SOCS057 - JUNE 1996
The TC255P is a frame-transfer charge-coupled device (CCD) designed for use in B/W NTSC TV and special- purpose applications where low cost and small size are desired.
The image-sensing area of the TC255P 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 noninterlace mode as a 324(H) by 243(V) sensor with very low dark current. The device can also be operated in an interlace mode, electronically displacing the image-sensing elements during the charge integration in alternate fields, effectively increasing the vertical resolution and minimizing aliasing.
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.
The charge is converted to signal voltage with a 12-uV per electron conversion factor by a high-performance charge-detection structure with built-in automatic reset and a voltage reference generator. The signal is buffered by a low-noise two-stage source-follower amplifier to provide high output-drive capability.
The TC255P is built using TI-proprietary virtual-phase technology, which provides devices with high blue response, low dark signal, good uniformity, and single-phase clocking. The TC255P is characterized for operation from -10°C to 45°C.
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 damage to the amplifier. The device can also be damaged if the output terminals are reverse-biased and an excessive current is allowed to flow. Specific guidelines for handling devices of this type are contained in the publication Guidelines for Handling Electrostatic-Discharge-Sensitive (ESDS) Devices and Assemblies available from Texas Instruments.
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