CS42L51
4.4.5
4.4.6
Tone Control
Shelving filters are used to implement bass and treble (boost and cut) with four selectable corner frequen-
cies. Boosting will affect peak detect and limiting when levels exceed the maximum threshold settings.
Software
“Tone Control (Address 15h)” on page 63.
Controls:
Limiter
When enabled, the limiter monitors the digital input signal before the DAC modulator, detects when levels
exceed the maximum threshold settings and lowers the AOUT volume at a programmable attack rate be-
low the maximum threshold. When the input signal level falls below the maximum threshold, the AOUT
volume returns to its original level set in the Volume Control register at a programmable release rate. At-
tack and release rates are affected by the DAC soft ramp/zero cross settings and sample rate, Fs. Limiter
soft ramp and zero cross dependency may be independently enabled/disabled.
Recommended settings: Best limiting performance may be realized with the fastest attack and slowest
release setting with soft ramp enabled in the control registers. The “cushion” bits allow the user to set a
threshold slightly below the maximum threshold for hysteresis control - this cushions the sound as the lim-
iter attacks and releases. NOTE: When the Limiter is enabled the AOUT Volume is automatically con-
trolled and should not be adjusted manually. Alternative volume control may be realized using the
PCMMIXx_VOL[6:0] bits.
Software
Controls:
“Limiter Release Rate Register (Address 1Ah)” on page 66, “Limiter Attack Rate Register (Address
1Bh)” on page 67, “DAC Control (Address 09h)” on page 55
Input
MAX[2:0]
Limiter
AOUTx_VOL[7:0] volume
ATTACK/RELEASE SOUND
CUSHION
control should NOT be
Volume
adjusted manually when
Limiter is enabled.
Output
(after Limiter)
CUSH[2:0]
MAX[2:0]
ARATE[5:0]
RRATE[5:0]
Figure 17. Peak Detect & Limiter
DS679A2
35
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