CS4525 datasheet(31/98 Pages) CIRRUS

31 / 98 page

DS726PP1

CS4525

6.1.4.4

De-Emphasis

The CS4525 includes an on-chip digital de-emphasis filter optimized for a sample rate of 44.1 kHz to ac-

commodate audio recordings that utilize 50/15

μs pre-emphasis equalization as a means of noise reduc-

tion. The filter response is shown in Figure 15. The de-emphasis filter is enabled and disabled by the

DeEmph bit in the Tone Config register.

6.1.4.5

Tone Control

The CS4525 implements configurable bass and treble shelving filters to easily accommodate system tone

control requirements. Each shelving filter has 4 selectable corner frequencies, and provides a cut/boost

range from -10.5 dB to +12.0 dB in 1.5 dB increments. The tone control is enabled by the EnToneCtrl bit

in the Tone Config register.

Each tone control is implemented with one of two preset internal filter sets. One set is optimized for a

32 kHz sample rate, and the other is optimized for 44.1 kHz, 48 kHz, and 96 kHz sample rates. The

CS4525 automatically detects the input sample rate and chooses the appropriate filter set to apply. The

available corner frequencies are shown in tables 2 and 3 below and are configured with the BassFc[1:0]

and TrebFc[1:0] bits in the Tone Config register.

Note that the corner frequency of each filter set scales linearly with the input sample rate.

When the internal ADC is used as the serial audio data source, the input sample rate is nominally 48 kHz

and the corresponding shelving frequency corners are available.

Referenced Control

DeEmph .............................. “De-Emphasis Control (DeEmph)” on page 76

Input Sample Rate

Bass Fc 0

Bass Fc 1

Bass Fc 2

Bass Fc 3

32 kHz

50 Hz

100 Hz

200 Hz

250 Hz

44.1 kHz

48Hz

96Hz

192 Hz

240Hz

48 kHz, 96 kHz

52 Hz

104 Hz

208 Hz

260 Hz

Table 2. Bass Shelving Filter Corner Frequencies

T2 = 15 µs

T1=50 µs

0.07218 Fs

0 dB

-10 dB

0.24059 Fs

32 kHz, 44.1 kHz, 48 kHz

96 kHz

0.03609 Fs

0.12030 Fs

Normalized to Fs

Frequency (Hz)

Gain (dB)

Nominal Sample Rate

Figure 15. De-Emphasis Filter

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