The equivalent capacitance combines with the input or shunting resistance of subsequent amplifying or buffering circuitry to create a single-pole high-pass filter (HPF).
This capacitive coupling of the voltage source explains why the device cannot provide steady-state inclination measurements. (Other reactive elements contribute second-order effects that are not material to this analysis.) The typical capacitance ranges from a few hundred picofarads to several nanofarads.
A piezo transducer’s equivalent circuit is an ac voltage source in series with a capacitor. In these short-term acceleration applications, a piezo-bender or piezo film sensor is the transducer of choice. But in real-world applications, it’s generally a short-term transitory phenomenon. Acceleration can also theoretically be steady state. Inclination measurements can be thought of as “dc” or steady-state measurements. Price for a QFN packaged device is USD 0.98 (3 000 pcs).Accelerometers are used in instrumentation applications to measure a change in velocity with respect to time or an inclination (the angle between an object’s vertical axis and a line perpendicular to a plane tangent to the earth’s surface).
The MAS6250 is available in QFN-16 3x3x0.75 mm package. When not used the device enters shut down operating mode (typ 0.11uA) to save power. The LED current is adjustable by external resistor. The LED driver supports use of pulse-width modulation (PWM) dimming control and is capable of driving up to 15mA current. In addition to multi-tone sound the device supports single-tone sound which frequency is adjustable by external resistor. The bridge-tied load (BTL) output of the piezo driver is capable of driving up to 35Vpp signal in a very wide supply voltage range from 1.2V to 5.5V. The output voltage is regulated and adjustable up to 17.5V by external resistors. The heart of the IC is a high efficiency synchronous boost DC/DC converter requiring only a small 0806 sized 2.2mH inductor. The MAS6250 includes LED driver which offers additional area and cost saving in many applications using LEDs. Typical applications include piezo buzzers, various alarm products, white goods and handheld or portable devices with sound feature. It is a high efficiency, easy to use and low cost solution for piezo sound applications requiring high sound pressure level (SPL). Micro Analog Systems Oy introduces combined piezo and LED driver IC in a small QFN-16 3x3x0.75 mm package. MAS6250 – Piezo and LED Driver IC for Multi-Tone Sound
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