Delay Locked Loop Modulation Driver with Optimal Current Spreading: an Enabler for Megapixel iToF Sensors

In this paper we suggest the mechanism of current spreading to suppress the modulation current peaks in a high resolution indirect-Time-of-Flight sensor. By dividing the pixel array into groups of columns that are driven by separate drivers, and by accurately controlling the time delay of each group, we demonstrate modulation current peak reduction by a factor of 4 and an almost complete removal of the transient behavior of the modulation current. The time delay between the slices is locked by a DLL, making it robust to temperature, process and supply voltage changes. The depth shift that is introduced to each slice by the DLL is removed during depth calculation by subtracting a constant phase shift from each slice. We show that by introducing this method we improve the pixel-to-pixel depth bias by a factor of 3 to under 3.5mm std, thus allowing the most demanding depth sensing applications to work without per-pixel bias correction, saving expensive system resources such as frame buffers, and improving the depth camera performance.