CS42L52 Datasheet, PDF (32/82 Pages) Cirrus Logic – Low Power, Stereo CODEC w/Headphone & Speaker Amps

In p u t
M AX[2:0]
CS42L52
Lim iter
V olum e
A TTA C K /R ELEA SE S O U N D
C U SH IO N
O utput
(after Lim iter)
M AX[2:0]
C U S H [2 :0 ]
A R A T E [5 :0 ]
R R A T E [5 :0]
Figure 14. Peak Detect & Limiter
4.4 Analog In to Analog Out Passthru
The CS42L52 accommodates analog routing of the analog input signal directly to the headphone 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 analog passthru
path reduces power consumption and is immune to modulator switching noise that could interfere with some
tuners.
4.4.1
Overriding the ADC Power Down
To accommodate automatic activation of the speaker amplifier when the SPK/HP_SW switch pin chang-
es, the CS42L52 provides the option to automatically power up the ADC whenever the analog signal must
route to the digital PWM modulator, regardless of the PDN_ADC bit. Refer to the table below for how this
ADC power-down override functions in accord with the state of the speaker channels. The shaded cells
represent normal ADC operation when passthru is disabled.
PDN_ADC
0
1
PASSTHRU
x
0
1
PDN_OVRD
x
x
0
1
Speaker Channel
x
x
x
OFF
ON
ADC Status
Powered UP
Powered DOWN
Powered DOWN
Powered DOWN
Powered UP
When PASSTHRU and PDN_OVRD are enabled, turning the speaker channel ON (by writing ‘11’b to
SPKx_PDN[1:0] or by automatic activation of the headphone detect switch, SPK/HP_SW) will automati-
cally disable the ADCx_PDN in order to convert the analog input to a digital signal for the PWM modulator.
This allows automatic analog input routing to the speaker amplifiers.
32
DS680A1