Activation of Self test moves the center plates in the -X and -Y direction, resulting in an increase in the X and Y outputs.
-Y 20-Pin SOIC Package
N/C pins are recommended to be left FLOATING
Top View
Static Acceleration Sensing Direction
10 9
87
6
54
3
2
1
Direction of Earth's gravity field.*
11 12 13 14 15 16 17 18 19 20
Front View
Side View
* When positioned as shown, the Earth's gravity will result in a positive 1g output in the X channel.
MMA3204KEG 6 Sensors 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.
0.050 in. 1.27 mm
0.380 in. 9.65 mm
0.024 in. 0.610 mm
0.080 in. 2.03 mm
Figure 5. Footprint SOIC-20 (Case 475A-02)
MMA3204KEG Sensors Freescale Semiconductor 7
PACKAGE DIMENSIONS
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CASE 475A-02 ISSUE C 20-LEAD SOIC
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PACKAGE DIMENSIONS
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CASE 475A-02 ISSUE C 20-LEAD SOIC
MMA3204D Sensors Freescale Semiconductor 9
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MMA3204KEG Rev. 0 11/2009

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