DS726PP2
61
CS4525
6.5
Analog Inputs
Very few components are required to interface between the audio source and the CS4525’s analog inputs,
AINL and AINR. A single order passive low-pass filter is recommended to prevent high-frequency content
from aliasing into the audio band due to the analog-to-digital conversion process. Also, a DC-blocking ca-
pacitor is required as the CS4525’s analog inputs are internally biased to VQ.
The recommended analog input circuit is shown in
below will accommodate full-scale input volt-
ages as defined in the
table on
. This circuit provides the necessary
high-frequency filtering with a first-order passive low-pass filter that has less than 0.05 dB of attenuation at
24 kHz. It also includes a DC blocking capacitor to accommodate the analog input pins’ bias level.
To interface 2 V
RMS
input signals with the CS4525’s analog inputs, an external resistor divider is required.
shows the recommended input circuit for 2 V
RMS
inputs. It includes a -8.4 dB passive attenuator
to condition the input signal for the CS4525’s full-scale input voltage, a first-order passive low-pass filter that
has less than 0.05 dB of attenuation at 24 kHz, and a DC blocking capacitor to accommodate for the analog
input pins’ bias level. The passive attenuator network should be placed as close as possible to the CS4525’s
analog input pins to reduce the potential for noise and signal coupling into the analog input traces.
It should be noted that the external DC blocking capacitor forms a high-pass filter with the CS4525’s input
impedance. Both filters shown above have less than 0.2 dB attenuation at 20 Hz due to this effect. Increas-
ing the value of this capacitor will lower this high-pass corner frequency, and decreasing it’s value will in-
crease the corner frequency.
CS4525
AINL
AINR
1 µF
365
Ω
1800 pF
Left Input
1 µF
365
Ω
1800 pF
Right Input
100 k
Ω
100 k
Ω
C0G
C0G
Figure 28. Recommended Unity Gain Input Filter
CS4525
AINL
100 pF
Left Input
C0G
1 µF
5.62 k
Ω
8.06 k
Ω
AINR
100 pF
Right Input
C0G
1 µF
5.62 k
Ω
8.06 k
Ω
Figure 29. Recommended 2 V
RMS
Input Filter