Click-and-pop reduction – Rainbow Electronics MAX98088 User Manual

Page 108

Stereo Audio Codec

with FLEXSOUND Technology

MAX98088

108

Click-and-Pop Reduction

The IC includes extensive click-and-pop reduction cir-
cuitry. The circuitry minimizes clicks and pops at turn-on,
turn-off, and during volume changes.
Zero-crossing detection is implemented on all analog
PGAs and volume controls to prevent large glitches
when volume changes are made. Instead of making a
volume change immediately, the change is made when
the audio signal crosses the midpoint. If no zero-crossing
occurs within the timeout window, the change is forced.
Volume slewing breaks up large volume changes into the
smallest available step size and the steps through each
step between the initial and final volume setting. When

enabled, volume slewing also occurs at device turn-on
and turn-off. During turn-on the volume is set to mute
before the output is enabled. Once the output is on, the
volume ramps to the desired level. At turn-off the volume
is ramped to mute before the outputs are disabled.
When there is no audio signal zero-crossing detection
can prevent volume slewing from occurring. Enable
enhanced volume slewing to prevent the volume control-
ler from requesting another volume level until the previ-
ous one has been set. Each step in the volume ramp
then occurs after a zero crossing has occurred in the
audio signal or the timeout window has expired. During
turn-off, enhance volume slewing is always disabled.

Table 30. Click-and-Pop Reduction Register

BIT

NAME

DESCRIPTION

0x47

VS2EN

Enhanced Volume Smoothing
During volume slewing, the controller waits for each step in the ramp to be applied
before sending the next step. When zero-crossing detection is enabled this prevents
large steps in the output volume when no zero crossings are detected.
0 = Enabled
1 = Disabled
Applies to volume changes in HPVOLL, HPVOLR, RECVOL, SPVOLL, and SPVOLR.

VSEN

Volume Adjustment Smoothing
Volume changes are smoothed by stepping through intermediate steps. Also ramps
the volume from minimum to the programmed value at turn-on and back to minimum at
turn-off.
0 = Enabled
1 = Disabled
Applies to volume changes in HPVOLL, HPVOLR, RECVOL, SPVOLL, and SPVOLR.

ZDEN

Zero-Crossing Detection
Holds volume changes until there is a zero crossing in the audio signal. This reduces
click and pop during volume changes (zipper noise). If no zero crossing is detected
within 100ms, the volume change is forced.
0 = Enabled
1 = Disabled
Applies to volume changes in PGAM1, PGAM2, PGAOUTA, PGAOUTB, PGAOUTC,
HPVOLL, HPVOLR, RECVOL, SPVOLL, and SPVOLR.

EQ2EN

See the 5-Band Parametric EQ section.

EQ1EN