AFE5804 datasheet(33/82 Pages) TI2

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ADS5294

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SLAS776E – NOVEMBER 2011 – REVISED APRIL 2018

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Feature Description (continued)

(1)

EN_CUSTOM_FILT is the D15 of register 5A (Hex) to B9 (Hex).

9.3.4 Decimation Filter

ADS5294 includes an option to decimate the ADC output data using filters. Once the decimation is enabled, the

decimation rate, frequency band of the filter can be programmed. In addition, the user can select either the pre-

defined or custom coefficients.

Table 1. Digital Filters(1)

DECIMATION

TYPE OF FILTER

DATA

_RATE

FILTERn

_RATE

FILTERn

_COEFF_SET

ODD_TAP

USE

_FILTER

_CHn

EN_CUSTOM

_FILT

Decimate by 2

Built-in low-pass odd-tap filter (pass band = 0 to

fS / 4)

000

Built-in high-pass odd-tap filter (pass band = fS /

4 to fS /2)

000

001

Decimate by 4

Built-in low-pass even-tap filter (pass band = 0

to fS / 8)

001

010

Built-in first band pass even tap filter (pass band

= fS / 8 to fS / 4)

001

011

Built-in second band pass even tap filter (pass

band = fS / 4 to 3 fS / 8)

001

100

Built-in high pass odd tap filter (pass band = 3

fS / 8 to fS / 2)

001

101

Decimate by 2

Custom filter (user-programmable coefficients)

000

0 and 1

Decimate by 4

Custom filter (user-programmable coefficients)

001

000

0 and 1

Decimate by 8

Custom filter (user-programmable coefficients)

100

000

0 and 1

Bypass

decimation

Custom filter (user-programmable coefficients)

011

000

0 and 1

9.3.5 Decimation Filter Equation

In the default setting, the decimation filter is implemented as a 24-tap FIR filter with symmetrical coefficients

(each coefficient is 12-bit signed). By setting the register bit ODD_TAPn = 1, a 23-tap FIR is implemented

9.3.5.1 Pre-defined Coefficients

The built-in filters (lowpass, highpass, and bandpass) use pre-defined coefficients. The frequency responses of

the build-in decimation filters with different decimation factors are shown in Figure 48.

AFE5804 Datasheet(PDF) 33 Page - Texas Instruments

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