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Inside Freescale Sensor Products

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Freescale Semiconductor is a leading company in the field of electronic sensors, offering a wide and complete family of acceleration, pressure, and proximity sensors. With over 25 years of experience in the sensors design and manufacturing, with more than 750 million MEMS-based sensors delivered, Freescale Semiconductor meets the customers’ demand for sensor solutions

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Inside Freescale Sensor Products

  1. 1. Published on Your Electronics Open Source (http://dev.emcelettronica.com) Home > Blog > slovati's blog > Contenuti Inside Freescale Sensor Products By slovati Created Mar 26 2009 - 07:08 Freescale Semiconductor is a leading company in the field of electronic sensors, offering a wide and complete family of acceleration, pressure, and proximity sensors. With over 25 years of experience in the sensors design and manufacturing, with more than 750 million MEMS-based sensors delivered, Freescale Semiconductor meets the customers? demand for sensor solutions. Acceleration sensors [1] The acceleration sensors offered by Freescale Semiconductor are all MEMS (Micro Mechanical Electrical Systems) based and are suitable for the measurement of change in forces associated to tilt, fall, motion, vibration, shock, and positioning. The devices are able to measure accelerations from 1.5g up to 200g, and can have single, dual, or triple axis sensing capability (X, XY, XYZ, or Z axis of sensitivity). Accelerometers are composed of two units located on the same chip (as shown in the following picture): g-cell (the acceleration transducer): it is a micromachined capacitive sensing unit composed of many beams connected to a central mass which can freely move between them. The acceleration applied to the sensor moves the g-cell modifying its capacitance. The g-cell is hermetically sealed on the wafer layer, thus making a robust and reliable sensor. The g-cell is designed so that its resonant frequency is much higher than the cut-off frequency of the internal low-pass filter: in this way, the resonant frequency does not affect the accelerometer response. control IC (a CMOS ASIC): its function is to measure the g-cell capacitance variations and compute the corresponding acceleration value. Other tasks performed by this chip are: signal amplification, signal conditioning, low pass filtering (a 4-pole switched capacitor filter with a Bessel implementation), and temperature compensation. The output signal produced by the control IC is ratiometric and proportional to the acceleration. These sensors are very fast, with low power consumption and low supply voltage. They can be divided into analog and digital sensors. Analog sensors are normally interfaced with analog to digital converters (ADC),
  2. 2. often integrated on many microcontrollers. For this purpose, their output has a 2.5V offset so that positive and negative acceleration can be measured. The output DC offset can also be modified according to the customers? need. Digital sensors are available with an I2C or SPI interface. Acceleration sensors have also a self-test function which verifies the electrical and mechanical integrity of the sensor; this feature can be activated either prior or after the device installation and it is suitable for critical applications such as airbag systems. Freescale accelerometers provide also a status pin which signals a fault condition such as: supply voltage below the low voltage detection threshold (LVD), clock oscillator failure, and internal EPROM parity error. The fault latch can be reset by issuing a self-test procedure: nevertheless, it will be asserted again when at least one of the above conditions is met. Typical applications of acceleration sensors are as follows: automotive field: airbags, crash detectors, fuel shut-off valve (occurs when a crash condition is detected), braking systems, tire pressure monitoring system (TPMS), stability control systems industrial and consumer field: gaming, HDD protection, GPS dead reckoning, MP3 players, image stabilization, navigation systems, e-compass, motion sensing healthcare and fitness field: pedometers, rehabilitation equipments, sports medicine and diagnostics systems Pressure sensors [2] Freescale Semiconductor?s provides a wide range of pressure sensors; all the devices are MEMS-based, with a silicon micromachined and electromechanical structure. The sensors family provides devices able to measure pressure up to 150 psi (1000 KPa) including both positive and negative pressure, with temperature compensation, calibration, and signal conditioning features. They can be grouped into three main categories: differential: pressure is applied to both the opposite sides of the wafer sensing element (P1 and P2 in the following picture), and the difference in pressure between the two points is measured by the sensor gauge: on the upper side of the sensor is applied the pressure (P1 in the following picture), whereas the bottom side is left at the ambient atmospheric pressure absolute: pressure is applied to the upper side of the sensor, whereas the bottom side is vacuum- sealed inside the reference chamber of the die during manufacturing, with a zero-pressure reference value (see next picture)
  3. 3. Typical applications of pressure sensors are as follows: automotive and avionics field: air speed indicator, air flow measurement, altimeter, ejection seat control, oil pressure sensor, fuel level indicator, suspension system, tire pressure monitoring system industrial and consumer field: barometers, flow rate indicator, balancing, robotics, air and water filtering systems healthcare and fitness field: blood pressure, heart monitor, kidney dialysis, blood gas and serum analysis Proximity sensors [3] Proximity sensors are used in applications where non-contact sensing of objects is requested. They are especially intended for small or simple interfaces where just few controls (or ?touchbuttons?) are involved. Freescale Semiconductor has recently announced a new series of proximity capacitive touch sensor controllers with an I2C interface: the MPR031 and MPR032. MPR03X are designed to operate either with two electrodes (touch panels) and IRQ enabled, or three electrodes and IRQ disabled. Average supply voltage is very low (about 8 ?A) thus allowing a very long life even for small batteries. These devices have very compact dimensions: 2 x 2 x 0.65 mm in dual flat no lead (DFN) 8-pin package and they require only an external 75 K? resistor (with a 1% tolerance). Typical applications for the MPR03X devices are: mobile phones, multimedia players, Bluetooth headsets, remote control, PC peripherals, lighting controls, watch and alarm clock, table lamps, dimmers, and electronic products. The I2C interface allows communication with a host controller at a maximum data rate of 400 kbps, whereas the I2C addresses are fixed and set to 0x4A (MPR031) and 0x4B (MPR032). Using both MPR03X in the same circuit allows to achieve 4-6 electrodes, depending whether the IRQ pin is used or not. When it is used, the IRQ pin signals to host controller a change in the electrode status (it can be either a touch or release action); the host controller can then acquire the electrode status by reading the associated register on the device. MPR03X have a built-in calibration feature which continually adjust the baseline capacitance of each electrode; the host controller has only to set the delta thresholds related to the touch and release events. Read the Italian version: La famiglia di sensori Freescale [4] CONTACT REQUEST If you want to know more about this Freescale product, please submit your request to Arrow Italy using this form
  4. 4. . [5] NOTE: this form is valid ONLY for Companies or Customers based in Italy and working in the Italian area. Hardware pressure proximity sensor Trademarks Source URL: http://dev.emcelettronica.com/inside-freescale-sensor-products Links: [1] http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=0112691118&tid=rspf [2] http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=0112699036&tid=rspf [3] http://www.freescale.com/webapp/sps/site/taxonomy.jsp?nodeId=0112698268&tid=rspf [4] http://it.emcelettronica.com/la-famiglia-di-sensori-freescale [5] http://it.emcelettronica.com/contact/freescale