MMA81XXTKEG

Sensors

Freescale Semiconductor

9

SECTION 2 SUPPORT MODULES

2.1

MASTER OSCILLATOR

A temperature-compensated internal oscillator provides a stable timing reference for the device. The oscillator is factory-trimmed

to operate at a nominal frequency of 4 MHz.

2.2

VOLTAGE REGULATION

The internal voltage regulator has minimum voltage level detection, which will hold the device in reset and prevent data

transmission should the regulator output fall during operation. The regulator also has an input voltage clamp to limit the power

2.3

BESSEL FILTER

180-Hz, 2-pole and 400 Hz 4-pole Bessel filter options are provided. The low-pass filter is implemented within a two stage

switched capacitor amplifier. The overall gain of the Bessel filter is set to a fixed value. The output of the Bessel filter output acts

2.4

STATUS MONITORING

A number of abnormal conditions are detected by MMA81XXTKEG/MMA82XXTKEG and the behavior of the device altered if a

fault is detected. Detected fault conditions and consequent device behavior is summarized in the table below. Certain conditions,

e.g. ground loss, are qualified by device configuration. Figure 2-1 provides a representation of fault conditions, applicable quali-

fiers and effects.

Table 2-1 Fault Condition Response Summary

Condition

Description

Device Behavior

Internally regulated voltage below operating

level

Device continuously undergoes reset, bus switch

open, no response to DSI commands

than 1 ms

Frame Timeout

Bus voltage remains below frame threshold

than 1 ms

Undervoltage (U) flag set, short-word Read

Acceleration Data response value equals zero

Fuse Fault

OTP fuse threshold failure

Accelerometer Status (S) flag set, short-word Read

Acceleration Data response value equals zero

Parity Fault

Parity failure detected in factory or customer

programmed OTP data

Ground Fault

Ground loss detected for more than 4.096 ms

Accelerometer Status (S) and Ground Fault (GF) flags

set, short-word Read Acceleration Data response

value equals zero