CS4270_06 Datasheet, PDF (27/49 Pages) Cirrus Logic – 24-Bit, 192 kHz Stereo Audio CODEC

CS4270
5.2.8 De-Emphasis
One de-emphasis mode is available via the Control Port and is optimized for 44.1 kHz sampling rate.
5.2.9 Oversampling Modes
The CS4270 operates in one of three oversampling modes based on the input sample rate. Mode selec-
tion is determined by the FM_&_M/S_Mode[1:0] bits in the Functional Mode register (03h). Single-Speed
Mode supports input sample rates up to 54 kHz and uses a 128x oversampling ratio. Double-Speed Mode
supports input sample rates up to 108 kHz and uses an oversampling ratio of 64x. Quad-Speed Mode
supports input sample rates up to 216 kHz and uses an oversampling ratio of 32x. See Table 10 for Con-
trol Port Mode settings.
5.3 De-Emphasis Filter
The CS4270 includes on-chip digital de-emphasis. Figure 14 shows the de-emphasis curve for Fs equal
to 44.1 kHz. The frequency response of the de-emphasis curve will scale proportionally with changes in
sample rate, Fs. Please see Section 5.1.7 for the desired de-emphasis control for Stand-Alone Mode and
Section 5.2.8 for Control Port Mode.
The de-emphasis feature is included to accommodate audio recordings that utilize 50/15 µs pre-emphasis
equalization as a means of noise reduction.
De-emphasis is only available in Single-Speed Mode.
Gain
dB
0dB
T1=50 µs
-10dB
T2 = 15 µs
F1
3.183 kHz
F2 Frequency
10.61 kHz
Figure 14. De-Emphasis Curve
DS686PP1
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