AD9898
VSUB CONTROL
The CCD readout bias (VSUB) can be programmed to accom-
modate different CCDs. VSUB ON and OFF toggle positions
and polarity are controlled using VSUBTOG (Addr 0x0D) and
VSUBPOL (Addr 0x0D) registers, respectively, as described in
Table XXIV. Since the VSUBTOG is an 11-bit register, the
VSUB ON position is programmable within any line. Figure 43
shows an example of controlling VSUB using these registers.
Table XXIV. VSUB Registers
Register Bit Register Range
Name
Width Type (Lines) Description
VSUBPOL 1
VSUBTOG 11
Control
(0 = Low, 1 = High)
Control 0–2048 VSUB Toggle Position
VSUB Placement and Polarity
Figure 43 shows the sequence of events for programming the
VSUB ON and OFF toggle positions and polarity.
1. Program VSUBTOG = 2 and VSUBPOL = 1.
2. Since VSUBTOG and VSUBPOL are VD synchronous type
registers, the falling edge of VD will update the serial writes
from Step 1 here.
3. VSUB will be asserted high after two HD cycles.
4. Program VSUBTOG = 3 and VSUBPOL = 0.
5. Since VSUBTOG and VSUBPOL are VD synchronous type
registers, the falling edge of VD will update the serial writes
from Step 4 here.
6. VSUB will be asserted low after three HD cycles.
1
SERIAL
WRITES
2
VD
HD
VSUB
3
2 LINES
4
Figure 43. VSUB Timing Example
5
6
3 LINES
REV. 0
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