DA7218 datasheet(40/154 Pages) RENESAS

40 / 154 page

Ultra-Low Power Stereo Codec

R32DS0004EE0370 Revision 3.7

Aug 9, 2024

CFR0011-120-00

Page 40

Sample rate (kHz)

11.025

22.05

44.1

88.2

100

150

101

200

110

300

111

400

9.3.1.3

Automatic Level Control

For improved sound recordings of signals with a large volume range, the DA7218 offers a fully-configurable

automatic recording level control (ALC) for microphone inputs. This is enabled via the ALC_CTRL1, and can be

enabled independently on any of the four input channels. The ALC monitors the digital signal after the ADC and

adjusts the microphones’ analog and digital gain to maintain a constant recording level, regardless of the analog

input signal level.

Operation of ALC is shown in Figure 11. When the input signal volume is high, the ALC system will reduce the

overall gain until the output volume is below the specified maximum value. When the input signal volume is low,

the ALC will increase the gain until the output volume increases above the specified minimum value. If the output

signal is within the desired signal level (between the specified minimum and maximum levels), the ALC does

nothing.

The minimum and the maximum thresholds that trigger a gain change of the ALC are programmed by the

alc_threshold_min and alc_threshold_max controls.

ALC Input

ALC Gain

ALC Output

Release time

Attack time

Figure 11. Principle of operation of the ALC

The ALC can operate in two modes; Digital-Only mode and Hybrid (combined analog and digital gain) mode.

In Digital-Only mode only the digital gain in the ADC is altered. Note that although the ALC is controlling the

gain, it does not modify any of the registers in_1l_digital_gain, in_1r_digital_gain, in_2l_digital_gain, or

DA7218 Datasheet(PDF) 40 Page - Renesas Technology Corp