Monday, December 29, 2008

Patent: Aptina Gets Rid Of RST Wiring

Micron filed a patent application US20080291310 on 4T pixel with no global RST transistor wiring. The principle is quite self-explanatory from the picture below:

7 comments:

  1. Getting rid of the reset pin is a big step foward. I hear that the omnipixel 3-HS uses this kind of thing to improve light sensitivity, but I've never actually seen anything with those kind of OV pixels. Don't know of anybody else who has found a way around the reset problem.

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  2. Yes, RST routing elimination is a big deal. It's great to hear that Omnivision thinks in the same direction.

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  3. Maybe this is not only for the improvment of the light sensitivity. Eliminate RST routing provides a routing for GND line to connect substrate in each pixel for example ...

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  4. There is a payment for simplicity. Now that RST comes vertically they need to reset the entire pixel array to read a particular row. This looks like unnecessary power consumption. Performing RST once a frame may cause issues capturing an overexposed scene (assume A-nodes leak to gnd). One may also expect lower voltage range and higher PRNU through source follower capacitance reattached from RST to pix_out.

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  5. Perfoming RST once a frame is probably not an option in shared pixels. Power penalty might be not that big - even assuming 10nF array reseted every 10us to 3V we get just 3mA current.

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  6. This idea was already presented at the International Solid-State Circuits Conference. Does anyone know whether the idea is already used in products ?

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  7. Yes, it was presented on the conferences already. However, the patent application is broader than the conference papers, as it talks about few different implementations of this idea.

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