AD9920A
Rev. B | Page 22 of 112
DIGITAL DATA OUTPUTS
The AD9920A data output and DCLK phase are programmable
using the DOUTPHASE registers (Address 0x39, Bits[13:0]).
DOUTPHASEP (Bits[5:0]) selects any edge location from 0 to
63, as shown in
Figure 25. DOUTPHASEN (Bits[13:8]) does
not actually program the phase of the data outputs but is used
internally and should always be programmed to a value of
DOUTPHASEP plus 32 edges. For example, if DOUTPHASEP
is set to 0, DOUTPHASEN should be set to 32 (0x20).
Normally, the data output and DCLK signals track in phase,
based on the contents of the DOUTPHASE registers. The DCLK
output phase can also be held fixed with respect to the data out-
puts by setting the DCLKMODE register high (Address 0x39,
Bit 16). In this mode, the DCLK output remains at a fixed phase
equal to a delayed version of CLI, and the data output phase
remains programmable.
The pipeline delay through the AD9920A is shown in
Figure 26.
After the CCD input is sampled by SHD, there is a 16-cycle
delay until the data is available.
P[0]
P[64] = P[0]
PIXEL
PERIOD
P[16]
P[32]
P[48]
DOUT
DCLK
tOD
NOTES
1. DATA OUTPUT (DOUT) AND DCLK PHASE ARE ADJUSTABLE WITH RESPECT TO THE PIXEL PERIOD.
2. WITHIN ONE CLOCK PERIOD, THE DATA TRANSITION CAN BE PROGRAMMED TO 64 DIFFERENT LOCATIONS.
3. DCLK CAN BE INVERTED WITH RESPECT TO DOUT BY USING THE DCLKINV REGISTER.
06
87
8-
02
5
Figure 25. Digital Output Phase Adjustment Using DOUTPHASEP Register
NOTES
1. TIMING VALUES SHOWN ARE SHDLOC = 0, WITH DCLKMODE = 0.
2. HIGHER VALUES OF SHD AND/OR DOUTPHASE SHIFT DOUT TRANSITION TO THE RIGHT, WITH RESPECT TO CLI LOCATION.
3. RECOMMENDED VALUE FOR DOUTPHASE IS TO USE SHPLOC OR UP TO 15 EDGES FOLLOWING SHPLOC.
DCLK
DOUT
CCDIN
CLI
SHD
(INTERNAL)
ADC DOUT
(INTERNAL)
NN + 2
N + 1
N + 3
N + 13
N + 12
N + 11
N + 10
N + 9
N + 8
N + 7
N + 6
N + 5
N + 4
N + 14
SAMPLE PIXEL N
N + 16
N + 17
N + 15
N – 14
N – 4
N – 5
N – 6
N – 7
N – 8
N – 9
N – 10
N – 11
N – 12
N – 13
N – 3
N – 2
N – 1
N
N + 1
N – 15
N – 16
N – 17
tCLIDLY
PIPELINE LATENCY = 16 CYCLES
N – 14
N – 4
N – 5
N – 6
N – 7
N – 8
N – 9
N – 10
N – 11
N – 12
N – 13
N – 3
N – 2
N – 1
N
N + 1
N – 15
N – 16
N – 17
tDOUTINH
068
78-
026
Figure 26. Digital Data Output Pipeline Delay