Datasheet

PCM1690
www.ti.com .............................................................................................................................................. SBAS448A – OCTOBER 2008 – REVISED JANUARY 2009
DEC HEX B7 B6 B5 B4 B3 B2 B1 B0
71 47 RSV RSV RSV RSV RSV RSV RSV RSV
72 48 ATDA17 ATDA16 ATDA15 ATDA14 ATDA13 ATDA12 ATDA11 ATDA10
73 49 ATDA27 ATDA26 ATDA25 ATDA24 ATDA23 ATDA22 ATDA21 ATDA20
74 4A ATDA37 ATDA36 ATDA35 ATDA34 ATDA33 ATDA32 ATDA31 ATDA30
75 4B ATDA47 ATDA46 ATDA45 ATDA44 ATDA43 ATDA42 ATDA41 ATDA40
76 4C ATDA57 ATDA56 ATDA55 ATDA54 ATDA53 ATDA52 ATDA51 ATDA50
77 4D ATDA67 ATDA66 ATDA65 ATDA64 ATDA63 ATDA62 ATDA61 ATDA60
78 4E ATDA77 ATDA76 ATDA75 ATDA74 ATDA73 ATDA72 ATDA71 ATDA70
79 4F ATDA87 ATDA86 ATDA85 ATDA84 ATDA83 ATDA82 ATDA81 ATDA80
RSV Reserved
Reserved; do not use.
ATDAx[7:0] Digital attenuation level setting
Where x = 1 to 8, corresponding to the DAC output (V
OUT
x).
Each DAC output (V
OUT
1 through V
OUT
8) has a digital attenuation function. The attenuation level
can be set from 0 dB to R dB, in S-dB steps. Changes in attenuator levels are made by
incrementing or decrementing one step (S dB) for every 8/f
S
time interval until the programmed
attenuator setting is reached. Alternatively, the attenuation level can be set to infinite attenuation
(or mute). R (Range) and S (Step) is – 63 and 0.5 for DAMS = 0 and – 100 and 1.0 for DAMS = 1,
respectively. The DAMS bit is defined in Register 70 (46h). Table 17 shows attenuation levels for
various settings.
The attenuation level for each channel can be set individually using the following formula:
Attenuation level (dB) = S × (ATDAx[7:0]
DEC
– 255)
where ATDAx[7:0]
DEC
= 0 through 255.
For ATDAx[7:0]
DEC
= 0 through 128 with DAMS = 0 or 0 through 154 with DAMS = 1, attenuation
is set to infinite attenuation (mute).
Default value: 1111 1111.
Table 17. Attenuation Levels for Various Settings
ATDAx[7:0] ATTENUATION LEVEL SETTING
BINARY DECIMAL DAMS = 0 DAMS = 1
1111 1111 255 0 dB, no attenuation (default) 0 dB, no attenuation (default)
1111 1110 254 – 0.5 dB – 1 dB
1111 1101 253 – 1.0 dB – 2 dB
... ... ... ...
1001 1100 156 – 45.9 dB – 99 dB
1001 1011 155 – 50.0 dB – 100 dB
1001 1010 154 – 50.5 dB Mute
... ... ... ...
1000 0010 130 – 62.5 dB Mute
1000 0001 129 – 63.0 dB Mute
0000 0000 128 Mute Mute
... ... ... ...
0000 0000 0 Mute Mute
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