AD9925BBCZ datasheet(21/96 Pages) AD

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AD9925

Rev. A | Page 21 of 96

HBLK

SPECIAL H-BLANK PATTERN IS CREATED USING MULTIPLE HBLK TOGGLE POSITIONS

H1/H3

H2/H4

TOG1

TOG2

TOG3

TOG4

TOG5

TOG6

Figure 26. Generating Special HBLK Patterns

Increasing H-Clock Width during HBLK

The AD9925 will also allow the H1 to H4 pulse width to be

increased during the HBLK interval. The H-clock pu

can increase by reducing the H-clock frequency (see Figure 27).

he HBLKWIDTH register, at Bank 1 Address 0x38, is a 3-bit

1/4, 1/6, 1/8, 1/10, 1/12, or 1/14. The reduced frequen

only occur for H1 to H4 pulses that are located within t

BLK area.

lse width

cy will

Table 12. HBLK Width Register

Length

Range

Description

HBLKWIDTH

3 b

1 to 1/14

Controls H1 to H4 widt

during HBLK as a frac-

tion of pixel rate

0: same frequency as

pixel rate

1: 1/2 pixel frequency,

i.e., doubles the H1 to H4

pulse width

6: 1/12 pixel frequency

7: 1/14 pixel frequency

2: 1/4 pixel frequency

3: 1/6 pixel frequency

4: 1/8 pixel frequency

5: 1/10 pixel frequency

HORIZONTAL TIMING SEQUENCE EXAMPLE

Figure 28 shows an exampl CCD layout. The horizontal register

ummy pixels, which will occur on each line clocked

from the CCD. In the vertical direction, there are 10 optical black

(OB) lines at the front of the readout and 2 at the back of the

readout. The horizontal direction has 4 OB pixels in the front

back.

Figure 29 shows the basic sequence layout to be used during the

line

contains 28 d

and 48 in the

effective pixel readout. The 48 OB pixels at the end of each

are used for the CLPOB signals. PBLK is optional and is often

used to blank the digital outputs during the noneffective CCD

pixels. HBLK is used during the vertical shift interval. The

HBLK, CLPOB, and PBLK parameters are programmed in the

vertical sequence registers.

More elaborate clamping schemes may be used, such as addin

in a separate sequence to clamp during the entire shield OB

lines. This requires configuring a separate vertical sequence for

reading out the OB lines.

HBLK

H-CLOCK FREQUENCY CAN BE REDUCED DURING HBLK BY 1/2 (AS

SHOWN), 1/4, 1/6, 1/8, 1/10, 1/12, OR 1/14 USING HBLKWIDTH REGISTER

H1/H3

H2/H4

1/FPIX

2 × (1/FPIX)

Figure 27. Generating Wide H-Clock Pulses during HBLK Interval

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