MMA6525KW datasheet(35/56 Pages) FREESCALE

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Sensor

Freescale Semiconductor, Inc.

MMA65xx

3.8.6

Signal Compensation

The device includes internal OTP and signal processing to compensate for sensitivity error and offset error. This compensation

is necessary to achieve the specified parameters in Section 2.4.

3.8.7

Output Scaling

The 20 bit digital output from the DSP is clipped and scaled to a 12-bit data word which spans the acceleration range of the

device. Figure 22 shows the method used to establish the output acceleration data word from the DSP output.

Figure 22. 12-Bit Output Scaling Diagram

3.8.8

Data Interpolation

The device includes 2 to 1 data interpolation to minimize the system sample jitter. Each result produced by the digital signal

processing chain is delayed one half of a sample time, and the interpolated value of successive samples is provided between

sample times. This operation is illustrated below.

Figure 23. Data Interpolation Timing

Over Range

Signal

Noise

D19 D18 D17 D16 D15 D14 D13 D12 D11 D10

12-Bit Data Word

D15 D14 D13 D12 D11 D10

Using Rounding

Sn-3

Sn-2

Internal Sample Rate

Output Sample Rate

Sn-1

Sn-2

–

-------------------------------

–

-------------------------------

–

------------------------

Sn-3

SPI acceleration request occurring in this window receives interpolated sample

SPI acceleration request occurring in this window receives true sample.

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