Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500

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CCD181

GENERAL DESCRIPTION

The CCD181 is a 2592-element line image sensor designed for

industrial measurement, telecine, and document scanning

applications which require high resolution, high sensitivity and high

data rate. Incorporation of on-chip anti-blooming and integration

controls allow the CCD181 to be extremely useful in an industrial

measurement and control environment or in environments where

lighting conditions are difficult to control.

The CCD181 is equipped with special gates which allow the user

to select 4 effective array lengths:

2592 elements: 300-lines/inch across 8.5 inch wide document

2048 elements: 240-lines/inch across 8.5 inch wide document

1728 elements: 200-lines/inch across 8.5 inch wide document

1024 elements: 120-lines/inch across 8.5 inch wide document

The CCD181 is a third generation device having an overall improved

performance compared with first and second generation devices,

including enhanced blue response and excellent low light level per-

formance, and high-speed operation up to 20 MHz.

The photoelement size is 10

µm (0.39 mils) x 10µm (0.39 mils) on

10

µm (0.39 mils) centers. The device is manufactured using Fairchild

Imaging’s advanced charge-coupled device n-channel isoplanar

buried-channel technology.

FUNCTIONAL DESCRIPTION

The CCD191 consists of the following functional elements illustrated

in the Block Diagram and Circuit Diagram (see Fig. 1A).

a diffused channel stop and covered by a silicon dioxide surface

passivation layer. Image photons pass through the transparent sili-

con creating hole-electron pairs. The photon generated electrons

are accumulated in the photosites. The amount of charge accumu-

lated in each photosite is a linear function of the incident illumination

intensity and the integration period. The output signal will vary in an

analog manner from a thermally generated background level at zero

illumination to a maximum at saturation under bright illumination.

age sensor elements. The charge packets accumulated in the

photosites are transferred in parallel via the transfer gates (

transport shift registers whenever the transfer gate voltages go high.

Alternate charge packets are transferred to the A and B transport

registers.

used to move the light generated charge packets delivered by the

transfer gates. (

plifier. The complementary phase relationship of the last elements of

the two transport registers provides for alternate delivery of charge

packets at the output amplifiers.

transported to a precharge capacitor whose potential changes lin-

early in response to the quantity of the signal charge delivered. This

potential is applied to the input gate of the two-stage NMOS amplifi-

packet is sensed, a reset clock (

tions the dynamic range in parts of the image is larger than the dy-

namic range of the CCD, which may cause more electrons to be

generated in the photosite area than can be stored in the CCD shift

register. This is particularly common in industrial inspection and sat-

ellite applications. The excess electrons generated by bright illumi-

nation tend to “bloom” or “spill over” to neighboring pixels along the

shift register, thus “smearing” the information. This smearing can be

eliminated using two methods:

Anti-Blooming Operation:

A DC voltage applied to the integration control gate (approximately 5

to 7 volts) will cause excess charge generated in the photosites to be

ters. This acts as a “clipping circuit” for the CCD output. (see Fig. 2)