TC281

1036-

× 1010-PIXEL CCD IMAGE SENSOR

SOCS058B – JUNE 1996 – REVISED MAY 1999

6

POST OFFICE BOX 655303

IAG

~1

µs

Transfer The

First Line From

SA to AR

Transfer The

Second Line

Adding to The First

Each Additional Pulse

Bins One Additional Line

Serial Line Readout

SAG

TRG

SRG

RST

Figure 5. Special Modes of Operation: Binning

detailed description

The TC281 image sensor consists of five basic functional blocks: 1) the image-sensing area, 2) the advanced

lateral overflow drain (ALOD), 3) the storage area, 4) the serial register, and 5) the bulk charge detection (BCD)

node with the buffer output amplifier.

image-sensing area

The image-sensing area contains 1036 x 1010 pixel elements. A metal light shield covers 28 pixels on the left

edge of the sensing area, 8 pixels on the right edge, and 10 rows at the bottom of the sensing area. The dark

pixel signal can be used as a black reference during the video signal processing. The dark references will

accumulate the dark current at the same rate as the active photosites, thus representing the true black level

signal. As light enters the active photosites in the image area, electron hole pairs are generated and the

electrons are collected in the potential wells of the pixels. The wells have a finite charge storage capacity

determined by the pixel design. When the generated number of electrons in the illuminated pixels exceeds this

limit, the electrons could spill over into neighboring pixels and cause blooming. To prevent this problem, each

horizontal pair of pixels in the image sensing area shares a lateral overflow drain structure which provides up

to a 1000-to-1 protection against such undesirable phenomenon.

advanced lateral overflow drain

The advanced lateral overflow drain structure is shared by two neighboring pixels and provides several unique

features thus available in the sensor. By varying the dc bias of the drain pin, it is possible to control the blooming

protection level and trade it for the well capacity.

Applying a 10-V pulse for a minimum duration of 1 us above the nominal dc bias level causes charge in the image

area to be completely cleared. This feature permits a precise control of the integration time on a frame-by-frame

basis. The single-pulse clear capability also reduces smear by eliminating accumulated charge from the pixels

before the start of the integration (single sided smear).