TC285SPD-B0 Datasheet, PDF (7/30 Pages) Texas Instruments – 1004 x 1002 PIXEL IMPACTRONTM CCD IMAGE SENSOR

TC285SPD-B0
1004 x 1002 PIXEL IMPACTRON^TM CCD IMAGE SENSOR
SOCS093 – JANUARY 2006
Advanced lateral overflow drain
The advanced lateral overflow drain structure is shared by two neighboring pixels in each
line. By varying the DC bias of the anti-blooming drain it is possible to control the
blooming protection level and trade it for well capacity. Applying a pulse to the drain,
approximately 6V above the nominal level, for a minimum of 100µs(3H), removes all
charge from the pixels. This feature permits precise control of the integration time on a
frame-by-frame basis. The single-pulse clearing capability also reduces smear by
eliminating accumulated charge in pixels before the start of the integration period (single
sided smear).
Serial register and charge multiplier
The serial register of TC285SPD image sensor consists of only poly-silicon gates. It
operates at high speed, being clocked from 0V to 8V. This allows the sensor to work at
30 frames/s. The serial register is used for transporting charge stored in the pixels of the
memory lines to the output amplifier. The TC285SPD device has a serial register with
twice the standard length. The first half has a conventional design that interfaces with the
memory as it would in any other CCD sensor. The second half, however, is unique and
includes 400 charge multiplication stages with a number of dummy pixels that are needed
to transport charge between the active register blocks and the output amplifier. Charge is
multiplied as it progresses from stage to stage in the multiplier toward the charge
detection node. The charge multiplication level depends on the amplitude of the
multiplication pulses (approximately 15V~22V) applied to the multiplication gate. Due to
the double length of the register, first 2 lines in each field or frame scan do not contain
valid data and should be discarded.
Charge detection node and buffer amplifier
The last element of the charge detection and readout chain is the charge detection node
with the buffer amplifier. The charge detection node is using a standard Floating
Diffusion (FD) concept followed by an on-chip dual-stage source-follower buffer.
Another bipolar transistor (third stage) has been included in the sensor package to
improve the driving capability at high speed. A load for the bipolar transistor (2.2kOhm)
needs to be connected externally from the package output pin to SUB. Applying a pulse
to the RST pin resets the detection node. Pixel charge summing function can be easily
implemented by skipping the RST pulses. To achieve the ultimate sensor performance it
is necessary to eliminate kTC noise. This is typically accomplished by using CDS
(correlated double sampling) processing techniques. IMPACTRON^TM devices have the
potential for detecting single electrons (photons) when cooled or when sufficiently short
integration times are used.
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