AD9805JS datasheet(15/24 Pages) AD

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AD9807/AD9805

–15–

REV. 0

R (n–2)

G (n–2)

B (n–2)

R (n–1)

G (n–1)

B (n–1)

R (n)

PIXEL n

PIXEL n+1

PIXEL n+2

R, G, B

RIN, GIN, BIN

CDSCLK1

CDSCLK2

ADCCLK

DATA<11:0>

G (n+1)

B (n+1)

R (n+2)

G (n+2)

B (n+2)

R (n+3)

GAIN<n:0>

GAIN<m:0>

R (n)

G (n)

B (n)

R (n+1)

Figure 12. DOUT Latency, 3-Channel CDS Mode

tOD

tHZ

tEDV

ADCCLK

DATA<11:0>

OEB

Figure 11. Digital Output Timing

is inverted and amplified by the PGA; the setting in the corre-

sponding PGA Gain Register determines the gain of the PGA.

The output from the PGA is then routed through a high speed

multiplexer to a 12-bit A/D converter (10-bit for AD9805) for

digitization; the multiplexer does cycle in this mode. After

digitization, the data is modified by the amount indicated in

the Even Offset Registers. A digital subtracter allows additional

pixel rate offset modification of the signal based on the values

written to the OFFSET data bus. Finally, a digital multiplier

allows pixel rate gain modification of the signal based on the

values written to the GAIN data bus. Latency is 6 ADCCLK

cycles (7 cycles for the gain and offset bus; see Figure 14).

The state of STRTLN is evaluated on the rising edges of

ADCCLK. When STRTLN is low, the internal circuitry is

reset on the next rising edge of ADCCLK; the odd/even

circuitry is configured to expect even pixels.

This feature has been included to accommodate the use of the

part with an area CCD (Bayer Mode). The mode is initiated by

writing a one to the LSB of the register at Address 7 (see Figure

21). The write to enable the mode should be performed when

the STRTLN input is inactive (low) and the ADCCLK is running.

The first pixel after an active edge on STRTLN will be a green

pixel. All pixels in Bayer Mode are even and use the even offset

registers. The line will continue alternating GRGRGR pixels

until STRTLN goes inactive. The next line will be BGBGBG

pixels (the first pixel after the active STRTLN edge being blue).

Line type will then alternate between GRGRGR and BGBGBG

type. To reset the next line to GRGRGR type at the start of the

next frame/image, rewrite the Bayer mode enable bit to a one

during the inactive STRTLN period. All red and blue pixels

pass through the blue channel of the part and use the blue PGA

and offset registers. To use a different offset/PGA gain value the

line type pass through the green channel.

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