AD9923ABBCZ datasheet(24/88 Pages) AD

24 / 88 page

AD9923A

Rev. 0 | Page 24 of 88

Increasing H-Clock Width During HBLK

The AD9923A allows the H1 to H4 pulse width to be increased

during the HBLK interval. The H-clock pulse width can in-

crease by reducing the H-clock frequency (see Table 13).

The HBLKWIDTH register (Register 0x35, Bits[6:4]) is a 3-bit

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

occurs for H1 to H4 pulses that are located within the HBLK area.

Horizontal Timing Sequence Example

Figure 33 shows an example of a CCD layout. The horizontal

clocked from the CCD. In the vertical direction, there are 10

optical black (OB) lines at the front of the readout and two at

the back of the readout. The horizontal direction has four OB

pixels in the front and 48 OB pixels in the back.

Figure 34 shows the basic sequence layout to use during the

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

are used for CLPOB signals. PBLK is optional and it 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 V-sequence registers. More elaborate clamping schemes can

be used, such as adding a separate sequence to clamp during the

entire line of OB pixels. This requires configuring a separate

V-sequence for reading the OB lines.

The CLPMASKSTART and CLPMASKEND registers can be used

to disable the CLPOB on a few lines without affecting the setup of

the clamp sequences.

HORIZONTAL CCD REGISTER

EFFECTIVE IMAGE AREA

28 DUMMY PIXELS

48 OB PIXELS

4 OB PIXELS

10 VERTICAL

OB LINES

2 VERTICAL

OB LINES

Figure 33. CCD Configuration Example

Table 13. HBLK Width Register

Length (Bits)

Range

Description

HBLKWIDTH

1× to 1/14× pixel rate

Controls H1 to H4 width during HBLK as a fraction of pixel rate

0: same frequency as the pixel rate

1: 1/2 pixel frequency, that is, doubles the H1 to H4 pulse width

2: 1/4 pixel frequency

3: 1/6 pixel frequency

4: 1/8 pixel frequency

5: 1/10 pixel frequency

6: 1/12 pixel frequency

7: 1/14 pixel frequency

VERTICAL SHIFT

VERT. SHIFT

CCDIN

SHP

SHD

HL/H1/H3

H2/H4

HBLK

PBLK

CLPOB

OPTICAL BLACK

DUMMY

EFFECTIVE PIXELS

OPTICAL BLACK

Figure 34. Horizontal Sequence Example

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