f − Frequency − kHz

−140

−120

−100

−80

−60

−40

−20

0

0

5

10

15

20

Input Level = −0.5 dB

Data Points = 8192

G015

c

f

RC

1

2

=

p

23

PCM1802

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Typical Application (continued)

8.2.1 Design Requirements

For this design example, use the parameters listed in Table 10 as the input parameters.

Table 10. Design Parameters

PARAMETER

VALUE

Analog input voltage

0 VP–P to 3 VP–P

Output

PCM audio data

System clock input frequency

2.048 MHz to 49.152 MHz

Output sampling frequency

8 kHz to 96 kHz

Power supply

3.3 V and 5 V

8.2.2 Detailed Design Procedure

8.2.2.1 Control Pins

The FMT, MODE, OSR, and BYPASS control pins are controlled by tying up to VDD, down to GND, or driven

with GPIO from the DSP or audio processor.

8.2.2.2 DSP or Audio Processor

In this application a DSP or audio processor acts as the audio master, and the PCM1802 acts as the audio

slave. This means the DSP or audio processor must be able to output audio clocks that the PCM1802 can use to

process audio signals.

8.2.2.3 Input Filters

For the analog input circuit an AC-coupling capacitor must be placed in series with the input. This removes the

DC component of the input signal. An RC filter can also be implemented to filter out of band noise to reduce

aliasing. Equation 1 calculates the cutoff frequency of the optional RC filter for the input.

(1)

8.2.3 Application Curve

Figure 29. Amplitude vs Frequency