Cirrus Logic CS42L55 - Manual (Page 25)

DS773F1 25
CS42L55
4.3 Analog In to Analog Out Passthrough
The CS42L55 accommodates analog routing of the analog input signal directly to the headphone and line
out amplifiers. This feature is useful in applications that utilize an FM tuner where audio recovered over-the-
air must be transmitted to the headphone amplifier without digital conversion in the ADC and DAC. This an-
alog passthrough path reduces power consumption and is immune to modulator switching noise that could
interfere with some tuners. This path is selected using the Line and/or HP mux bits and powering down the
ADC.
Referenced Control Register Location
PGAxVOL[5:0] .....................
ADCxATT[7:0] ......................
MAX[2:0], MIN[2:0] .............. “PGAx Volume” on page 49
“ADCx Volume” on page 50
“ALC Threshold (Address 26h)” on page 64
Referenced Control Register Location
PDN_ADCx .........................
HPxMUX..............................
LINExMUX........................... “Power Down ADC x” on page 42
“Headphone Input Select” on page 47
“Line Input Select” on page 47
Output
(after ALC)
Input (before ALC)
RRATE[5:0]
PGA Gain and/or
Attenuator
ALC
Response
MAX[2:0]
ARATE[5:0
]
below full scale
MIN[2:0]
below full scale
MIN[2:0]
below full scale
MAX[2:0]
below full scale
Figure 11. ALC Operation