The IIS Chip Gallery
Corint (1995)
by
| Application | Graphics |
| Technology | 1200 |
| Manufacturer | VLSI Tech |
| Type | Semester Thesis |
| Package | PGA100 |
| Dimensions | 5170μm x 5200μm |
| Gates | 16 kGE |
| Voltage | 5 V |
| Power | 2.8W (5V, 118MHz) mW |
| Clock | 118 MHz |
CORINT is a chip that is able to compensate for the non-idealities of a CCD sensor on a per pixel basis. In addition, it is also able to calculate true color values through interpolation. The two non-idealities that can be corrected by CORINT are, dark current and white balance mismatch.
CCD image sensors suffer from two main sources of error: dark current due to charge leakage, and " white field imbalance due to gain differences of the individual pixels. The correction stage of the de signed chip uses 16 bits of correction data per pixel which is stored in external EDRAM chips: 6 bits for offset and 10 bits for gain adjustment. The ASIC uses the 8 on-chip SRAM caches of the EDRAMs to implement a time-multiplexed scheme for efficiently accessing 32 bits of correction data over a single 16 bit data port, which is necessary since two pixels arrive in parallel from the sensor. Gray unit-distance address counters minimize the amount of off-chip address pin toggles, reducing power consumption and noise.
In a second processing stage the color-sub-sampled image from the sensor is reconstructed using a memory-less algorithm working on the two scan lines coming simultaneously from the sensor. This scheme us foregoes the need for large on-chip line memories.
The fabricated ASIC contains 68000 transistors. It was successfully tested with a fault coverage of 99% and functioned up to 118MHz clock frequency (specified maximum operating frequency: 77MHz).
CORINT was developed for a digital endoscopy system where the correct reproduction of the image colors is important. However, it can be used with any application that uses the Kodak CCD sensor of the type KAI-1001. At the the time of the design, Kodak was offering four variants of the sensor (color, black, with and without microlens) and CORINT can be used with any of these four versions.
Matthias later joined the The microelectronics design center at the ETH, where he was instrumental in developing the design flows that are still being used today.