ADXL330_15 Datasheet, PDF (13/16 Pages) Analog Devices – Small, Low Power, 3-Axis 3 g iMEMS Accelerometer

ADXL330
The ADXL330 output is ratiometric, therefore, the output
sensitivity (or scale factor) varies proportionally to the
supply voltage. At VS = 3.6 V, the output sensitivity is
typically 360 mV/g. At VS = 2 V, the output sensitivity is
typically 195 mV/g.
The zero g bias output is also ratiometric, so the zero g output is
nominally equal to VS/2 at all supply voltages.
The output noise is not ratiometric but is absolute in volts;
therefore, the noise density decreases as the supply voltage
increases. This is because the scale factor (mV/g) increases
while the noise voltage remains constant. At VS = 3.6 V, the
X- and Y-axis noise density is typically 230 μg/√Hz, while at
VS = 2 V, the X- and Y-axis noise density is typically 350 μg/√Hz.
Self test response in g is roughly proportional to the square of
the supply voltage. However, when ratiometricity of sensitivity
is factored in with supply voltage, the self test response in volts
is roughly proportional to the cube of the supply voltage. For
example, at VS = 3.6 V, the self test response for the ADXL330 is
approximately −275 mV for the X-axis, +275 mV for the Y-axis,
and −100 mV for the Z-axis.
X_OUT = –1g
Y_OUT = 0g
Z_OUT = 0g
At VS = 2 V, the self test response is approximately −60 mV for
the X-axis, +60 mV for the Y-axis, and −25 mV for the Z-axis.
The supply current decreases as the supply voltage decreases.
Typical current consumption at VS = 3.6 V is 375 μA, and
typical current consumption at VS = 2 V is 200 μA.
AXES OF ACCELERATION SENSITIVITY
A_Z
A_Y
TOP
A_X
Figure 31. Axes of Acceleration Sensitivity, Corresponding Output Voltage
Increases When Accelerated Along the Sensitive Axis
X_OUT = 0g
Y_OUT = 1g
Z_OUT = 0g
TOP
TOP
TOP
X_OUT = 0g
Y_OUT = –1g
Z_OUT = 0g
GRAVITY
TOP
X_OUT = 1g
Y_OUT = 0g
Z_OUT = 0g
TOP
X_OUT = 0g
Y_OUT = 0g
Z_OUT = 1g
Figure 32. Output Response vs. Orientation to Gravity
X_OUT = 0g
Y_OUT = 0g
Z_OUT = –1g
Rev. A | Page 13 of 16