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
Distribution Board BoM Review — Rackmount 12V Distribution PSU
Status
Draft review of the user-supplied distribution-board BoM and 32-pin daughterboard edge-connector allocation. JLCPCB assembly compatibility is a preferred constraint, but high-current safety and thermal margin take priority.
Supplied Distribution Board BoM
Power Input & Protection
- F1: TI TPS259827ONRGET, C2155765, hot-swap/eFuse controller, Flux library match found, JLCPCB Extended Part.
- D2: Littelfuse SMBJ15A, C83846, 12V input TVS candidate.
- C1-C2: Ymin VKMJ2101E472MV, C487341, electrolytic bulk capacitors.
- C3-C4: Ymin NPLC1101C471MJTM, C20539442, polymer bulk capacitors.
- C5-C10: Samsung CL31A106KAHNNNE, C9807, 10uF MLCC bank.
- C11-C16: YAGEO CC0603KRX7R9BB104, C14663, 100nF MLCC bank.
PSU Control & Sensing
- U1: Raspberry Pi Pico 2, C41407547.
- U3: TI INA3221AIRGVR, C181255, Flux library match found, JLCPCB Extended Part.
- R1-R4: 4.7kΩ resistors.
- R5-R6: 100Ω resistors.
- Q1: AO3400A N-MOSFET.
Output Distribution
- F2-F7: TI TPS259520DSGR listed, but Flux library search found TPS259521/TPS259530/TPS259570 variants more directly than exact TPS259520. Verify exact JLC orderable MPN and Flux footprint before use.
- Current-sense resistor: UNI-ROYAL MS122WF100MT4E, C68609, quantity 8.
- Enable buffer: Nexperia 74LVC1G126GW, C55052, quantity 8.
- Edge connector: WingTAT ED32BGFBK, C5173300, quantity 8.
Deferred Rev B
- LM74610QDGKRQ1 ideal diode / OR controller: not JLC-listed in supplied BoM.
- BSC009NE2LS5 MOSFET, C534276.
Deferred Rev C
- W5500 Ethernet controller and RJMG1S8008101BR MagJack are supplied via Digi-Key, not JLCPCB in this list.
- Extra 74LVC1G126 buffer.
Engineering Review
1. Bellwether 70012-1111 Connector
Flux library search did not find Bellwether 70012-1111. This will likely need a custom/imported part and footprint unless a compatible library part or vendor CAD model is located. A missing-part request was submitted internally.
2. Input eFuse / Hot-Swap Rating
TPS259827ONRGET appears available in Flux/JLCPCB and is a reasonable candidate class for high-current input protection, but it must be checked against the full Dell D750E-S1 input current. A single 15A-class integrated eFuse is not sufficient for a 65A main input path unless the architecture uses multiple parallel/load-segmented paths or the device is only protecting a lower-current branch.
3. Per-Slot eFuse Selection
TPS25952x-class devices are more appropriate for modest per-slot rails than for a 16–20A slot unless paralleling or external FET/hot-swap approaches are used. If each boost daughterboard can draw ~16.7A at full load from 12V, the per-slot protection part must be sized for that current with thermal margin.
4. INA3221 Channel Count
INA3221 has three current/voltage monitor channels. One device is not enough for 8 slots unless only aggregate rails are monitored. For 8 slots, expect at least three INA3221 devices for per-slot current only, plus additional channels for total input or auxiliary rails. For 12 slots, expect four INA3221 devices minimum.
5. Raspberry Pi Pico 2
Pico 2 is attractive for prototyping and JLC availability, but it has no native Ethernet. If Ethernet/Prometheus is in Rev A, add W5500 or use an MCU/module with integrated Ethernet support. If Ethernet is Rev C, Pico 2 is acceptable as a control-plane starter.
6. Edge Connector Current Allocation
The proposed 32-pin allocation uses 10 VIN and 10 GND pins. For a ~16.7A slot, that is about 1.67A per VIN pin and 1.67A per GND pin before derating and contact imbalance. This may be acceptable only if the selected connector's per-contact current rating, plating, temperature rise, and parallel-contact rules support it. Use symmetric interleaving of VIN and GND pins to reduce contact heating and loop inductance.
7. AGND Pins
A separate AGND net on a high-current plug-in power module is risky unless the grounding plan is strict. Prefer a single system ground with Kelvin/sense returns for analog measurements. If AGND is retained, connect it to power ground at one defined point on the daughterboard or measurement front-end, not as a floating or competing return path.
8. Telemetry Signals Across Edge Connector
Analog telemetry signals over a high-current edge connector can pick up noise. Prefer local ADC/current monitor on the daughterboard with digital telemetry if the daughterboard becomes complex. If analog telemetry remains, route with adjacent ground pins, RC filtering, defined source impedance, and ADC protection.
9. Control Pins
EN and FAULT/PGOOD are useful and should remain. MODE and SYNC should be optional/populate-if-needed pins unless the selected boost-controller implementation requires them. SYNC should be treated as a noisy/sensitive clock-like signal and should not run next to analog telemetry.
Edge Connector Pinout Recommendation
For a 32-pin connector, keep the high-level allocation but interleave returns more aggressively.
Table
| Category | Pins | Recommendation |
|---|---|---|
| VIN | 10 | Keep, but distribute across connector, not all grouped together. |
| GND / return | 10–12 | Prefer more GND if removing AGND or unused optional signals. Interleave with VIN. |
| AGND | 0–1 | Prefer no separate AGND; use Kelvin sense / local analog reference instead. |
| EN | 1 | Keep. |
| MODE | 1 | Optional; can become address/config strap if not needed. |
| SYNC | 1 | Optional; place away from analog signals and guard with GND if used. |
| FAULT | 1 | Keep. |
| PGOOD | 1 | Keep. |
| I_IN | 1 | Keep only if analog telemetry is retained. |
| I_OUT | 1 | Keep only if daughterboard output sensing is local analog. |
| TEMP_MOS | 1 | Keep or move to digital telemetry. |
| TEMP_IND | 1 | Keep or move to digital telemetry. |
| VOUT_SENSE | 1 | Keep, with filtering/protection. |
| Spare / ID | 1–2 | Strongly recommended for module detect, board ID, or future telemetry bus. |
Connector Candidates Found in Flux
The exact WingTAT ED32BGFBK still needs verification. Additional card-edge options found in Flux/JLCPCB-compatible library search:
Table
| Candidate | Notes |
|---|---|
| LOTES AAA-PCI-047-K01, LCSC C185939 | 54-terminal PCIe-style card edge connector; verify current/contact rating. |
| XUNPU PCIE-52P80H, LCSC C2982553 | 54-terminal card-edge option; verify datasheet and current rating. |
| LOTES APCI0146-P001A, LCSC C841645 | 69-terminal higher-pin-count card-edge option; may give more power/ground contacts. |
Recommended Changes Before Schematic Capture
- Decide whether Rev A includes Ethernet. If yes, add W5500/MagJack or choose a different MCU architecture now.
- Replace or supplement a single INA3221 with enough monitor channels for the actual slot count.
- Recheck TPS259827/TPS25952x current and thermal limits; avoid using 15A/4A eFuses where 65A/16.7A paths are required.
- Locate/import Bellwether 70012-1111 mechanical footprint before committing board outline and PSU input layout.
- Verify ED32BGFBK per-contact current rating; if marginal, move to 52+ or 69-pin connector or split power across additional contacts.
- Rework AGND strategy into single-ground plus Kelvin sensing unless there is a clear isolation reason.
- Add module-present / ID pins to the edge connector allocation.
Status
Supplied Distribution Board BoM
Power Input & Protection
PSU Control & Sensing
Output Distribution
Deferred Rev B
Deferred Rev C
Engineering Review
1. Bellwether 70012-1111 Connector
2. Input eFuse / Hot-Swap Rating
3. Per-Slot eFuse Selection
4. INA3221 Channel Count
5. Raspberry Pi Pico 2
6. Edge Connector Current Allocation
7. AGND Pins
8. Telemetry Signals Across Edge Connector
9. Control Pins
Edge Connector Pinout Recommendation
Connector Candidates Found in Flux
Recommended Changes Before Schematic Capture
