Project Status and Action Items

K

kproc

Good job rotating the connectors. Delete CN1. I also want to move the Pico to the top of the board

flux

I’ll remove the extra CN1 connector and move the Pico module up toward the top edge of the PCB, then verify the placement.

flux

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.
K

kproc

I need a power switch and some output LEDs

flux

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.

flux

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
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Schematic

Layout

Preview

Schematic Execution Plan — Rackmount 12V Distribution PSU
Current Direction
Proceed with Rev A as a single-PSU, non-Ethernet, 12-slot-target distribution board plus LM5122 boost daughterboard interface. Use one validated slot/daughterboard channel first, then replicate after review.
Decisions Locked This Pass
  • Per-slot protection baseline: LM5069MMX-1/NOPB hot-swap controller with external N-channel MOSFET and current-sense resistor.
  • Why not integrated eFuse: JLC/Flux integrated eFuse candidates found were too low-current for ~16–20A continuous slot input.
  • Fault behavior: LM5069-1 latches off on fault; MCU can reset by cycling UVLO/enable. This is safer than blind auto-retry for high-current slots.
  • Edge connector: first-pass 32-pin pinout created in edge-connector-pinout-rev-a-daughterboard-slot.
  • Bellwether connector: PDFs are documented, but not importable EDA files. A custom component/footprint must be manually created from the Bellwether drawings or imported later from EDA library files.
Phase 1 — Custom Connector and Mechanical Baseline
  1. Manually create Bellwether 70012-1111 custom component and footprint using the supplied package and 2D drawings.
  2. Verify connector orientation, mounting holes, keying, and keepouts against the Dell D750E-S1 mechanical envelope.
  3. Create a rough board/chassis placement sketch before committing to 12 slots.
Phase 2 — One Distribution Slot Block
  1. Use LM5069MMX-1/NOPB as the first hot-swap controller candidate.
  2. Select external pass MOSFET(s), sense resistor, UVLO/OVLO divider, PWR resistor, TIMER capacitor, and PGD pull-up from the LM5069 datasheet/design calculator.
  3. Add one edge connector using the Rev A 32-pin pinout.
  4. Use 10 VIN and 10 GND contacts, interleaved where the physical connector permits.
  5. Drop AGND; use single GND and Kelvin/sense routing.
  6. Add EN, MODE, SYNC optional, FAULT, PGOOD, IIN, IOUT, TEMP_MOS, TEMP_IND, VOUT_SENSE, MOD_PRESENT, and SLOT_ID/SPARE.
Phase 3 — One Daughterboard Boost/Telemetry Block
  1. Wire the LM5122 boost stage from the user’s JLCPCB BoM after validating power-stage calculations.
  2. Add two INA181 current monitors: input-side 12V current and output-side 19.5V current.
  3. Add MOSFET and inductor thermistors.
  4. Add output voltage sense and hardware UVLO local to the daughterboard.
  5. Expose EN/MODE/FAULT/PGOOD/telemetry over the edge connector.
Phase 4 — MCU and Rev A Control
  1. Add Pico 2 / RP2350 controller and 3.3V logic power.
  2. Add USB/debug access.
  3. Add system status LED.
  4. Add enough ADC/mux/interface circuitry for the chosen analog telemetry strategy.
  5. Implement slot enable/fault handling for one slot first.
Phase 5 — Replication and Review
  1. Review the one-slot schematic electrically and mechanically.
  2. Replicate to 8, 10, or 12 slots depending on preliminary layout feasibility.
  3. Run ERC and power/thermal sanity checks.
  4. Pause before PCB layout routing until the slot count and physical arrangement are confirmed.
Immediate Decisions Still Needed
  • Exact external pass MOSFET arrangement for each LM5069 slot: single MOSFET vs parallel MOSFETs.
  • Sense resistor value and package/power rating for ~20A limit.
  • Final ED32BGFBK footprint/pin-numbering confirmation.
  • Whether analog telemetry goes directly to the distribution MCU or through daughterboard-local ADC/digital telemetry.
  • Whether barrel jacks mount directly on daughterboards or to the rear panel with wiring.

  • Current Direction

  • Decisions Locked This Pass

  • Phase 1 — Custom Connector and Mechanical Baseline

  • Phase 2 — One Distribution Slot Block

  • Phase 3 — One Daughterboard Boost/Telemetry Block

  • Phase 4 — MCU and Rev A Control

  • Phase 5 — Replication and Review

  • Immediate Decisions Still Needed