UPDATE ON CLICPIX2 DESIGN Pierpaolo Valerio Edinei Santin

Pad geometry 2 25 um 2.5 um 3.5 um After a discussion with Sami, we worked on the pad shape We were recommended to leave a large enough opening for electroplating and have a spacing of 3 um from the opening to the edge of the pads Other restrictions are imposed by DRC rules and space for power distribution VDDA VSSA VDDD VSSD

Pad geometry 3 8 um 14 um 12 um 10 um 22.5 um There is only a 2 um spacing between the opening and the edge of the pad, but the opening is big enough for electroplating An added aluminium “tail” can increase the capacitance to a HVCMOS sensor

IR drops on VDDA/VSSA Ultra-thick metal, M6 (R sh ≈ 5 m Ω /sq), for power distribution With R u ≈ 36 m Ω, I px ≈ 10 µA, and N px = 128, we have ∆V ≈ 5.9 mV 4

Update on the readout scheme 5 The current readout architecture works as intended, but it’s difficult to use a fast clock due to synchronization issues In order to make it easier to design the DAQ board and firmware, we want to use a higher clock frequency with a clock recovery mechanism (8/10 bit encoding) Due to the lack of a PLL block, we will use the readout clock (100 MHz) as the input clock for control signals and have a second clock (≥ 640 MHz) only used for the readout command

Parallel Readout 6 In order to decouple the readout clock from the pixel clock, we can read more columns in parallel The picture depicts the case with one column at a time (as in CLICpix1)

Parallel Readout 7 If the chip is configured to read more than one column at a time, the pixel clock is divided by the number of columns being read out The data is then serialized with the readout clock 8/10 bit encoding can be added at the output

Readout Efficiency 8 If more than one column is being read out, all of them must finish shifting data at the same time This means that, due to the compression, the column with the most data (the slowest) limits the readout speed We can calculate the efficiency with various occupancies and number of parallel columns Occupancy Efficiency # columns

Readout Time 9 Occupancy Readout time (ms) # columns Occupancy Readout time (ms) # columns Readout time with a 640 Mb/s serializer Readout time with a 2 Gb/s serializer The readout time is well within the CLIC specifications even with 2 parallel columns

Other news 10 There is an joint Engineering run being prepared by RD53. It could be possible to submit our design in this run instead that in an MPW in order to have access to full wafers, which would greatly simplify the bump bonding process. Schedules and costs for this option are still not clear The bandgap(s) to be implemented are ready and their designer can modify the layout to have them fit CLICpix2 Better substrate isolation techniques were studied and will be implemented (specifically, using deep n- well to isolate the analog pixels from the digital logic)

Thank you! 11