介绍：
The ADXL345 is a small, thin, ultralow power, 3-axis accelerometer with high resolution (13-bit) measurement at up to ±16 g. Digital output data is formatted as 16-bit twos complement（ 二进制补码） and is accessible（存取） through either a SPI (3- or 4-wire) or I2C digital interface.
The ADXL345 is well suited for mobile device applications. It measures the static acceleration of gravity in tilt-sensing （倾斜感应）applications, as well as dynamic acceleration resulting from motion or shock. Its high resolution (3.9 mg/LSB) enables measurement of inclination（倾斜） changes less than 1.0°.
Several special sensing functions are provided. Activity and inactivity sensing detect the presence（姿态） or lack of motion by comparing the acceleration on any axis with user-set thresholds. Tap（敲击） sensing detects single and double taps in any direction. Freefall（自由落体）sensing detects if the device is falling. These functions can be mapped individually to either of two interrupt output pins. An integrated memory management system with a 32-level first in, first out (FIFO) buffer can be used to store data to minimize host processor activity and lower overall system power consumption.
Low power modes enable intelligent motion-based power management with threshold sensing and active acceleration measurement at extremely low power dissipation.
The ADXL345 is supplied in a small, thin, 3 mm × 5 mm × 1 mm, 14-lead, plastic package.
特性：
Ultralow power: as low as 23 μA in measurement mode and 0.1 μA in standby mode at VS = 2.5 V (typical)
Power consumption scales automatically with bandwidth
User-selectable resolution
Fixed 10-bit resolution
Full resolution, where resolution increases with g range, up to 13-bit resolution at ±16 g (maintaining 4 mg/LSB scale factor in all g ranges)
Embedded memory management system with FIFO technology minimizes host processor load
Single tap/double tap detection
Activity/inactivity monitoring
Free-fall detection
Supply voltage range: 2.0 V to 3.6 V
I/O voltage range: 1.7 V to VS
SPI (3- and 4-wire) and I2C digital interfaces
Flexible interrupt modes mappable to either interrupt pin
Measurement ranges selectable via serial command
Bandwidth selectable via serial command
Wide temperature range (−40°C to +85°C)
10,000 g shock survival
Pb free/RoHS compliant
Small and thin: 3 mm × 5 mm × 1 mm LGA package
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