Sony Presents GS Sensor with ADC per Pixel

Sony presents 1.46MP stacked BSI CMOS sensor with Global Shutter and newly developed low power pixel-parallel ADC to convert the analog signal from all pixels, simultaneously exposed, to a digital signal in parallel.

The inclusion of nearly 1,000 times as many ADCs compared to the traditional column-parallel ADC architecture means an increased demand for current. Sony addressed this issue by developing a compact 14-bit A/D converter which is said to boast the industry's best performance in low-current operation. The FoM of the new ADC is 0.24e-・nJ/step. (power consumption x noise) / {no. of pixels x frame speed x 2^(ADC resolution)}.

The connection between each pixel on the top chip uses Cu-Cu connection, that Sony put into mass production as a world-first in January 2016.

Main Features:

Low-current, compact pixel-parallel A/D converter
In order to curtail power consumption, the new converter uses comparators that operate with subthreshold currents, resulting in the low current, compact 14-bit ADC. This overcomes the issue of the increased demand for current due to the inclusion of nearly 1,000 times as many ADCs in comparison with the traditional column ADC.
Cu-Cu (copper-copper) connection
To achieve the parallel A/D conversion for all pixels, Sony has developed a technology which makes it possible to include approximately three million Cu-Cu (copper-copper) connections in one sensor. The Cu-Cu connection provides electrical continuity between the pixel and logic substrate, while securing space for implementing as many as 1.46 million A/D converters, the same number as the effective megapixels, as well as the digital memory.
High-speed data transfer construction
Sony has developed a new readout circuit to support the massively parallel digital signal transfer required in the A/D conversion process using 1.46 million A/D converters, making it possible to read and write all the pixel signals at high speed.