Data Sheet

ADXL314

THEORY OF OPERATION

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Rev. A | 13 of 27

Table 11. Interrupt Pin Digital Output

Parameter

Test Conditions

Limit1

Unit

Min

Max

Rise Time and Fall Time

Rise Time (tR)2

Load capacitance (CLOAD) =

150 pF

210

ns

Fall Time (tF)3

CLOAD = 150 pF

150

ns

1 Limits based on characterization results, not production tested.

2 The rise time is measured as the transition time from VOL, max to VOH, min of the interrupt pin.

3 The fall time is measured as the transition time from VOH, min to VOL, max of the interrupt pin.

SELF TEST

The ADXL314 incorporates a self test feature that effectively

tests its mechanical and electronic systems simultaneously. When

the self test function is enabled (via the SELF_TEST bit in the

DATA_FORMAT register, Address 0x31), an electrostatic force is

exerted on the mechanical sensor.

This electrostatic force moves the mechanical sensing element in

the same manner as acceleration, and it is additive to the external

acceleration experienced by the device. This added electrostatic

force results in an output change in the x-axis, y-axis, and z-axis.

Because the electrostatic force is proportional to VS2, the output

change varies with VS.

The self test response exhibits bimodal behavior in all axes. How-

ever, the z-axis self test change can be used to effectively perform

a self test check. For the self test function to operate correctly, the

device must be in normal power operation (LOW_POWER bit = 0 in

the BW_RATE register, Address 0x2C) and be configured for a data

rate from 100 Hz to 800 Hz, or for a data rate of 3200 Hz.

The self test response cannot be used as a reliable indicator of

potential shift in device sensitivity.

For more information about the self test feature, see the Using Self

Test section.