V5: Wrong impedance on diff pairs in L3 and L4
During the production of V4.1 (later renamed to V5 in order to fix minor non-comformities and update licence to OHL-W v2) the CERN design office spotted several diff pairs in layers 3 and 4 having the wrong impedance (see EDA-02541-V5_stackup.pdf).
These pairs include:
- layer L3:
SFP_CLK
MGT_SFP_RX0
MGT_SFP_TX0
FPGA_MGT_CLK0
FPGA_CLK
- layer L4:
RS485_L_1/2/3/4/5/6
RS485_C_1/2/3/4/5/6
RS485_R_1/2/3/4/5/6
Calculated diff impedance is around 87Ω when it should be 100Ω.
It was decided to leave them as is since there's several of these boards operating fine and fix them next time we revisit the board and need to do a design change.