xwm8722eds ETC-unknow, xwm8722eds Datasheet - Page 17

• Manufacturer Part Number: xwm8722eds
• Description: Stereo Dac With Integrated Tone Generator And Line/variable Level Outputs
• Manufacturer: ETC-unknow

WM8722
REGISTER 0/1
REGISTER 2
DAC OUTPUT ATTENUATION
A digital attenuator is provided to allow the levels of DAC signals to be attenuated in the digital
domain.
Register 0 (A[1:0] = 00) is used to control left channel attenuation. Bits 0-7 (AL[7:0]) are used to
determine the attenuation level. The level of attenuation is given by:
Attenuation = [20.log10 (Attenuation_Data/255)] dB
Bit 8 in register 0 (LDL) is used to control the loading of attenuation data in B[7:0]. When LDL is set
to 0, attenuation data will be loaded into AL[7:0], but it will not affect the attenuation level until LDL is
set to 1. LDR in register 1 has the same function for right channel attenuation.
Attenuation levels are controlled by setting the register set AL[7:0] (left channel) or AR[7:0] (right
channel). Attenuation levels are given in Table 7.
Table 7 Attenuation Control Levels
Register 1 (A[1:0] = 01)is used to control right channel attenuation in a similar manner.
SOFT MUTE
Soft mute is controlled by setting bit 0 in register 2 (A[1:0]=10). A high level on bit 0 will cause the
DAC outputs to be muted, the effect of which is to ramp the signal down in the digital domain so that
there is no discernible click.
DIGITAL DE-EMPHASIS
Bit 1 (DE) in register 2 (A[1:0]=10) is used to control digital de-emphasis. A low level on bit 1
disables de-emphasis whilst a high level enables de-emphasis.
POWER OFF CONTROL
Bit 2 (PWD) in register 2 is used for operation control. With PWD = low (default) the device functions
normally. With PWD = high the device is disabled and the outputs are held at midrail. Current
consumption of the digital section is minimised, but analogue bias sections remain active in order to
preserve DC levels.
INPUT WORD RESOLUTION
Bits 3 and 4 of register 2 (IW[1:0]) are used to determine the input word resolution. The WM8722
supports 16-bit, 18-bit, 20-bit and 24-bit word formats.
Table 8 Input Data Resolution
BIT 4 (IW1)
0
0
1
1
AX[7:0]
FEh
FFh
00h
01h
:
:
:
BIT 3 (IW0)
0
1
0
1
ATTENUATION LEVEL
-
16-bit Data Word
20-bit Data Word
24-bit Data Word
18-bit Data Word
INPUT RESOLUTION
-48.16 dB
-0.034 dB
dB (Mute)
0dB
:
:
:
AI Rev 2.1 June 2001
Advanced Information
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