AD9923ABBCZ datasheet(35/88 Pages) AD

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AD9923A

Rev. 0 | Page 35 of 88

XV1

XV2

XV13

VSG

SECOND VPAT GROUP

START POSITION FOR SECOND VPAT GROUP

USES VSTARTSECOND REGISTER

Figure 47. Example of Second VPAT Group During Sensor Gate Line

XV1 TO XV13

REGION 1: SWEEP REGION

LINE 0

LINE 1

REGION 0

REGION 2

LINE 24

LINE 25

LINE 2

SCP 1

SCP 2

Figure 48. Example of Sweep Region for High Speed Vertical Shift

Figure 48 shows an example of sweep mode operation. The

number of required vertical pulses depends on the vertical

resolution of the CCD. The XV1 to XV13 output signals are

generated using the V-pattern registers (shown in Table 14).

A single pulse is created using the polarity and toggle position

registers. The number of repetitions is then programmed to

match the number of vertical shifts required by the CCD.

Repetitions are programmed in the V-sequence registers using

the VREP registers. This produces a pulse train of the appropriate

length. Normally, the pulse train is truncated at the end of the

HD line length, but with sweep mode enabled, the HD

boundaries are ignored. In Figure 48, the sweep region occupies

23 HD lines. After the sweep mode region is complete, normal

sequence operation resumes in the next region. When using

sweep mode, set the region boundaries, using the sequence

change position registers, to the appropriate lines to prevent the

sweep operation from overlapping with the next V-sequence.

Multiplier Mode

To generate very wide vertical timing pulses, a vertical region

can be configured into a multiplier region. This mode uses the

V-pattern registers in a slightly different manner. Multiplier mode

can be used to support unusual CCD timing requirements, such

as vertical pulses that are wider than the 13-bit V-pattern toggle

position counter.

The start polarity and toggle positions are used in the same

manner as the standard VPAT group programming, but the

VLEN register is used differently. Instead of using the pixel

counter (HD counter) to specify the toggle position locations

(XVTOG1, XVTOG2, XVTOG3, XVTOG4, XVTOG5, and

XVTOG6) of the VPAT group, the VLEN value is multiplied by

the XVTOG value to allow very long pulses to be generated. To

calculate the exact toggle position, counted in pixels after the

start position, use the following equation:

Multiplier Mode Toggle Position = XVTOG × VLEN

Because the XVTOG value is multiplied by the VLEN value, the

resolution of the toggle position placement is reduced.

If VLEN = 4, the toggle position accuracy is reduced to four

pixel steps, instead of single pixel steps. Table 18 summarizes

how the VPAT group registers are used in multiplier mode

operation. In multiplier mode, the VREP registers should be

programmed to the value of the highest toggle position.

The example shown in Figure 49 illustrates this operation. The

first toggle position is 2, and the second toggle position is 9. In

nonmultiplier mode, this causes the V-sequence to toggle at

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