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ADXL345BCCZ1 データシート(PDF) 7 Page - Analog Devices |
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ADXL345BCCZ1 データシート(HTML) 7 Page - Analog Devices |
7 / 24 page Preliminary Technical Data ADXL345 Rev. PrA | Page 7 of 24 FUNCTIONAL DESCRIPTION DEVICE OPERATION The ADXL345 is a complete three-axis acceleration measurement system with a selectable measurement range of either ±2 g, ±4 g, ±8 g, or ±16 g. It measures both dynamic acceleration resulting from motion or shock and static acceleration, such as gravity, which allows it to be used as a tilt sensor. The sensor is a polysilicon surface-micromachined structure built on top of a silicon wafer. Polysilicon springs suspend the structure over the surface of the wafer and provide a resistance against acceleration forces. Deflection of the structure is measured using differential capacitors that consist of independent fixed plates and plates attached to the moving mass. Acceleration deflects the beam and unbalances the differential capacitor, resulting in a sensor output whose amplitude is proportional to acceleration. Phase-sensitive demodulation is used to determine the magnitude and polarity of the acceleration. POWER SEQUENCING Power may be applied to VS or VDD I/O in any sequence without damaging the ADXL345. All possible power on states are summarized in Table 4. The interface voltage level is set with the interface supply voltage VDD I/O, which must be present to ensure that the ADXL345 does not create a conflict on the communications bus. For single-supply operation, VDD I/O can be the same as the main supply, VS. Conversely, in a dual-supply application, VDD I/O can differ from VS to accommodate the desired interface voltage. Once VS is applied, the device enters standby state, where power consumption is minimized and the device waits for VDD I/O to be applied and a command to enter measurement state (setting the MEASURE bit in the POWER_CTL register). Clearing the MEASURE bit returns the device to standby state. Table 4. Power Sequencing Condition VS VDD I/O Description Power Off Off Off Completely off, potential for communications bus conflict. Bus Enabled Off On No functions available, but will not create conflict on communications bus. Standby or Measurement On On At power up the device is in Standby mode awaiting a command to enter measurement mode and all sensor functions are off. Once instructed to enter Measurement mode, all sensor functions are available. POWER SAVING Power Modes The ADXL345 automatically modulates its power consumption proportionally with its output data rate as shown in Table 5. If additional power savings is desired, a lower power mode is available. In this mode, the internal sampling rate is reduced allowing for power savings in the 12.5 to 400Hz data rate range at the expense of slightly greater noise. To enter lower power mode, set the LOW_POWER bit(D4) in the BW_RATE register. Table 5. Current Consumption versus Data Rate Output Data Rate (Hz) Bandwidth (Hz) Rate Code IDD (µA) 3200 1600 1111 130 1600 800 1110 80 800 400 1101 130 400 200 1100 130 200 100 1011 130 100 50 1010 130 50 25 1001 80 25 12.5 1000 55 12.5 6.25 0111 37 6.25 3.125 0110 25 3.125 1.563 0101 25 1.563 0.782 0100 25 0.782 0.39 0011 25 0.39 0.195 0010 25 0.195 0.098 0001 25 0.098 0.048 0000 25 The current consumption in Low Power Mode is shown in Table 6. Cases where there is no advantage to using Low Power Mode are shaded. Table 6. Current Consumption versus Data Rate in Low Power Mode Output Data Rate Bandwidth (Hz) Rate Code IDD (µA) 3200 1600 1111 130 1600 800 1110 80 800 400 1101 130 400 200 1100 80 200 100 1011 55 100 50 1010 37 50 25 1001 30 25 12.5 1000 25 12.5 6.25 0111 25 6.25 3.125 0110 25 3.125 1.563 0101 25 1.563 0.782 0100 25 0.782 0.39 0011 25 0.39 0.195 0010 25 0.195 0.098 0001 25 0.098 0.048 0000 25 |
同様の部品番号 - ADXL345BCCZ1 |
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同様の説明 - ADXL345BCCZ1 |
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