XRD9825 데이터 시트보기 (PDF) - Exar Corporation

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XRD9825

16-Bit Linear CIS/CCD Sensor Signal Processor with Serial Control

Exar Corporation 

XRD9825

CIS Rotating Gain and Offset

Line-By-Line (Md 11)

CIS

Red Pixel Line Scan

Grn Pixel Line Scan

Blu Pixel Line Scan

ADCCLK

SYNCH

GAIN/

OFFSET

tsypw

tsa

Red Gain/Offset Cycle

Grn Gain/Offset Cycle

LD

Reset Internal Mux Color to Red Channel (LD = 110YYYYYY11)

Note: Y = Previous State

Blu Gain/Offset Cycle

Tri-State (SYNCH = LO)

Figure 12. Timing Diagram for Figure 11

CCD Configuration (Charge Coupled Device)

Mode 1. AC Coupled

In the CCD configuration of operation, an external

capacitor needs to be chosen according to the equa-

tions below. The typical value for the external capacitor

is 100pF. This value should be adjusted according to

the time constant (Tc) needed in a particular applica-

tion. The CLAMP pin has an internal 150 ohm imped-

ance (R ) which is in series with the external capacitor

INT

(CEXT).

Therefore, Tc =1/RINTCEXT

If the input to the external capacitor has a load imped-

ance (REXT), then

Tc=1/(RINT+REXT)CEXT

When CLAMP (clamp) pin is set high an internal switch

allows one side of the external capacitor to be set to

VRT (Figure 13). This value corresponds to the black

reference of the CCD. When the CLAMP pin is set back

to low, the ADC samples the video signal with respect

to the black reference. The difference between the

black reference and the video signal is the actual pixel

value of the video content. Since this value is refer-

enced to the top ladder reference voltage of the ADC a

zero input signal would yield a full scale output code.

Therefore, the output of the conversion is inverted

(internally) to correspond to zero scale output code.

Rev. 1.00

18

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