Datasheet
PCM1741
12
SBAS175
REGISTER DEFINITIONS
B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
Register 16 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT17 AT16 AT15 AT14 AT13 AT12 AT11 AT10
Register 17 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT27 AT26 AT25 AT24 AT23 AT22 AT21 AT20
ATx[7:0] Digital Attenuation Level Setting
where x = 1 or 2, corresponding to the DAC output V
OUT
L (x = 1) and V
OUT
R (x = 2).
Default Value: 1111 1111
B
Each DAC channel (V
OUT
L and V
OUT
R) includes a digital attenuator function. The attenuation level may be
set from 0dB to –63dB, in 0.5dB steps. Changes in attentuator levels are made by incrementing or
decrementing, by one step (0.5dB), for every 8/f
S
time interval until the programmed attenuator setting is
reached. Alternatively, the attenuator level may be set to infinite attenuation (or mute). The attenuation data
for each channel can be set individually.
The attenuation level may be set using the formula below.
Attenuation Level (dB) = 0.5 (ATx[7:0]
DEC
– 255)
where: ATx[7:0]
DEC
= 0 through 255
for: ATx[7:0]
DEC
= 0 through 128, the attenuator is set to infinite attenuation.
The following table shows attenuator levels for various settings.
ATx[7:0] Decimal Value Attenuator Level Setting
1111 1111
B
255 0dB, No Attenuation (default)
1111 1110
B
254 –0.5dB
1111 1101
B
253 –1.0dB
1000 0011
B
131 –62.0dB
1000 0010
B
130 –62.5dB
1000 0001
B
129 –63.0dB
1000 0000
B
128 Mute
•••
•••
•••
0000 0000
B
0 Mute
B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
Register 18 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 RSV OVER RSV RSV RSV RSV MUT2 MUT1
MUTx Soft Mute Control
Where x = 1 or 2, corresponding to the DAC output V
OUT
L (x = 1) and V
OUT
R (x = 2).
Default Value: 0
MUTx = 0 Mute Disabled (default)
MUTx = 1 Mute Enabled
The mute bits, MUT1 and MUT2, are used to enable or disable the Soft Mute function for the corresponding
DAC outputs, V
OUT
L and V
OUT
R. The Soft Mute function is incorporated into the digital attenuators. When
Mute is disabled (MUTx = 0), the attenuator and DAC operate normally. When Mute is enabled by setting
MUTx = 1, the digital attenuator for the corresponding output will be decreased from the current setting to
the infinite attenuation setting, one attenuator step (0.5dB) at a time. This provides a “pop”-free muting of the
DAC output. By setting MUTx = 0, the attenuator will be increased one step at a time to a previously
programmed attenuation level.
OVER Oversampling Rate Control
Default Value: 0
OVER = 0 64x Oversampling (default)
OVER = 1 128x Oversampling
The OVER bit is used to control the oversampling rate of the delta-sigma DACs.