LC07424LP

· Digital output

-1dBFS

-5.5dBV

ADC

LIN_L

ADC_DOUT

ALC (PGA)

-1dBFS

0dB

-5.5dBV

+34dB to -14dB

Outline of operation

1. System reset/power-down

When the RESET_X pin is set to “VSS,” the system is reset, and all the circuits go into the power-down mode. After

the power is turned on, perform this operation once without fail.

When the system is reset, the contents of the register are initialized. (See register tables.)

For the subsequent startup of each function, refer to the section “Control/start/stop sequence for reducing pop noise.”

2. ALC

When the ALC is active, the PGA (programmable gain amplifier) gain value is automatically adjusted so that the

audio level becomes the preset value. The PGA gain can be adjusted in a range from +34 to -14dB.

By limiting the gain adjustment range to 0 to -14dB, this adjustment function can be made to work as a limiter

function.

The ALC operation can be stopped by a register setting. The ALC is then placed in the manual mode, and the PGA

gain is adjusted by the register setting. For details, refer to the section “Description of ALC/limiter operation.”

3. A/D converter

The A/D converter converts the analog PGA output signals into digital data, and the digital data is then output as 16-

bit serial audio data.

The A/D converter incorporates a high-pass filter for canceling DC offset.

The analog input range of the ADC is 0.6VDDadc. When VDDadc is 2.8V, 0dBfs is 1.68V.

4. D/A converter

The D/A converter converts the digital 16-bit serial audio data into analog signals.

The D/A converter incorporates a high-pass filter for canceling DC offset.

The analog input range of the ADC is 0.6VDDadc. When VDDadc is 2.8V, 0dBfs is 1.68V.

5. Selector

This selector is for selecting either the DAC or PGA output of the ALC. When the DAC output has been selected, the

DAC output signals are output as the Line/speaker amplifier output signals. When the PGA output has been selected,

the signals from line input are all turned into analog signals to become the Line/speaker amplifier output signals.

6. MIX

This is the mixing circuit for the left- and right-channel audio signals. In other words, this functions as a monaural

signal generator circuit to provide a monaural speaker amplifier input. The left- and right-channel signals are mixed

on a 1:1 basis and then output through the -2dB amplifier.

If the left- and right-channel signals are identical, the total gain becomes 4dB (= 6dB(doubled) -2dB).

No.A1619-12/32