Description of the Differential Pair Via Geometries ---------------------------------- Original Rev. 27-Aug-2016 Current Rev. 14-Feb-2017 There are a number of Differential Pair Geometry Components used in the Hub Module design. These are full Mentor components with through hole pins. They are in the net list files. The Differential Pair Geometries typicall include a return current Ground pin or pins. These components are used to implement routing layer changes of high-speed and differential clock signals. The difference between one of these geometries and the next is typically in the number and spacing of the associated Ground return pins. This files is a description of the various Differential Pair Via Geometries that are used in the Hub Module. Each geometry source file is listed by its file name and then by the name of the geometry or geometries included in that file. File: diff_pair_through Geometry: DIFF_PAIR_THRU This is a 4 pin component: pins 1 and 4 are Ground pins 2 and 3 are the Diff Pair Spacing between pins is: 1.00 mm between Diff Pair 1.20 mm Diff Pair to Gnd <--- This geometry has a Ground Plane Cutout on PREPREG_3 The origin point of this geometry is its geometric center, i.e. half-way between pins #2 and #3. This geometry has nothing visible on the Silkscreen. This geometry is excluded from the Bill of Materials. This source file includes the Pin/Pad Stack deffinitions for all of the Differential Pair Geometries: DIFF_PAIR_THRU_SIG_PAD 0.25 mm finished hole diameter 0.52 mm land pad 1.00 mm plane relief 0.46 mm soldermask opening, i.e. not tented --> ring width 0.135 mm --> plane isolation Air Gap 0.240 mm from the pad --> plane isolation Air Gap 0.375 mm from edge of drill hole DIFF_PAIR_THRU_GND_PAD 0.30 mm finished hole diameter 0.60 mm land pad 0.87 mm plane relief 0.55 mm soldermask opening --> ring width 0.150 mm --> plane isolation Air Gap 0.135 mm from the pad --> plane isolation Air Gap 0.285 mm from edge of drill hole But Note: The plan is to bury aka flood these Ground Vias into the Hub's Ground Planes and the clearance between these vias and the Fills is controlled by the Fill-Pad or Fill-Pin design rule that is in effect when the fills are generated. Thus the "plane releif" specification, although needed in the deffinition of these pin/pad stacks, is not actually used in the Hub Design. File: diff_pair_thru_1g Geometry: DIFF_PAIR_THRU_1G This is a 1 pin component: pin 1 is a Ground This geometry has nothing visible on the Silkscreen. This geometry is excluded from the Bill of Materials. The purpose of this geometry is to complete a series of Diff Pair Via Components that include just one Ground pin between the differential pair vias, e.g. G S S G S S G S S G ------- ------- ------- - File: diff_pair_thru_1mm Geometry: DIFF_PAIR_THRU_1MM This is a 4 pin component: pins 1 and 4 are Ground pins 2 and 3 are the Diff Pair Spacing between pins is: 1.00 mm between Diff Pair 1.00 mm Diff Pair to Gnd <--- This geometry has a Ground Plane Cutout on PREPREG_3 The origin point of this geometry is its geometric center, i.e. half-way between pins #2 and #3. This geometry has nothing visible on the Silkscreen. This geometry is excluded from the Bill of Materials. This geometry is exactly like DIFF_PAIR_THRU except that the Ground Vias are spaced 1.00 mm from the adjacent differential signal via (instead of 1.20 mm). File: diff_pair_thru_3p Geometry: DIFF_PAIR_THRU_3P This is a 3 pin component: pin 1 is a Ground pins 2 and 3 are the Diff Pair Spacing between pins is: 1.00 mm between Diff Pair 1.00 mm Diff Pair to Gnd <--- This geometry has a Ground Plane Cutout on PREPREG_3 The origin point of this geometry is half-way between pins #2 and #3, i.e. the differential signal pins. This geometry has nothing visible on the Silkscreen. This geometry is excluded from the Bill of Materials. This geometry is exactly like DIFF_PAIR_THRU_1MM except that the Ground Pin #4 is not included. This geometry is used along with DIFF_PAIR_THRU_1G to make a series of differential pair connections that include just one Ground pin between them. File: diff_pair_thru_3p_1mm1 Geometry: DIFF_PAIR_THRU_3P_1MM1 This is a 3 pin component: pin 1 is a Ground pins 2 and 3 are the Diff Pair Spacing between pins is: 1.00 mm between Diff Pair 1.10 mm Diff Pair to Gnd <--- This geometry has a Ground Plane Cutout on PREPREG_3 The origin point of this geometry is half-way between pins #2 and #3, i.e. the differential signal pins. This geometry has nothing visible on the Silkscreen. This geometry is excluded from the Bill of Materials. This geometry is exactly like DIFF_PAIR_THRU_3P except that the the spacing between its single Ground pin and the adjacent differential signal pin is 1.10 mm (instead of 1.00 mm). Files: diff_pair_thru_3p_top_mid_relief Geom: DIFF_PAIR_THRU_3P_TOP_MID_RELIEF diff_pair_thru_3p_mid_bot_relief Geom: DIFF_PAIR_THRU_3P_MID_BOT_RELIEF These two geometries are similar to the DIFF_PAIR_THRU_3P geometry but they are setup so that you can have for example full oval ground plane releif on the Top & Mid Ground Planes with a two circle ground plane relief on the Bottom Ground Plane. The diff_pair_thru_3p_top_mid_relief geometry uses the layer "GLUE_MASK_1" (along with POWER) to indicate where the Ground Planes should be releived. The diff_pair_thru_3p_mid_bot_relief geometry uses the layer "COMPONENT_METAL_1" (along with POWER) to indicate where it needs the Ground Planes should be releived.