Texas Instruments TC254P Datasheet

TC254P

336- × 244-PIXEL CCD IMAGE SENSOR

SOCS060B – JUNE 1997 – REVISED JULY 1998

• Medium-Resolution, Solid-State Image

Sensor for Low-Cost Color TV Applications

• 324(H) x 243(V) Active Elements in Image

Sensing Area

• 10-µm Square Pixels

• Small Size

• Low Cost

• Fast Clear Capability

• Electronic Shutter Function From

1/60–1/50000 s

• Low Dark Current

• Electron-Hole Recombination Antiblooming

• Dynamic Range...66 dB Typical

• High Sensitivity

• High Blue Response

• 8-Pin Dual-In-Line Plastic Package

• 4-mm Image-Area Diagonal

• Solid-State Reliability With No Image

Burn-In, Residual Imaging, Image Distortion, Image Lag, or Microphonics

description

IAG2

ADB

SUB

OUT

DUAL-IN-LINE PACKAGE

(TOP VIEW)

ABG

IAG1

SAG

SRG

The TC254P is a frame-transfer charge-coupled device (CCD) designed for use in color NTSC TV and specialpurpose applications requiring low cost and small size.

The image-sensing area of the TC254P is configured in 243 lines with 336 elements in each line. Twelve elements are provided in each line for dark reference. The blooming-protection feature of the sensor is based on recombining excess charge with charge of opposite polarity in the substrate. This antiblooming is activated by supplying clocking pulses to the antiblooming gate, which is an integral part of each image-sensing element.

The sensor can be operated in a non-interlace mode as a 324(H) by 243(V) square color pixel mode by alternately averaging two red pixels for red pixels and two blue pixels for blue pixels. Because the human eye is most sensitive to the green light wavelength, the 324×243 resolution is preserved due to the orientation of the green pixels in the Bayer mosaic color filter pattern.

The device can also be operated in a 162(H) by 121(V) square color pixel mode by utilizing a separate red, two averaged greens, and a blue pixel for each color pixel. In this mode, true interlaced video is possible, effectively increasing the vertical resolution, by performing a one pixel shift during the off-chip video processing.

One important aspect of this image sensor is its high-speed image-transfer capability . This capability allows for an electronic shutter function comparable to interline-transfer and frame-interline-transfer sensors without the loss of sensitivity and resolution inherent in those technologies.

This MOS device contains limited built-in gate protection. During storage or handling, the device leads should be shorted together or the device should be placed in conductive foam. In a circuit, unused inputs should always be connected to SUB. Under no circumstances should pin voltages exceed absolute maximum ratings. Avoid shorting OUTn to ADB during operation to prevent

allowed to flow. Specific guidelines for handling devices of this type are contained in the publication

Electrostatic-Discharge-Sensitive (ESDS) Devices and Assemblies

damage to the amplifier. The device can also be damaged if the output terminals are reverse-biased and an excessive current is

Guidelines for Handling

available from Texas Instruments.

PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

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TC254P 336- × 244-PIXEL CCD IMAGE SENSOR

SOCS060B – JUNE 1997 – REVISED JULY 1998

description (continued)

Charge is converted to signal voltage with a 12-µV per electron conversion factor by a high-performance charge-detection structure with built-in automatic reset and a voltage reference generator. The signal is buf fered by a low-noise two-stage source-follower amplifier to provide high output-drive capability.

The TC254P is built using TI-proprietary virtual-phase technology, which provides devices with high blue response, low dark current, high photoresponse uniformity, and single-phase clocking. The TC254P is characterized for operation from –10°C to 45°C.

functional block diagram

IAG2

ADB

OUT

SUB

Image Area With

Blooming Protection

2 Dummy Elements

Amplifier

Dark Reference Elements

Clear Line

Storage Area

Serial Register

Clearing Drain

ABG

IAG1

SAG

SRG

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sensor topology diagram

I/O

DESCRIPTION

336- × 244-PIXEL CCD IMAGE SENSOR

123456 323324

Pixel

R G R G R G R G G B G B G B G B R G R G R G R G G B G B G B G B

TC254P

SOCS060B – JUNE 1997 – REVISED JULY 1998

Line 243 Line 242 Line 241 Line 240

243 Lines

244 Lines

12 OB

R G R G R G R G G B G B G B G B R G R G R G R G G B G B G B G B

1 Dark Line 1Clear Line

Storage Area

Buffer Column

Line 4 Line 3 Line 2 Line 1

OB = Optical Black R = Red B = Blue G = Green

336 Pixels

123456

12 OB R G

323 324

Terminal Functions

TERMINAL

NAME NO.

ABG 8 I Antiblooming gate ADB 2 I Supply voltage for amplifier-drain bias SUB 3 Substrate IAG1 7 I Image-area gate 1 IAG2 1 I Image-area gate 2 OUT 4 O Output SAG 6 I Storage-area gate SRG 5 I Serial-register gate

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

SRG

TC254P 336- × 244-PIXEL CCD IMAGE SENSOR

SOCS060B – JUNE 1997 – REVISED JULY 1998

detailed description

The TC254P consists of five basic functional blocks: (1) the image-sensing area, (2) the image-clear line, (3) the storage area, (4) the serial register, and (5) the charge-detection node and output amplifier.

image-sensing area

Cross sections with potential well diagrams and top views of image-sensing and storage-area elements are shown in Figure 1 and Figure 2. As light enters the silicon in the image-sensing area, free electrons are generated and collected in the potential wells of the sensing elements. During this time, the antiblooming gate is activated by the application of a burst of pulses every horizontal blanking interval. This prevents blooming caused by the spilling of charge from overexposed elements into neighboring elements. Twelve columns of shielded-from-light elements on the left edge of the image-sensing area generate the dark reference necessary in subsequent video processing circuits for restoration of the video-black level. There is also one column of elements on the right side of the image-sensing area and one line between the image-sensing area and the image-clearing line.

10 µm

Clocked Barrier

Virtual Barrier Antiblooming Gate

Virtual Well

Clocked Well

Antiblooming

Clocking Levels

Accumulated Charge

Figure 1. Charge-Accumulation Process

SAG

Clocked Phase

Virtual Phase

IAG

Light

ABG

Channel Stops

Figure 2. Charge-Transfer Process

image-clear line

During start-up or electronic-shutter operations, it is necessary to clear the image area of charge without transferring it to the storage area. In such situations, the two-image area gates are clocked 244 times without clocking the storage-area gate. The charge in the image area is then cleared through the image-clear line.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

336- × 244-PIXEL CCD IMAGE SENSOR

SOCS060B – JUNE 1997 – REVISED JULY 1998

storage area

After exposure, the charge captured in each image-area is transferred through the image clear line to the storage area. The stored charge is then transferred line by line into the serial register for readout. Figure 3 illustrates the timing to (1) transfer the image to the storage area, and (2) to transfer each line from the storage area to the serial register.

serial register

Each line, after it is clocked into the serial register, is read out pixel by pixel. Figure 3 illustrates the serial-register clock sequence.

244 Cycles

Composite

Blank

Integration Time

ABG

Electronic

Shutter

Operation

244 Clocks

TC254P

IAG1

IAG2

SAG

SRG

SAG

1) 2) 3)

SRG

1) End of serial readout of line

2) Transfer of new line to serial register

3) Beginning of readout of new line

339 Cycles

t = 80 ns

IAG1

IAG2

SAG

SRG

Figure 3. Timing Diagram

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Expanded Section of Parallel Transfer

+ 11 hidden pages