CS7615 datasheet(8/36 Pages) CIRRUS

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CS7615

DS231PP6

CCD Timing Generator

The CCD timing and control signal outputs are dic-

tated by the programmable register settings. This

allows for compatibility with a variety of CCDs.

The HSYNC signal is also output for use in a gen-

lock configuration. The open-drain HCLK can be

used to clock dc-dc voltage converters which are

typically used to generate the CCD imager bias

voltages. The following description explains the

various output signals provided to the vertical driv-

er and CCD as well as the programmable parame-

ters that may be set to control these signals.

HREF* - horizontal reference signal. It stays

high during the active video portion of the line.

HENB* - Horizontal shift register clock enable

signal. Enables H1 and H2 out of analog tim-

ing.

CLAMP* - Black clamp signal provided to the

ADC.

V1X, V2X, V3X, V4X - Vertical register shift

clock. Used both during vertical transfer and

charge read out.

VH1X, VH3X - CCD charge read out pulse.

HCLK - Signal used by the dc - dc converter. In

the normal mode, it is the same as HREF; In

fast mode, it operates at about 16× of the hori-

zontal line frequency and is reset at the begin-

ning of HREF.

HSYNC - Horizontal sync signal.

OFDX - Overflow drain control clock. This

signal sets the electronic shutter speed.

VRST - Vertical field reset signal.

VREF* - Vertical reference signal. It is high

during the active video lines.

*Internal signal on the CS7615 - not a chip output.

Vertical Timing Specifications

The CCD array is read out alternately as odd and

even fields with interlaced horizontal lines. Thus

each field has half the total number of horizontal

rows. Table 1 specifies the programmable vertical

timings which are defined in Figure 8. The timings

vary based on odd or even field, 525 or 625 line

CCD, and the manufacturer.

Horizontal Timing Specifications

Each horizontal row of the CCD is divided into

several regions corresponding to the type of pixels

present. Different CCDs have different numbers of

pixels in each region and the timing signals must

take this into account. The different pixel types in-

clude optical black pixels (front and rear), dummy

pixels, active video pixels, and blank video. The

horizontal timing for the CCD is based on main-

taining a fixed 63.5

µs horizontal line time.

CLK2XO

CLKO

DO[0..9]

Figure 7. CS7615 Output Data and Clocks

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