Average encoding scheme to reduce capacitive coupling effects in mixed-signal integrated circuits

In this paper, we present an encoding scheme, which we call the average encoding scheme, to compensate for the detrimental effects of capacitive coupling between digital metal layers that overlap analog metal layers in a mixed signal integrated circuit. The scheme is not limited for use in integrated circuits and can also be used on circuit boards. In general, a design that has limitations in the number of metal layers for shielding purposes can benefit from our average encoding technique. It does not need any additional bit lines and hence saves on expensive silicon real estate. We present an implementation of the average encoding scheme on the digital pixel sensor (DPS), with measured results. In certain scenarios, the encoding scheme can be adapted after the chip has been fabricated and can be tuned to the particular design. The encoding scheme has the characteristic of averaging and constraining the rate of change of charge accumulation due to coupling capacitance hence avoiding a charge build up on the analog metal lines.