ADXL330 datasheet(13/16 Pages) AD

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ADXL330

Rev. 0 | Page 13 of 16

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.

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

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Figure 31. Axes of Acceleration Sensitivity, Corresponding Output Voltage

Increases When Accelerated Along the Sensitive Axis

XOUT = –1g

YOUT = 0g

ZOUT = 0g

GRAVITY

XOUT = 0g

YOUT = 1g

ZOUT = 0g

XOUT = 0g

YOUT = –1g

ZOUT = 0g

XOUT = 1g

YOUT = 0g

ZOUT = 0g

XOUT = 0g

YOUT = 0g

ZOUT = 1g

XOUT = 0g

YOUT = 0g

ZOUT = –1g

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Figure 32. Output Response vs. Orientation to Gravity

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