CCD143A Datasheet, PDF (2/12 Pages) List of Unclassifed Manufacturers – 2048-Element High Speed Linear Image Sensor

CCD143
2048-Element High Speed Linear Image Sensor
FUNCTIONAL DESCRIPTION
The CCD143 consists of the following functional elements illustrated
in the Block Diagram:
Image Sensor Elements — These are elements of a line of
2048 image sensors separated by diffused channel stops and
covered by a silicon dioxide surface passivation layer. Image
photons pass through the transparent silicon dioxide layer and are
absorbed in the single crystal silicon creating hole-electron pairs.
The photon generated electrons are accumulated in the photosites.
The amount of charge accumulated 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 noise background at zero illumination to a
maximum at saturation under bright illumination.
Transfer Gates — This gate is a structure adjacent to the line of
image sensor elements. The charge packets accumulated in the
image sensor elements are transferred out via the transfer gate to
the transport registers whenever the transfer gate goes HIGH.
Alternate charge-packets are transferred to the analog transport shift
registers. The transfer gate also controls the exposure time for the
sensing elements.
Four 1041-Bit Analog Transport Shift Registers — Two
registers are on each side of the line of image sensor elements and
are separated from it by the transfer gate. The two inside registers,
called the transport shift registers, are used to move the image
generated charge packets delivered by the transfer gates serially to
the two charge-detector/amplifiers. The complementary phase
relationship of the last elements of the two transport registers
provides for alternate delivery of charge-packets to the amplifiers so
that the original serial sequence of the line of video may be
reestablished at the outputs. The outer two registers serve to reduce
peripheral electron noise in the inner shift registers.
Two Gated Charge-Detector/Amplifiers — From the end of
each transport shift register, charge-packets are delivered to a
precharge diode whose potential changes linearly in response to the
quantity of the signal charge delivered. This potential is applied to
the gate of an n-channel MOS transistor producing a signal which
passes through the sample-and-hold gate to the output at “Videou t”.
The sample-and-hold gate is a switching MOS transistor in the
output amplifier that allows the output to be delivered as a sample-
and-hold waveform. The diode is recharged internally before the
arrival of each new signal charge-packet from the transport shift
register.
Clock Driver Circuitry — This circuitry allows operation of the
CCD143A using only two external clocks, (1) a square wave
transport clock which controls the readout rate of video data from the
sensor, and (2) a transfer clock pulse which controls the integration
time of the sensor.
Dark and Optional White Reference Circuitry — Four
additional sensing elements at both ends of the 2048 array are
covered by opaque metallization. They provide a dark (no
illumination) signal reference which is delivered at both ends of the
line of video output representing the 2048 illuminated sensor
elements (labeled “D” in the Block Diagram). Also included at one
end of the 2048 sensor element array is a white signal reference in
the output signal (labeled “W” in the Block Diagram). These
reference levels are useful as inputs to external dc restoration and
automatic gain control circuitry. The white reference signal can be
enabled by connecting VEI to a DC voltage less than VD D . A VE I
voltage of 6V will typically produce a white reference signal of
80=20% of the saturation output voltage.
DEFINITION OF TERMS
Charge-Coupled Device — A charge-coupled device is a
semiconductor device in which finite isolated charge-packets are
transported from one position in the semiconductor to an adjacent
position by sequential clocking of an array of gates. The charge-
packets are minority carriers with respect to the semiconductor
substrate.
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