MMA6231QR2

Freescale Semiconductor Technical Data Document Number: MMA6231Q Rev 2, 10/2006 ±10g Dual Axis Micromachined Accelerometer The MMA6200 series of low cost capacitive micromachined accelerometers feature signal conditioning, a 1-pole low pass filter and temperature compensation. 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 • • • • • • • • • • Low Noise Low Cost Low Power 2.7 V to 3.6 V Operation 6mm x 6mm x 1.98 mm QFN Integral Signal Conditioning with Low Pass Filter Linear Output Ratiometric Performance Self-Test Robust Design, High Shocks Survivability MMA6231Q MMA6233Q MMA6230Q Series: X-Y AXIS SENSITIVITY MICROMACHINED ACCELEROMETER ± 10 g Bottom View Typical Applications • • • • • • • Pedometer Appliance Control Impact Monitoring Vibration Monitoring and Recording Position & Motion Sensing Freefall Detection Smart Portable Electronics 16-LEAD QFN CASE 1477-02 Top View XOUT YOUT N/C ORDERING INFORMATION Device Name MMA6231Q MMA6231QR2 MMA6233Q MMA6233QR2 Bandwidth Response 300 Hz 300 Hz 900 Hz 900 Hz NC 1 2 3 4 16 15 14 13 12 ST 11 N/C 10 N/C 9 N/C IDD 1.2 mA 1.2 mA 2.2 mA 2.2 mA Case No. 1477-02 1477-02 1477-02 1477-02 Package QFN-16, Tube QFN-16,Tape & Reel QFN-16, Tube QFN-16,Tape & Reel NC VDD VSS 5 N/C 6 N/C 7 N/C Figure 1. Pin Connections © Freescale Semiconductor, Inc., 2006. All rights reserved. N/C N/C 8 G-Cell Sensor X-Integrator X-Gain X-Filter X-Temp Comp VDD XOUT ST Self Test Control Logic & EEPROM Trim Circuits Oscillator Clock Generator Y-Integrator Y-Gain Y-Filter Y-Temp Comp YOUT 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 Maximum Acceleration (all axis) Supply Voltage Drop Test(1) Storage Temperature Range 1. Dropped onto concrete surface from any axis. Symbol gmax VDD Ddrop Tstg Value Unit g V m °C ±2000 –0.3 to +3.6 1.2 –40 to +125 ELECTRO STATIC DISCHARGE (ESD) WARNING: This device is sensitive to electrostatic discharge. Although the Freescale accelerometers contain internal 2 kV 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. MMA6231Q 2 Sensors Freescale Semiconductor Table 2. Operating Characteristics Unless otherwise noted: -20°C < TA < 85°C, 3.0 V < VDD < 3.6 V, Acceleration = 0g, Loaded output (1) Characteristic Operating Range (2) Symbol VDD IDD IDD TA gFS VOFF VOFF, TA S S, TA f_3dB f_3dB NLOUT nRMS nRMS nPSD nPSD gST VIL VIH RPO tST VFSO CL ZO tRESPONSE tRESPONSE VZX, YX, ZY Min 2.7 — — –20 — 1.485 — 111 — — — –1.0 — — — — 2.0 — 0.7 VDD 43 — VSS +0.25 — — — — –5.0 Typ 3.3 1.2 2.2 — 10 1.65 2.0 120 0.015 300 900 — 0.7 0.6 50 30 — — — 57 2.0 — — 50 2.0 0.7 — Max 3.6 1.5 3.0 +85 — 1.815 — 129 — — — +1.0 — — — — — 0.3 VDD VDD 71 — VDD –0.25 100 300 — — +5.0 Unit V mA mA °C g V mg/°C mV/g %/°C Hz Hz % FSO mVrms Supply Voltage(3) Supply Current MMA6231Q MMA6233Q Operating Temperature Range Acceleration Range Output Signal Zero g (TA = 25°C, VDD = 3.3 V)(4) Zero g Sensitivity (TA = 25°C, VDD = 3.3 V) Sensitivity Bandwidth Response MMA6231Q MMA6233Q Nonlinearity Noise MMA6231Q RMS (0.1 Hz – 1 kHz) MMA6233Q RMS (0.1 Hz – 1 kHz) Power Spectral Density RMS (0.1 Hz – 1 kHz) MMA6231Q MMA6233Q Self-Test Output Response Input Low Input High Pull-Down Resistance(5) Response Time(6) Output Stage Performance Full-Scale Output Range (IOUT = 200 µA) Capacitive Load Drive(7) Output Impedance Power-Up Response Time MMA6231Q MMA6233Q Mechanical Characteristics Transverse Sensitivity(8) ug/√Hz g V V kΩ ms V pF Ω ms ms % FSO 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 to ground. 2. These limits define the range of operation for which the part will meet specification. 3. Within the supply range of 2.7 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. 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. 5. The digital input pin has an internal pull-down resistance to prevent inadvertent self-test initiation due to external board level leakages. 6. Time for the output to reach 90% of its final value after a self-test is initiated. 7. Preserves phase margin (60°) to guarantee output amplifier stability. 8. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity. MMA6231Q 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 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 plates form two back-to-back capacitors (Figure 4). As the center plate moves with acceleration, the distance between the plates changes and each capacitor's value will change, (C = Aε/D). Where A is the area of the plate, ε is the dielectric constant, and D is the distance between the plates. 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. SPECIAL FEATURES Filtering These Freescale accelerometers contain 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. Self-Test The sensor provides a self-test feature allowing the verification of the mechanical and electrical integrity of the accelerometer at any time before or after installation. A fourth plate is used in the g-cell as a self-test plate. When a logic high input to the self-test pin is applied, 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 ASIC and a proportional output voltage results. This procedure assures both the mechanical (g-cell) and electronic sections of the accelerometer are functioning. Freescale accelerometers include fault detection circuitry and a fault latch. Parity of the EEPROM bits becomes odd in number. Self-test is disabled when EEPROM parity error occurs. 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 Figure 3. Transducer Physical Model Figure 4. Equivalent Circuit Model MMA6231Q 4 Sensors Freescale Semiconductor BASIC CONNECTIONS Pinout Description PCB Layout Top View XOUT YOUT N/C N/C ST Accelerometer XOUT YOUT VSS VDD R 1 kΩ R 1 kΩ C 0.1 µF C C 0.1 µF P0 Microcontroller A/D IN A/D IN 0.1 µF 16 15 NC NC VDD VSS 1 2 3 4 5 N/C 6 N/C 14 13 12 ST 11 N/C 10 N/C 9 N/C 7 N/C 8 N/C VSS C 0.1 µF VDD VRH C 0.1 µF Figure 4. Pinout Description Pin No. 1, 5–7, 13, 16 14 15 3 4 2, 8–11 12 Pin Name N/C YOUT XOUT VDD VSS N/C ST Description No internal connection. Leave unconnected. Output voltage of the accelerometer. Y Direction. Output voltage of the accelerometer. X Direction. Power supply input. The power supply ground. Used for factory trim. Leave unconnected. Logic input pin used to initiate self-test. Power Supply Figure 6. Recommend 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. Flag underneath package is connected to ground. 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. VDD 3 0.1 µF 4 12 VSS VDD MMA6200Q Series YOUT 14 1 kΩ 0.1 µF X Output Signal 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 (16 kHz for Low IDD and 52 kHz for Standard IDD for the sampling frequency). This will prevent aliasing errors. 9. PCB layout should not run traces or vias under the QFN part. This could lead to ground shorting to the accelerometer flag. Logic Input XOUT 15 ST 1 kΩ 0.1 µF Y Output Signal Figure 5. Accelerometer with Recommended Connection Diagram MMA6231Q Sensors Freescale Semiconductor 5 DYNAMIC ACCELERATION Top View +Y 16 1 15 14 13 12 11 10 9 5 6 7 8 +X 2 3 4 –X –Y 16-Pin QFN Package STATIC ACCELERATION Top View Direction of Earth’s gravity field(1) XOUT @ 0g = 1.65 V YOUT @ -1g = 1.53 V XOUT @ +1g = 1.77 V YOUT @ 0g = 1.65 V XOUT @ -1g = 1.53 V YOUT @ 0g = 1.65 V XOUT @ 0g = 1.65 V YOUT @ +1g = 1.77 V 1. When positioned as shown, the Earth’s gravity will result in a positive 1g output. MMA6231Q 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. 6.0 0.55 12 4.25 9 13 6.0 8 1.00 1 4 Flag Solder areas Non-Solder areas 5 0.50 Pin 1 ID (non metallic) 16 MMA6231Q Sensors Freescale Semiconductor 7 PACKAGE DIMENSIONS PAGE 1 OF 3 CASE 1477-02 ISSUE B 16-LEAD QFN MMA6231Q 8 Sensors Freescale Semiconductor PACKAGE DIMENSIONS PAGE 2 OF 3 CASE 1477-02 ISSUE B 16-LEAD QFN MMA6231Q Sensors Freescale Semiconductor 9 PACKAGE DIMENSIONS PAGE 3 OF 3 CASE 1477-02 ISSUE B 16-LEAD QFN MMA6231Q 10 Sensors Freescale Semiconductor How to Reach Us: Home Page: www.freescale.com E-mail: support@freescale.com USA/Europe or Locations Not Listed: Freescale Semiconductor Technical Information Center, CH370 1300 N. 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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. 2005. All rights reserved. MMA6231Q Rev. 2 10/2006