CS4364 datasheet(25/50 Pages) CIRRUS

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DS619A1

CS4364

3.6

De-Emphasis

The CS4364 includes on-chip digital de-emphasis filters. The de-emphasis feature is included to accommo-

date older audio recordings that utilize pre-emphasis equalization as a means of noise reduction. Figure 18

shows the de-emphasis curve. The frequency response of the de-emphasis curve will scale proportionally

with changes in sample rate, Fs if the input sample rate does not match the coefficient which has been se-

lected.

In software mode the required de-emphasis filter coefficients for 32 kHz, 44.1 kHz, or 48 kHz are selected

via the de-emphasis control bits.

In hardware mode only the 44.1 kHz coefficient is available (enabled through the M2 pin). If the input sample

rate is not 44.1 kHz and de-emphasis has been selected then the corner frequencies of the de-emphasis

filter will be scaled by a factor of the actual Fs over 44,100.

3.7

ATAPI Specification

The CS4364 implements the channel mixing functions of the ATAPI CD-ROM specification. The

ATAPI functions are applied per A-B pair. Refer to Table 9 on page 41 and Figure 19 for additional informa-

tion.

Gain

-10dB

0dB

Frequency

T2 = 15 µs

T1=50 µs

3.183 kHz

10.61 kHz

Figure 18. De-Emphasis Curve

ΣΣ

A Channel

Volume

Control

Aout Ax

AoutBx

Left Channel

Audio Data

Right Channel

Audio Data

BChannel

Volume

Control

MUTE

SDINx

Figure 19. ATAPI Block Diagram (x = channel pair 1, 2, or 3)

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