TC237B Datasheet, PDF (3/15 Pages) Texas Instruments – 680-×500-PIXEL CCD IMAGE SENSOR

TC237B
680- × 500-PIXEL CCD IMAGE SENSOR
TERMINAL
NAME NO.
ADB
4
IAG1
12
IAG2
2
ODB
1
OUT1
5
OUT2
6
RST
7
SAG
10, 11
SRG
8
SUB
3, 9
Terminal Functions
I/O
DESCRIPTION
I
Supply voltage for amplifier drain bias
I
Image area gate 1
I
Image area gate 2
I
Supply voltage for drain antiblooming bias
O Output signal 1
O Output signal 2
I
Reset gate
I
Storage area gate
I
Serial register gate
Substrate
SOCS063 – APRIL 2001
detailed description
The TC237B CCD image sensor 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 image storage areas
Figure 1 and Figure 2 show cross sections with potential well diagrams and top views of the image-sensing and
storage area elements. As light enters the silicon in the image-sensing area, electrons are generated and
collected in the wells of the sensing elements. Blooming protection is provided by applying a dc bias to the
overflow drain bias pin. To clear the image before beginning a new integration time (for implementation of
electronic fixed shutter or electronic auto-iris), apply a pulse of at least 1 µs to the overflow drain bias. After
integration is complete, charge voltage is transferred into the storage area. The transfer timing depends on
whether the readout mode is interlace or progressive scan. If the progressive-scan readout mode is selected,
the readout may be performed by using one serial register or at high speed by using both serial registers (see
Figure 3 through Figure 5). A line-summing operation, which is useful in off-chip smear subtraction, can be
implemented before the parallel transfer (see Figure 6).
Twenty-two columns at the left edge of the image-sensing area are shielded from incident light; these elements
provide the dark reference used in subsequent video-processing circuits to restore the video black level. In
addition, four dark lines between the image-sensing and the image storage area prevent charge leakage from
the image-sensing area into the image storage area.
advanced lateral overflow drain
The advanced lateral overflow drain structure is shared by two neighboring pixels and provides several unique
features in the sensor. By varying the dc bias of the drain pin, you can control the blooming protection level and
trade it for the well capacity.
To clear charge voltages in the image area, apply a 10-V pulse for a minimum duration of 1 µs above the nominal
dc bias level. 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).
Application of a negative 1-V pulse to the ODB signal during the parallel transfer is recommended to prevent
slight column-to-column pixel well capacity variations in some artifacts.
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