Compact PLC CPU Module Reference Design
An illustrative compact PLC CPU module design for production-line equipment, packaging machinery, water treatment and building automation: DC 24V input, dual-port Ethernet (built-in 10/100 switch IC, daisy-chain capable, for programming, Modbus TCP and other industrial Ethernet communication), isolated RS-485 port on DB9 (Modbus RTU / free port), backplane expansion bus to I/O expansion modules, USB Type-C programming port, microSD program card and FRAM retentive memory. This page lists the function, selection notes and VOOHU part numbers for 28 component positions.
Illustrative PCB ⇄ Schematic
Use the board view to see layout and component positions; click any position for selection notes, recommended part numbers and package. The board is a schematic layout arranged by functional zone (not the actual layout); Ethernet ports, RS-485 port, backplane expansion connector, programming port, program card and power terminal all sit on the bottom edge, and I/O expansion modules are external nodes.
Ports P1 / P2 are identical; only 1 port and 1 differential pair are drawn (the other 10/100 pair is the same). RJ45 J1 is a 1 × 2 plain jack without magnetics; each port goes through a VOOHU discrete 10/100 LAN transformer (T1 / T2, WHS16037TG, 1500 Vrms isolation), is clamped on the chip side by ESD arrays D1 / D2, and connects to a copper port of the 10/100 switch IC JL5104C-NI with integrated PHYs; the switch RMII port connects to the MPU MAC, and crystal Y1 provides the reference clock. Center-tap connection, termination and crystal load capacitor values per the switch IC datasheet.
Board bill of materials
Click any row to jump to that position and view its selection notes
| No. | Zone | Position | Ref. | VOOHU category | Recommended part | Availability |
|---|---|---|---|---|---|---|
| 01 | A Dual-port Ethernet | RJ45 dual port (1 × 2, with LEDs) | J1 | RJ45 Connectors | SYT561288AB2A3DY1027 | VOOHU |
| 02 | A Dual-port Ethernet | 10/100 LAN transformer ×2 | T1 T2 | 10/100 LAN Transformers | WHS16037TG | VOOHU |
| 03 | A Dual-port Ethernet | Ethernet ESD array ×2 | D1 D2 | TVS / ESD | WHALD03G4U | VOOHU |
| 04 | A Dual-port Ethernet | 10/100 switch IC (integrated PHYs) | U1 | Ethernet Switch ICs | JL5104C-NI | VOOHU |
| 05 | A Dual-port Ethernet | Switch IC crystal | Y1 | — | — | Non-VOOHU |
| 06 | B RS-485 | DB9 female (RS-485 port) | J2 | D-SUB Connectors | WHB050XX6X1ADB2 | VOOHU |
| 07 | B RS-485 | Gas discharge tube (stage 1) | G1 | GDT | WHGD200V1P0B | VOOHU |
| 08 | B RS-485 | Bus TVS (stage-2 clamp) | D3 | TVS / ESD | WHALD30E2B | VOOHU |
| 09 | B RS-485 | Bus differential-line common-mode choke | L1 | Signal Line CMC | WHAC-4532A-601T0 | VOOHU |
| 10 | B RS-485 | Isolated RS-485 transceiver | U2 | — | — | Non-VOOHU |
| 11 | C Expansion · Programming | Backplane expansion bus connector | J3 | — | — | Non-VOOHU |
| 12 | C Expansion · Programming | Backplane bus transceiver | U3 | — | — | Non-VOOHU |
| 13 | C Expansion · Programming | USB Type-C programming port (USB 2.0 only) | J4 | USB / Type-C | WHTCAX01167303 | VOOHU |
| 14 | C Expansion · Programming | USB ESD array | D4 | TVS / ESD | WHTA5V01P2C | VOOHU |
| 15 | C Expansion · Programming | microSD card socket | J5 | SD Card Sockets | WHTF190T123101W | VOOHU |
| 16 | D Core | Main processor (MPU) | U4 | — | — | Non-VOOHU |
| 17 | D Core | DDR3L memory | U5 | — | — | Non-VOOHU |
| 18 | D Core | eMMC program storage | U6 | — | — | Non-VOOHU |
| 19 | D Core | Retentive memory (FRAM) | U7 | — | — | Non-VOOHU |
| 20 | D Core | Main crystal + RTC crystal | Y2 Y3 | — | — | Non-VOOHU |
| 21 | D Core | Core supply filter molded inductor ×2 | L2 L3 | Molded Inductors | WHYTA0420 Series | VOOHU |
| 22 | E Power | DC 24V input terminal | J6 | — | — | Non-VOOHU |
| 23 | E Power | Input fuse + TVS | F1 D5 | TVS / ESD | WHTB058VA | VOOHU |
| 24 | E Power | Power line common-mode choke (EMI) | L4 | Power Line CMC | WHAL-7060A-102T0 | VOOHU |
| 25 | E Power | Synchronous buck ×2 (24V→5V→3.3V) | U8 U9 | — | — | Non-VOOHU |
| 26 | E Power | DC-DC molded inductor ×2 | L5 L6 | Molded Inductors | WHYT0630 Series | VOOHU |
| 27 | E Power | Push-pull isolated power transformer | T3 | Push-Pull Transformers | WHST06K14A0 | VOOHU |
| 28 | E Power | Push-pull driver + isolated-side LDO | U10 U11 | — | — | Non-VOOHU |
Resources & downloads
Board bill of materials
Reference designators, zones, VOOHU categories, recommended parts and availability for all 28 positions. Opens directly in Excel.
Datasheet collection
Datasheet PDFs for the VOOHU parts recommended on this board.
Design files & footprint library
Schematic, PCB, and VOOHU part footprints and 3D models.
Coming soonRequest the PLC reference design full package
Includes the BOM, datasheets of the recommended VOOHU parts and per-position selection notes. If you need selection advice for your port count, fieldbus type or expansion scheme, describe it in the requirement field. We reply within 24 hours on working days.
