CS5471 datasheet(8/14 Pages) CIRRUS

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CS5471

centage of full scale. Table 1 below illustrates the

ideal relationship between the differential voltage

presented any one of the input channels and the

corresponding output code. Note that for the cur-

rent channels, the state of the GAIN input pin is as-

sumed to driven low, such that the PGA gain on the

current channels is 1x. If the PGA gain of the cur-

rent channels is set to 20x, then a +40 mV differen-

tial voltage presented across the “IIN+” and “IIN-”

pins will cause a (nominal) output code of 32767.

Table 1. Nominal Relationship for Differential Input

Voltage vs. Output Code, for all channels. (Assume PGA

gain is set to 1x.)

2.3

High Rate Digital Filters

If the OWRS pin is set to logic low, the high-rate

filters are implemented as fixed sinc3 filters with

the following transfer function:

This filter samples the modulator bit stream at

XIN/8 Hz and decimates to XIN/2048 Hz.

If the OWRS pin is set to logic high, then the trans-

fer function is

The above filter samples the modulator bit stream

at XIN/8 Hz and decimates to XIN/1024 Hz.

2.4

Serial Interface

The CS5471 communicates with a target device via

a master serial data output port. Output data is pro-

vided on the SDO output synchronous with the

SCLK output.

A third output, FSO, is a framing signal used to sig-

nal the start of output data. These three outputs will

be driven as long as the SE (serial enable) input is

held high. Otherwise, these outputs will be high im-

pedance.

Input Voltage

(mV0-pk)

Output Code

(hexadecimal)

Output Code

(decimal)

+800

7FFF

32767

0.0122 to 0.0366

0001

-0.0122 to 0.0122

0000

-0.0122 to -0.0366

FFFF

-1

-800

8000

-32768

()

256

–

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







()

128

–

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







SCLK

FSO

SDO

Channel 1 (V)

64 0-value bits

Channel 1 (I)

Each data segment

is 16 bits long.

Figure 3. Serial Port Data Transfer

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