User Manual

ADXL335
Rev. 0 | Page 12 of 16
The ADXL335 output is ratiometric, therefore, the output
sensitivity (or scale factor) varies proportionally to the
supply voltage. At V
S
= 3.6 V, the output sensitivity is typi-
cally 360 mV/g. At V
S
= 2 V, the output sensitivity is typically
195 mV/g.
The zero g bias output is also ratiometric, thus the zero g
output is nominally equal to V
S
/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 V
S
= 3.6 V,
the X-axis and Y-axis noise density is typically 120 µg/√Hz,
whereas at V
S
= 2 V, the X-axis and Y-axis noise density is
typically 270 g/√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 V
S
= 3.6 V, the self-test response for the ADXL335
is approximately −560 mV for the X-axis, +560 mV for the
Y-axis, and +950 mV for the Z-axis.
At V
S
= 2 V, the self-test response is approximately −96 mV for
the X-axis, +96 mV for the Y-axis, and −163 mV for the Z-axis.
The supply current decreases as the supply voltage decreases.
Typical current consumption at V
S
= 3.6 V is 375 µA, and typi-
cal current consumption at V
S
= 2 V is 200 µA.
AXES OF ACCELERATION SENSITIVITY
A
Z
A
Y
A
X
07808-025
Figure 23. Axes of Acceleration Sensitivity; Corresponding Output Voltage
Increases When Accelerated Along the Sensitive Axis.
X
OUT
= –1g
Y
OUT
= 0g
Z
OUT
= 0g
GRAVITY
X
OUT
= 0g
Y
OUT
= 1g
Z
OUT
= 0g
X
OUT
= 0g
Y
OUT
= –1g
Z
OUT
= 0g
X
OUT
= 1g
Y
OUT
= 0g
Z
OUT
= 0g
X
OUT
= 0g
Y
OUT
= 0g
Z
OUT
= 1g
X
OUT
= 0g
Y
OUT
= 0g
Z
OUT
= –1g
TOP
TOP
TOP
TOP
07808-026
Figure 24. Output Response vs. Orientation to Gravity