FXLS93421 datasheet(117/254 Pages) NXP

117 / 254 page

NXP Semiconductors

FXLS9xxxx

Dual channel inertial sensor

11.6.3 Inertial sensor ΣΔ converter

A second order sigma delta modulator converts the differential capacitance of the

transducer to a data stream that is input to the DSP. The sigma delta modulator operates

at a frequency of 1 MHz. A simplified block diagram is shown in Figure 6.

aaa-030616

CTOP

CBOT

transducer

first

integrator

α1 =

α2

β1

β2

Z-1

1 - Z-1

CINT1

second

integrator

V = 0 V, VREF

Y(Z) = {0, 1}

1-Bit

quantizer

ADC

DAC

Z-1

1 - Z-1

Figure 21. ΣΔ converter block diagram

11.6.4 Inertial sensor digital signal processor

A digital signal processor (DSP) is used to perform signal filtering and compensation. A

diagram illustrating the signal processing flow within the DSP is shown in Figure 22.

aaa-030617

INTERPOLATION

OUTPUT

SCALING

DSPOUT

SINC

FILTER

IIR

LPF

TRIM

∑ OUT

DIGITAL

CLIPPING

DOWN

SAMPLE

MOVING

AVERAGE

USER

SENSE

SCALING

DOWN

SAMPLE

OFFSET

LPF

OFFSET

MONITOR

ARMING

FUNCTION

OFFSET

CANCELLATION

RATE LIMIT

selectable output types

- F with interpolation

- F without interpolation

- M with interpolation

- M without interpolation

- F - K with interpolation

- F - K without interpolation

- M - K with interpolation

- M - K without interpolation

- F - L with interpolation

- F - L without interpolation

- M - L with interpolation

- M - L without interpolation

data type 0

yes (01)

yes (00)

yes (01)

data type 1

yes (100)

yes (001)

yes (000)

yes (100)

yes (000)

Figure 22. Signal chain diagram

Description

Sample Time

(µs)

Data

width

(Bits)

Sign

(Bits)

Over

range

(Bits)

Signal

width

(Bits)

Signal

margin

(Bits)

Typical

block

latency

Reference

A ΣΔ

2.5 µs

Section 11.6.3

B SINC Filter

16, 32, 64

22.5 µs

Section 11.6.4.1

C Trim

16, 32, 64

N/A

Section 11.6.4.2

D Digital Clipping

16, 32, 64

N/A

Section 11.6.4.3

E Low-pass filter

16, 32, 64

Filter

Dependent

Section 11.6.4.4

Table 200. Signal chain diagram legend

FXLS9xxxx

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 6 — 8 February 2021

117 / 254

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