TC237B

680-

× 500-PIXEL CCD IMAGE SENSOR

SOCS063 – APRIL 2001

9

POST OFFICE BOX 655303

serial registers

The storage area gate and serial gate(s) are used to transfer charge line-by-line from the storage area into the

serial register(s). Depending on the readout mode, one or both serial registers are used. If both are used, the

registers are read out in parallel.

readout and video processing

After transfer into the serial register(s), the pixels are clocked out and sensed by a charge detection node. The

node must be reset to a reference level before the next pixel is placed onto it. The timing for the serial-register

readout, which includes the external pixel clamp and sample-and-hold signals needed to implement correlated

double sampling, is shown in Figure 7. As charge is transferred onto the detection node, the potential of the node

changes in proportion to the amount of the charge received. The change is sensed by an MOS transistor; after

proper buffering, the signal is supplied to the output terminal of the image sensor. Figure 8 shows the circuit

diagram of the charge detection node and output amplifier. The detection nodes and amplifiers are placed a

short distance from the edge of the storage area; therefore, each serial register contains 4 dummy elements

that are used to span the distance between the serial registers and the amplifiers.

OUT

RST

SRG

S/H

PCMP

Figure 7. Serial Readout and Video-Processing Timing

VOUT

ADB

VREF

Reset

CCD Channel

QR

Q1

Q2

Figure 8. Output Amplifier and Charge Detection Node