AD4134 datasheet(39/92 Pages) AD

39 / 92 page

Data Sheet

AD4134

CIRCUIT INFORMATION

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Rev. 0 | 39 of 92

The interpolation factor depends on the ODR selected. The frac-

tional sample rate conversion of the ASRC allows the final ODR to

be asynchronous to the sampling clock of the modulator.

The output of the ASRC is then decimated by an integer in the

digital filter to produce the final ODR.

The ASRC only response depends on the ODR selected and has

a notch at the value of interpolation factor × ODR frequency. The

interpolation factor values for the various ODRs are shown in Table

18.

Table 18. Interpolation Factor Values for Different ODR Ranges

ODR Range

Interpolation Factor Value

750 kSPS to 1.496 MSPS

375 kSPS to 749.999 kSPS

366.99 SPS to 374.999 kSPS

10 SPS to 366.99 SPS

1024

For example, the ASRC response for an ODR of 374 kSPS shows

a notch at 32 × 374 kHz = 11.968 MHz, as shown in Figure 72.

Figure 72. ASRC Only Response for ODR = 374 kSPS

Similarly, the ASRC response for an ODR of 1496 kSPS shows a

notch at 8 × 1496 kHz = 11.968 MHz, as shown in Figure 73.

Figure 73. Response for ODR of 1496 kSPS

The available output data rate range varies based on the digital

filter type and the ASRC mode selected (see the Digital Filters

section for more information).

The ASRC on the AD4134 has the following two modes of opera-

tion:

►

In master mode, the ODR pin is output and the ODR is set

through the pin configuration or a register write.

►

In slave mode, the ODR pin is input to the AD4134 and the ODR

is set with an external clock source.

ASRC Master Mode

In master mode, the ASRC resamples the interpolated modulator

output at a fixed ratio to the modulator clock (see Figure 74). The

ratio is internally calculated based on the user setting of the final

ODR. The user can configure the ODR through configuration of the

ODR pin in pin control mode or through register configuration in SPI

control mode.

In ASRC master mode, the ODR pin behaves as an output. It

produces a pulse train signal in the frequency of the output data

rate. The ADC output data is made available for sampling with

respect to the ODR signal. For details of the ASRC master mode

output data rate setting, see the ASRC Master Mode section.

Figure 74. ASRC Master Mode Functional Diagram

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