WM8720
Production Data
AX[7:0]
ATTENUATION LEVEL
00(hex)
- ∞dB (mute)
01(hex)
-48.16dB
:
:
:
:
:
:
Fe(hex)
FF(hex)
-0.07dB
0dB
Table 9 Attenuation Control Levels
Bit 8 in register 0 (LDL) is used to control the loading of attenuation data in AL[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.
Register 1 (A[1:0] = 01) is used to control right channel attenuation in a similar manner.
Bit 2 in register 3 (A1[1:0] = 11) is used to control the attenuator (ATC). When ATC is high, the
attenuation data loaded in program register 0 is used for both the left and the right channels. When
ATC is low, the attenuation data for each register is applied separately to left and right channels.
LEFT AND RIGHT DACS SOFT MUTE CONTROL
Soft mute is controlled by setting bit MU, register 2:bit 0. A high level on MU (MU = 1) will cause the
output to be muted, the effect of which is to ramp the signal down in the digital domain so that there
is no discernible click. This can be seen in Figure 6 Mute Circuit Operation.
DE-EMPHASIS CONTROL
Bit 1 (DE) in register 2 is used to control digital de-emphasis. A low level on bit 1 (DE = 0) disables
de-emphasis whilst a high level enables de-emphasis (DE = 1). De-emphasis applied to the filters
shapes the frequency response of the digital filter according to the input sample frequency.
LEFT AND RIGHT DACS OPERATION CONTROL
Bit 2 (OPE) in register 2 is used for operation control. With OPE = 0 (default) the device functions
normally. With OPE = 1 the device is disabled and the outputs are held at midrail. Current
consumption of the digital section is minimized, but analogue sections remain active in order to
preserve DC levels.
INPUT AUDIO WORD RESOLUTION
WM8720 allows maximum flexibility over the control of the audio data interface, allowing selection of
format type, word length, and sample rates. Bits 3 and 4 of register 2 (IW[1:0]) are used to determine
the input word resolution. WM8720 supports 16-bit, 18-bit, 20-bit and 24-bit formats as described in
Table 10.
BIT 4 (IW1)
BIT 3 (IW0)
INPUT RESOLUTION
16-bit data word
20-bit data word
24-bit data word
18-bit data word
0
0
1
0
1
0
1
1
Table 10 Input Data Resolution
PD Rev 4.0. February 2005
13
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
