RGBZ pixel cell unit for an RGBZ image sensor

A computing system, comprising:

• an applications processor having multiple processing cores coupled to a memory controller, said memory controller coupled to a system memory;
• a camera system coupled to said applications processor, said camera system comprising an image sensor, said image sensor comprising a pixel array having a unit cell that includes visible light photodiodes and an infra-red photodiode, the visible light photodiodes and the infra-red photodiode coupled to a particular column of the pixel array, the unit cell having a first capacitor coupled to the visible light photodiodes to store charge from each of the visible-light photodiodes, the unit cell having a readout circuit to provide the first capacitor's voltage on the particular column, the unit cell having a second capacitor that is coupled to the infra-red photodiode through a transfer gate transistor to receive charge from the infra-red photodiode during a time-of-flight exposure, the unit cell comprising a back-drain transistor coupled to the infra-red photodiode.