Cirrus Logic CS4228A - Manual (Page 28)

CS4228A
28
AINR+, AINR-,
AINL+, AINL- 16, 17, 19, 20 Differential Analog Inputs (Input) - The analog signal inputs are presented differentially to
the modulators via the AINR+/- and AINL+/- pins. The + and - input signals are 180° out of
phase resulting in a nominal differential input voltage of twice the input pin voltage. These
pins are biased to the internal reference voltage. A passive anti-aliasing filter is required for
best performance, as shown in Figure 6. The inputs can be driven at -1 dB FS single-ended
if the unused input is connected to ground through a large value capacitor. A single ended
to differential converter circuit can also be used for slightly better performance.
FILT 18 Internal Voltage Filter (Output) - Filter for internal circuits. An external capacitor is required
from FILT to analog ground, as shown in Figure 6. FILT is not intended to supply external
current. FILT+ has a typical source impedance of 250 k
Ω and any current drawn from this
pin will alter device performance. Care should be taken during board layout to keep dynamic
signal traces away from this pin.
VA 21 Analog Power (Input) - Power for the analog and reference circuits.
AGND 22 Analog Ground (Input) - Analog ground reference.
FR, FL, SR, SL
SUB, CENTER 23, 24, 25,
26, 27, 28
Analog Outputs (Output) - Analog outputs from the DACs. The full scale analog output level
is specified in the Analog Characteristics specifications table. The amplitude of the outputs
is controlled by the Digital Volume Control registers 0x07 - 0x0C.