W6662CF Просмотр технического описания (PDF) - Winbond

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W6662CF

SCANNER ANALOG FRONT END

Winbond 

Preliminary W6662CF

SEL1 = 0, SEL0 = 1 is red channel of gain register and offset register selected.

SEL1 = 1, SEL0 = 0 is green channel of gain register and offset register selected.

SEL1 = 1, SEL0 = 1 is blue channel of gain register and offset register selected.

SEL1 = 0, SEL0 = 0 is reserved.

6.3 CDS vs S&H Mode

"CDS" stands for "correlated double sampling". It is used to reduce noise generated in CCD source

and to decrease the sampling error which induced from clampping voltage error. CDS takes two step

to sample a CCD's output pixel. In the first step, the reset level of CCD output is sampled and hold by

S/H1 at the falling edge of CDSCK1 signal. In the second step, the data signal of CCD output is

sampled and hold by S/H2 at the falling edge of CDSCK2 signal. The CDS output voltage is obtained

from the voltage difference of the outputs of S/H1 and S/H2.

In S&H mode, the data signal of CIS output is sampled and hold by S/H1 at the falling edge of

CDSCK2 signal and the output voltage is obtained from the voltage difference of the outputs of S/H1

and CISREF pin. Figure 6-3 shows the equivalent circuits of CDS and S&H mode processing.

From

I/P

MUX

S/H1

+

CDSCK1

S/H2

-

(a) CDS Mode.

CDSCK2

To

Gain/Offset

Adjust

From

I/P

MUX

From

CISREF

pin

S/H1

+

CDSCK2

-

(b) S&H Mode.

To

Gain/Offset

Adjust

Fig. 6-3 The Equivalent Circuit of CDS and S&H Mode.

6.4 Gain/Offset Adjustment

The analog input signal after CDS or S&H processed is amplified by PGA gain adjustment and then

shifted by offset value. The offset value will not affected by the PGA gain adjustment.

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