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ADXL343 Datasheet(Arkusz danych) 11 Page - Analog Devices
AD [Analog Devices]
Preliminary Technical Data
Rev. PrA | Page 11 of 36
THEORY OF OPERATION
The ADXL343 is a complete 3-axis acceleration measurement
system with a selectable measurement range of ±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, that
allows the device 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 forces due to applied acceleration.
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 proof mass and unbalances
the differential capacitor, resulting in a sensor output whose ampli-
tude is proportional to acceleration. Phase-sensitive demodulation
is used to determine the magnitude and polarity of the acceleration.
Power can be applied to V
in any sequence without
damaging the ADXL343. All possible power-on modes are
summarized in Table 6. The interface voltage level is set with
the interface supply voltage, V
, which must be present to
ensure that the ADXL343 does not create a conflict on the
communication bus. For single-supply operation, V
the same as the main supply, V
. In a dual-supply application,
can differ from V
to accommodate the desired
interface voltage, as long as V
is greater than or equal to V
is applied, the device enters standby mode, where power
consumption is minimized and the device waits for V
applied and for the command to enter measurement mode to be
received. (This command can be initiated by setting the measure
bit (Bit D3) in the POWER_CTL register (Address 0x2D).) In
addition, while the device is in standby mode, any register can be
written to or read from to configure the part. It is recommended
to configure the device in standby mode and then to enable
measurement mode. Clearing the measure bit returns the
device to the standby mode.
Table 6. Power Sequencing
The device is completely off, but there is a potential for a communication bus conflict.
The device is on in standby mode, but communication is unavailable and creates a conflict on
the communication bus. The duration of this state should be minimized during power-up to
prevent a conflict.
No functions are available, but the device does not create a conflict on the communication bus.
Standby or Measurement
At power-up, the device is in standby mode, awaiting a command to enter measurement
mode, and all sensor functions are off. After the device is instructed to enter measurement
mode, all sensor functions are available.
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