WM8523GEDT WOLFSON [Wolfson Microelectronics plc], WM8523GEDT Datasheet - Page 30

• Manufacturer Part Number: WM8523GEDT
• Description: 24-bit 192kHz Stereo DAC with 2Vrms Ground Referenced Line Output
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

WM8523
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Ramp Volume Changes
If ramp volume changes are selected, the ramp rate is dependent upon the sampling rate. The ramp
rates for common audio sample rates are shown in Table 15.
Table 15 Volume Ramp Rate
For example, when using a sample rate of 48kHz, the time taken for a volume change from an initial
setting of 0dB to -20dB is calculated as follows:
Zero cross is not used when ramping. The volume level in the DAC is set by the user in 0.25dB
increments, but during the volume ramp increments of 0.125dB are actually used. This step size is
inaudible and means there is no requirement to wait until a zero crossing occurs. Another benefit of not
using zero cross when ramping is that predictable ramp times are produced – there is no signal
dependency on the ramp time.
Step Volume Changes and Zero Cross
The step volume control includes optional zero cross functionality. When zero cross is enabled, by
setting DAC_ZCEN=1, volume changes are not applied until the signal crosses zero so no discontinuity
is seen in the output signal. Zero cross helps to prevent pop and click noise when changing volume
settings and is therefore recommended if using step volume changes.
The zero cross function includes a timeout which forces volume changes if a zero cross event does not
occur. The timeout period is 14400 samples, equivalent to 300ms at 48kHz sample rate.
Table 16 Zero Cross Control
Table 17 gives a summary of the volume mode settings and their effect.
Table 17 Volume Change Summary
SAMPLE RATE FOR DAC (kHz)
DAC_CTRL3
DAC_VOL_
REGISTER
ADDRESS
UP_RAMP
05h
R5
0
0
1
1
0
0
1
1
Volume Change (dB) x Volume Ramp Rate (ms/dB) = 20 x 0.17 = 3.4ms
176.4
44.1
88.2
192
32
48
96
8
DOWN_RAMP
BIT
4
DAC_VOL_
0
1
0
1
0
1
0
1
LABEL
DAC_
ZCEN
DAC_ZCEN
GAIN RAMP RATE
DEFAULT
0
0
0
0
1
1
1
1
(ms/dB)
0
0.25
0.18
0.17
0.08
0.05
0.04
0.1
1
Zero Cross Enable
0 = Do not use zero cross
1 = Use zero cross
Step, use zero cross
Step, use zero cross
VOLUME CHANGE
Step, no zero cross
Step, no zero cross
Ramp
Ramp
Ramp
Ramp
UP
DESCRIPTION
PD, Rev 4.1, August 2011
Step, use zero cross
Step, use zero cross
VOLUME CHANGE
Step, no zero cross
Step, no zero cross
Production Data
DOWN
Ramp
Ramp
Ramp
Ramp
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