Sensors

28

Freescale Semiconductor, Inc.

MMA16xxKW

3.7

Overload Response

3.7.1

Overload Performance

The device is designed to operate within a specified range. However, acceleration beyond that range (overload) impacts the

operating range output of the sensor. Acceleration beyond the range of the device can generate a DC shift at the output of the

device that is dependent upon the overload frequency and amplitude. The device g-cell is overdamped, providing the optimal

design for overload performance. However, the performance of the device during an overload condition is affected by many other

parameters, including:

• g-cell damping

• Non-linearity

• Clipping limits

• Symmetry

ified in Section 2.

Figure 21. Output Clipping Vs. Frequency

3.7.2

Sigma Delta Overrange Response

Overrange conditions exist when the signal level is beyond the full-scale range of the device but within the computational limits

of the DSP. The

ably under all cases of overrange, although the signal may include residual high frequency components for some time after re-

turning to the normal range of operation due to non-linear effects of the sensor.

5kHz

Determined by g-cell

10kHz

Acceleration (g)

Frequency (kHz)

Reg

ion

Clip

ped

by g

-ce

ll

Reg

ion

Clip

ped

by A

DC

Reg

ion

of S

igna

l Di

stor

tion

due

to

Asy

mm

etry

and

Non

-Lin

ear

ity

Region of No Signal Distortion Beyond

Specification

Region of Interest

roll-off and ADC clipping

Determined by g-cell

roll-off and full-scale range

Region Clipped

by Output