AD9992BBCZ datasheet(40/92 Pages) AD

40 / 92 page

AD9992

Rev. C | Page 40 of 92

REGION 0

FIELD SETTINGS:

1. SEQUENCE CHANGE POSITIONS (SCP0 TO SCP8) DEFINE EACH OF THE NINE AVAILABLE REGIONS IN THE FIELD.

2. SEQ0 TO SEQ8 SELECT THE DESIRED V-SEQUENCE FOR EACH REGION.

3. SGACTLINE1 REGISTER SELECTS WHICH HD LINE IN THE FIELD CONTAINS THE SENSOR GATE PULSE(S).

XV1 TO XVN

SCP1

SCP2

SEQ0

SEQ1

SCP3

SEQ2

SCP4

SEQ3

SCP5

SEQ4

SCP8

SEQ8

REGION 1

REGION 2

REGION 3

REGION 4

REGION 8

VSG

SGACTLINE1

SCP0

Figure 48. Complete Field Divided into Regions

XV1 TO XVN

REGION 1: SWEEP REGION

LINE 0

LINE 1

REGION 0

REGION 2

LINE 24

LINE 25

LINE 2

SCP1

SCP2

Figure 49. Example of Sweep Region for High Speed Vertical Shift

Sweep Mode Operation

The AD9992 contains an additional mode of vertical timing

operation called sweep mode. This mode is used to generate

a large number of repetitive pulses that span across multiple HD

lines. An example of where this mode is needed is at the start of

the CCD readout operation. At the end of the image exposure

before the image is transferred by the sensor gate pulses, the vertical

interline CCD registers should be free of all charge. This can be

accomplished by quickly shifting out any charge using a long

series of pulses from the vertical outputs. Depending on the vertical

resolution of the CCD, up to 3000 clock cycles may be needed

to shift the charge out of each vertical CCD line. This operation

spans across multiple HD line lengths. Normally, the AD9992

vertical timing must be contained within one HD line length,

but when sweep mode is enabled, the HD boundaries are

ignored until the region is finished. To enable sweep mode within

any region, program the appropriate SWEEP register to high.

Figure 49 shows an example of the sweep mode operation. The

number of vertical pulses needed depends on the vertical resolu-

tion of the CCD. The toggle positions for the XV1 to XV24

signals are generated using the V-pattern registers (shown in

Table 13). 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 into the V-sequence registers

(shown in Table 14) by 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 when sweep

mode is enabled for this region, the HD boundaries are ignored.

In Figure 49, 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, be sure to

set the region boundaries (using the sequence change positions)

to the appropriate lines to prevent the sweep operation from

overlapping the next V-sequence.

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