ADXL335 Datasheet

ADXL335
Rev. A | Page 12 of 16
USE WITH OPERATING VOLTAGES OTHER THAN 3 V
The ADXL335 is tested and specified at V
S
= 3 V; however, it
can be powered with V
S
as low as 1.8 V or as high as 3.6 V. Note
that some performance parameters change as the supply voltage
is varied.
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