DS726PP2
31
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
μ
s pre-emphasis equalization as a means of noise reduc-
tion. The filter response is shown in
. 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
and
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
Register Location
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
48 Hz
96 Hz
192 Hz
240 Hz
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
F1
F2
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