
AD9826
–15–
REV. A
MUX Configuration Register
T he MUX Configuration Register controls the sampling chan-
nel order and the 2-Channel Mode configuration in the AD9826.
Bits D8 and D3–D0 should always be set low. Bit D7 is used
when operating in 3-Channel or 2-Channel Mode. Setting Bit
D7 high will sequence the MUX to sample the Red channel
first, then the Green channel, and then the Blue channel. When
in 3-channel mode, the CDSCLK2 pulse always resets the MUX
to sample the Red channel first (see Figure 11). When Bit D7 is
set low, the channel order is reversed to Blue first, Green sec-
ond, and Red third. T he CDSCLK 2 pulse will always reset the
MUX to sample the Blue channel first. Bits D6, D5, and D4 are
used when operating in 1 or 2-Channel Mode. Bit D6 is set high
to sample the Red channel. Bit D5 is set high to sample the
Green channel. Bit D4 is set high to sample the Blue channel.
T he MUX will remain stationary during 1-channel mode. T wo-
Channel Mode is selected by setting two of the channel select
Bits (D4–D6) high. T he MUX samples the channels in the
order selected by Bit D7.
PGA Gain Registers
T here are three PGA registers for individually programming the
gain in the Red, Green, and Blue channels. Bits D8, D7, and
D6 in each register must be set low, and Bits D5 through D0
control the gain range from 1
×
to 6
×
in 64 increments. See
Figure 17 for a graph of the PGA gain versus PGA register
code. T he coding for the PGA registers is straight binary, with
an all “zeros” word corresponding to the minimum gain setting
(1
×
) and an all “ones” word corresponding to the maximum
gain setting (6
×
).
Offset Registers
T here are three Offset Registers for individually programming
the offset in the Red, Green, and Blue channels. Bits D8 through
D0 control the offset range from –300 mV to +300 mV in 512
increments. T he coding for the Offset Registers is Sign Mag-
nitude, with D8 as the sign bit. T able V shows the offset range
as a function of the Bits D8 through D0.
T able III. MUX Configuration Register Settings
D
8
D7
D6
D5
D4
D3
D2
D1
D0
Set
to
0
MUX Order
Channel Select
Channel Select
Channel Select
Set
to
0
Set
to
0
Set
to
0
Set
to
0
1 = R-G-B
*
0 = B-G-R
1 = RED
*
0 = Off
1 = GREEN
0 = Off
*
1 = BLUE
0 = Off
*
*
Power-on default value.
T able IV. PGA Gain Register Settings
D8
D7
D6
D5
D4
D3
D2
D1
D0
Gain (V/V)
Gain (dB)
Set to 0
0
0
Set to 0
0
0
Set to 0
0
0
MSB
0
0
LSB
0
*
1
0
0
1
1
0
0
0
0
0
0
1.0
1.013
5.56
6.0
0.0
0.12
14.9
15.56
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
*
Power-on default value.
T able V. Offset Register Settings
D8
D7
D6
D5
D4
D3
D2
D1
D0
Offset (mV)
MSB
0
0
LSB
0
*
1
0
0
0
0
0
0
0
0
1
0
0
1
0
0
0
0
0
0
0
+1.2
+300
0
–1.2
–300
0
1
1
1
0
0
1
0
0
1
0
0
1
0
0
1
0
0
1
0
0
1
0
1
1
1
1
1
1
1
1
1
*
Power-on default value.