AD4134 datasheet(41/92 Pages) AD

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Data Sheet

AD4134

CIRCUIT INFORMATION

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Rev. 0 | 41 of 92

DIGITAL FILTERS

The AD4134 offers four types of digital filters: sinc3, sinc6, and two

wideband filters. The sinc3 filter type includes an additional setting

with 50 Hz/60 Hz rejection (see Table 19). In SPI control mode,

these filters can be chosen on a per channel basis. In pin control

mode, only one filter can be selected for all channels.

The digital filters available can be operated at any output data rate

within the range mentioned in Table 19, allowing the user to choose

the optimal input bandwidth and speed of the conversion vs. the

desired power mode or resolution.

Table 19. Digital Filter Options

Filter Name

−3 dB Band-

width (Hz)

ODR

Range

Description

Sinc3 Filter

0.2617 × OD

0.01

kSPS to

1496 kS

Fast settling

Sinc3 Filter with 50

Hz/60 Hz Rejection

0.2753 ×

ODR

0.01

kSPS to

1496 kS

Fast settling with simulta-

neous 50 Hz and 60 Hz

rejection when ODR = 50

SPS

Sinc6 Filter

0.1861 ×

ODR

2.5

kSPS to

1.496 M

SPS

Balancing settling with re-

jection

Wideband 0.433 × ODR

Filter

0.433 × ODR 2.5

kSPS to

374 kSP

Wideband low ripple filter

Wideband 0.10825 ×

ODR Filter (Available

Only in SPI Control

Mode)

0.108 × ODR 2.5

kSPS to

374 kSP

Wideband low ripple filter

with lower bandwidth

Sinc Filters

The sinc filters on the AD4134 employ a cascaded integrator comb

(CIC) topology to produce a response similar to a sinc function,

equivalent to a running averaging operation on the output samples

from the ASRC. The sinc filters enable a low latency signal path,

useful for applications such as time domain analysis, measurement

of dc inputs, and for control loops. Two types of sinc filters are

available on the AD4134. The sinc6 filter offers a balance between

noise rejection and latency, whereas the sinc3 filter offers the

minimum latency path and supports a wide ODR range down to 10

SPS.

The sinc6 filter has a −3 dB bandwidth of 0.1861 × ODR, and

the sinc3 filter has a −3 dB bandwidth of 0.2617 × ODR. The

Noise Performance and Resolution section contains the noise per-

formance for the sinc filters across power modes and ODR values.

Figure 76. Sinc6 Filter Frequency Response

Figure 77. Sinc3 Filter Frequency Response

The settling of the sinc6 filter is 6.5/ODR. For a 374 kSPS ODR, the

time to fully settled data is 17.37 µs.

Figure 78. Sinc6 Filter Step Response

The settling of the sinc3 filter is 3.5/ODR cycles. Therefore, for a

374 kSPS ODR, the time to fully settled data is 9.35 µs.

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