TC236

680-

× 500-PIXEL CCD IMAGE SENSOR

SOCS043A – JUNE 1994 – REVISED NOVEMBER 1994

3

POST OFFICE BOX 655303

Terminal Functions

TERMINAL

I/O

DESCRIPTION

NAME

NO.

I/O

DESCRIPTION

ADB

4

I

Supply voltage for amplifier-drain bias

IAG1

12

I

Image-area gate 1

IAG2

3

I

Image-area gate 2

ODB

2

I

Supply voltage for overflow-drain antiblooming bias

OUT1

6

O

Output signal 1

OUT2

5

O

Output signal 2

RST

7

I

Reset gate

SAG

10, 11

I

Storage-area gate

SRG

8

I

Serial-register gate

SUB

1, 9

Substrate

detailed description

The TC236 consists of four basic functional blocks: the image-sensing area, the image-storage area, the serial

register gates, and the low-noise signal processing amplifier block with charge-detection nodes and

independent resets. The location of each of these blocks is identified in the functional block diagram.

image-sensing and storage areas

Figure 1 and Figure 2 show top views of the image-sensing and storage-area elements. As light enters the

silicon in the image-sensing area, free electrons are generated in both wells and collected in the virtual wells

of the sensing elements. The color sensitivity is obtained by manufacturing a mosaic color filter directly onto the

photosites of the image-sensing area (see Figure 3 for a mapping of the filter topology). Blooming protection

is provided by applying a dc bias to the overflow-drain bias pin. If it is necessary to clear the image before

beginning a new integration time (for implementation of electronic fixed shutter or electronic auto-iris), it is

possible to do so by applying a pulse at least 1

µs in duration to the overflow-drain bias. After integration is

complete, the charge is transferred into the storage area; the transfer timing is dependent on whether the

readout mode is interlace or progressive scan. If the progressive-scan readout mode is selected, the readout

may be performed normally with one register or high speed by using both registers (see Figure 4 through

Figure 6 for the interlace and progressive-scan readout modes).

There are 22 columns at the left edge of the image-sensing area that are shielded from incident light; these

elements provide the dark reference used in subsequent video-processing circuits to restore the video black

level. There are also four dark lines between the image-sensing and the image-storage area that prevent charge

leakage from the image-sensing area into the image-storage area.