CS42L51 Datasheet, PDF (35/83 Pages) Cirrus Logic – Low Power, Stereo CODEC with Headphone Amp

4.4.5
CS42L51
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
Controls:
“Tone Control (Address 15h)” on page 63.
4.4.6
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
Volume
ATTACK/RELEASE SOUND
CUSHION
AOUTx_VOL[7:0] volume
control should NOT be
adjusted manually when
Limiter is enabled.
Output
(after Limiter)
MAX[2:0]
CUSH[2:0]
ARATE[5:0]
RRATE[5:0]
Figure 17. Peak Detect & Limiter
DS679A2
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