XRD98L59 Datasheet, PDF (20/37 Pages) Exar Corporation – CCD Image Digitizers with CDS, PGA and 10-Bit A/D

XRD98L59
Active Video
Pixels
CCD
Signal
CAL
Internal
DC Restore Time
Internal Black Level
Calibration Time
(D1 = 0)
CLAMP
End of Line N
OB Pixels
t_CAL (min 5 Pixels)
4 Pixels
t_CAL - 4 Pixels
Vertical Shift
Start of Line N+1
Dummy &
OB Pixels
Active Video Pixels
Figure 13. Example of Minimum Timing Requirements for CAL Only Line Calibration Mode
(CAL and CLAMP Polarity are Serial Port Programmable)
SDI = 0011 0000 0000
Most timing generators (TG’s) define the start of line and
end of line OB pixels on the CCD array. The CAL timing
signal should always be active for the greatest number of
OB pixels possible, either during start or end of line. The
more OB pixels that the XRD98L59 can use for its auto-
calibration, the faster it can achieve and maintain calibra-
tion.
While in “CAL ONLY” Line Calibration Timing Mode,
CLAMP needs to be held inactive during the output of
active video and OB pixels from the CCD. Figure 13
shows the minimum timing requirements for the “CAL
ONLY” Line Calibration Timing Mode. The inactive
state for CLAMP depends on the CLAMP-Polarity
setting (Clock Reg bit D1).
Vertical Shift Reject
The CLAMP input can be used to implement a Vertical
Shift Reject function while in “CAL ONLY” Line Cali-
bration Timing Mode. The Vertical Shift Rejection,
also called preblanking, can be used to reject and any
large transients present in the CCD output during the
vertical clocking.
To implement the Vertical Shift Reject (Preblanking)
function on the XRD98L59 the CLAMP opt bit must be
low (Clock Reg D4=0) and the CLAMP input driven
with the preblanking timing signal. The preblanking
timing signal, commonly called PBLK, is generated by
the system timing generator and defines the vertical
shift of the CCD (see Figure 13a). The preblanking
pulse opens the Reset Reject Switches internal to the
XRD98L59, see Figure 5, thereby rejecting any
transients in the CCD output while the vertical shifting
is being done.
Rev. 2.00
20