Project Status and Action Items
Worked for 1 min 27 sec
Done. I deleted
CN1 and moved U_MCU/Pico to the top of the board; it is now centered at about (10 mm, 88 mm) with its top edge just inside the board outline.Open item: the Pico was clamped at the board edge, so if you want more clearance from the top edge I can drop it slightly lower.
I need a power switch and some output LEDs
Thought for 5 sec
I’ll add a low-current front-panel power/enable switch rather than a high-current 12 V path switch, plus output/status LEDs with current-limiting resistors, then verify the schematic changes.
Worked for 1 min 54 sec
Added the power switch and output LEDs.
SW_PWR is a low-current front-panel switch that pulls Pico 3V3_EN to GND to turn logic off, and I added green indicators for BUS_12V and VOUT_19V5 with 4.7kΩ and 8.2kΩ series resistors.Open items:
- These are placed near the top/front-panel area but not routed yet.
- If you intended a true high-current input disconnect instead of a Pico enable switch, that needs a different switch/contactor architecture.
Route controls and verify
Use high-current switch
Route switch and LEDs
Add LED labels
Run design review
Refine this doc
Ask about this doc
Layout Split and Edge-Finger Plan
Decision
Use 4-layer PCBs and treat the design as two physical boards:
- Distribution Board — rack backplane / power distribution PCB.
- 19.5 V / 180 W Boost Daughterboard — repeated plug-in module using PCB edge fingers.
The current Flux project schematic intentionally contains one representative slot and one representative daughterboard block, but layout should not be finalized as one monolithic PCB.
Daughterboard Project
- New project created: 19.5V 180W Boost Daughterboard
- Purpose: hold the standalone LM5122 boost-module schematic, edge-finger PCB outline, 4-layer stackup, and daughterboard-specific placement/routing.
- Parent distribution project should retain only the distribution board/backplane circuitry plus a representative slot connector interface.
Current Layout State
- Current distribution-board outline: 157.5 mm × 230 mm rectangle.
- Current stackup: Standard 4 Layer.
- Boost-module circuitry has been moved out of the parent layout conceptually; the parent project is now distribution-board/backplane focused.
- Physical slot connector placement uses the user's published ED32BGFBK part.
Distribution Board Layout Intent
- Function: PSU input, upstream LM5069 hot-swap stage, high-current 12 V bus, Pico control plane, PMBus, status LED, and 12 slot receptacles.
- Board likely runs alongside the PSU bay inside the 10 inch / 2U chassis.
- Slot connectors run front-to-back.
- Use heavy copper pours/busbar strategy for BUS_12V and GND; standard traces are not appropriate for 100–150 A.
- Place upstream hot-swap MOSFET bank and Kelvin shunt close to the HPSU input connector with a short, wide current path and clear airflow.
- Pico/control circuitry should sit away from the high-current MOSFET/shunt heat source.
Daughterboard Layout Intent
- Function: one 12 V input to 19.5 V / up to 10 A output boost module.
- Requires PCB edge fingers mating into the distribution-board ED32BGFBK receptacle.
- DC barrel output jack sits at the rear/exposed edge.
- Board target height usage: about 50 mm within the 2U chassis, excluding edge-finger engagement and mechanical clearance.
- LM5122 controller, VCC/BOOT/COMP/RT/SS passives must be close to U1.
- Power MOSFETs, inductor, input caps, output caps, shunts, and sense routing need a compact boost power-stage layout.
- Keep high di/dt loop areas small; prioritize hot-loop layout over aesthetic placement.
- Use inner GND plane and large copper pours for thermal/current spreading.
Edge Finger Requirements To Finalize
Before fabrication, define and verify:
- Finger count and exact pin numbering against ED32BGFBK mating connector.
- Finger pitch, width, gap, insertion depth, and board thickness.
- ENIG/hard-gold requirement and gold thickness.
- Soldermask pullback around fingers.
- Bevel angle/depth for insertion.
- Mechanical keepout and card guide / retention method.
- Whether VIN/GND fingers need staggered lengths for controlled sequencing.
Recommended Next CAD Step
Use this project as the distribution board/backplane project, and use the daughterboard project for the edge-finger boost-module PCB. Do not route both physical boards as one PCB.
Distribution Board Placement Plan
- Place Bellwether/Dell HPSU input connector at the rear PSU interface location once the custom footprint is complete.
- Place LM5069 hot-swap controller near the input connector, but thermally separated from the pass MOSFET bank.
- Place 6× hot-swap MOSFETs and the Kelvin shunt in a short, straight high-current path from PSU input to BUS_12V copper/busbar region.
- Place bulk input capacitance close to the protected BUS_12V side, respecting inrush/LM5069 SOA calculations.
- Place Pico/control logic away from hot MOSFETs and shunt; route PMBus/control as low-current signals with GND reference.
- Place 12 ED32BGFBK slot receptacles front-to-back in the module bay on 12 mm center-to-center spacing.
- Keep 12 V and GND distribution as planes/pours/busbar-style copper; do not rely on narrow traces for slot current.
Current Slot Connector Placement
- Slot connector part: ED32BGFBK, user published part UID
4158ffae-7548-4b4c-aa8b-ff75fecc94f9. - Designators:
J_SLOT1throughJ_SLOT12. - Placement pitch: 12 mm center-to-center.
- Current centers: X = -66, -54, -42, -30, -18, -6, +6, +18, +30, +42, +54, +66 mm; Y = -70 mm.
- Orientation: rotated 90° so the connector row is intended to run front-to-back.
- Caveat: the current ED32BGFBK part is still footprint-only / not electrically terminal-mapped, so it can be placed mechanically but cannot yet replace the schematic pinout wiring.
Daughterboard Placement Plan
- Put edge fingers on the distribution-board mating edge with finalized bevel, plating, soldermask pullback, and insertion depth.
- Put the module-side fuse immediately after VIN entry from edge fingers.
- Keep input capacitors, inductor, MOSFETs, current shunt, and LM5122 gate-drive loop extremely compact.
- Put LM5122 and compensation/timing/support components close together, away from the hottest MOSFET/inductor copper if practical.
- Place output capacitors, output shunt, TVS, and barrel jack at the rear output edge.
- Place thermistors next to the MOSFET hot spot and inductor hot spot, not merely near the controller.
Decision
Daughterboard Project
Current Layout State
Distribution Board Layout Intent
Daughterboard Layout Intent
Edge Finger Requirements To Finalize
Recommended Next CAD Step
Distribution Board Placement Plan
Current Slot Connector Placement
Daughterboard Placement Plan
