Project Status and Action Items

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.
kproc

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 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

Rackmount 12V Distribution PSU

Rackmount 12V Distribution PSU thumbnail
2U 10-inch rackmount 12V distribution power supply for Dell server PSUs, with 12 managed boost-module slots, per-slot current monitoring, temperature logging, MCU supervision, and optional Ethernet metrics.

Properties

Ethernet

Power Electronics

JLCPCB assembly target

High Current

12

V

Pricing & Availability

Distributor

Qty 1

Arrow

$5.24–$8.55

Digi-Key

$4.74–$5.13

HQonline

$1.68–$1.79

LCSC

$16.68–$17.00

Mouser

$11.43–$11.83

TME

$10.48–$10.77

Verical

$4.88–$14.99

Controls