CS42L52-DNZ 查看數據表（PDF） - Cirrus Logic

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CS42L52-DNZ

Low-power, Stereo CODEC w/ Headphone & Speaker Amps

Cirrus Logic 

Input

M AX[2:0]

5/13/08

CS42L52

Lim iter

Volum e

A TTAC K/RELEA SE SO U N D

CU SHIO N

O utput

(after Lim iter)

M AX[2:0]

CU SH[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 Passthrough

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

passthrough 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 details

on how this ADC power-down override functions in accordance with the state of the speaker channels.

The shaded cells represent normal ADC operation when passthrough 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

DS680F1

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