AD4884BBCZ datasheet(89/116 Pages) AD

89 / 116 page

Data Sheet

AD4884

DIGITAL FEATURES

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Rev. 0 | 89 of 116

Digital Filter Conversion Pulses

The total number of CNVChX pulses required for a single filter

decimated result (sinc1 settling clocks) can be calculated using the

following formula:

SettlingCNVPulsesSINC1=2+ D+1

Note that each of the three filter types has a unique formula to

determine the number of clocks required.

For the sinc5 settling clocks, the equation is as follows:

SettlingCNVPulsesSINC5=2+ 5×D+4

For the sinc5 with compensation settling clocks, the equation is as

follows:

SettlingCNVPulsesSINC5+COMP=

2+ 35×D+10

Where D equals the decimation rate 2, 4, 8 …

Digital Filtering Settling Time

The settling time for the selected filter is the number of settling

clocks times tCONV, as follows:

Filter Settling Time=

(SettlingCNVPulsesFILTERTYPE ×tCONV

Digital Filtering Settling Time when Using FIFO

When using the FIFO with filtered data, it is important to note

that each new FIFO record of results must begin by issuing a

FILTER_SYNC signal on the first CNVChX to reset and initialize the

filter and to prevent unflushed data from being contained in the first

FIFO record result.

The minimum total number of conversion pulses required to fill a full

FIFO record can be calculated as follows:

TotalRequiredCNVs = D×WATERMARK +

Settling CNV PulsesFILTERTYPE

Where D equals the decimation rate 2, 4, 8 …

Digital Filter Response

Sinc1 Filter

Figure 136. Sinc1 Filter Response, Decimate by 2

Figure 137. Sinc1 Filter Response, Decimate by 4

Figure 138. Sinc1 Filter Response, Decimate by 8

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