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WIZnet’s Ethernet chip design guide is a hardware reference for engineers implementing a WIZnet controller on a PCB. It covers areas such as MDI and MII signals, power, component placement, the Ethernet socket, EMI/compliance and, where applicable, PoE. The essential first step is to select the exact chip, then use that part’s datasheet, errata and reference schematic alongside the guide; circuits and layout choices should not be assumed to apply unchanged across the WIZnet family.
What the WIZnet hardware design guide covers
WIZnet describes its guide as PCB design reference material, not a general networking tutorial. Its subject matter is the circuit and board implementation around the controller: signal connections, power, placement and Ethernet-related board design.
The guide webpage lists W5100, W5300, W5500, W7100A, W7500 and W7500P. The English PDF gives a different chip list—W5100, W5300, W5500, W6300, W7500 and W7500P—and identifies sections on schematic design, PCB design, compliance, EMI and PoE. These lists are not identical, so check the document itself for the part you are designing around. WIZnet Hardware Design Guide · English hardware design guide PDF
WIZnet warns that not following the guide’s instructions may lead to degraded Ethernet performance. That is a manufacturer warning, not a quantified result: the guide materials cited here do not establish a specific performance penalty or a universal set of numerical layout rules.
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Start with the exact controller and its documents
Do not begin by copying a schematic from a different WIZnet chip. Choose the controller first, then consult its official datasheet and errata, locate its matching reference schematic, and use the relevant guide sections to review the design. Datasheet electrical limits and chip-specific documentation—not product-summary figures—should govern the circuit.
- Identify the exact part. Confirm the chip designation and the host interface your system needs.
- Open the current datasheet and errata. Check electrical requirements, package details, protocol behavior and any corrections or limitations for that part.
- Find the matching reference schematic. Use the chip’s own official resources rather than assuming another family member’s circuit is interchangeable.
- Review the board implementation. Work through the guide’s applicable material on MDI/MII, power, component placement, Ethernet socket, compliance and EMI; review PoE material only when it applies to the design.
- Verify clock components against chip-specific guidance. For example, WIZnet’s W5100S document index lists a Crystal Selection Guide v1.0.0, along with Datasheet v1.2.8 and Errata Sheet v1.0.0. W5100S documents
The available guide summaries do not establish numerical impedance targets, decoupling values, crystal tolerances or detailed routing dimensions. Obtain those requirements from the exact chip’s design materials rather than filling in values by analogy.
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- umber of Transceivers: 1 Transceiver Data Rate: 10 Mb/s, 100 Mb/s Interface Type: 8 bit/16 bit, MDI, MDI-X
W5500 vs. W5100S: key design differences
WIZnet’s product overviews distinguish these chips in their host interfaces and internal resources. The figures below are manufacturer-published feature summaries, not substitutes for datasheet electrical limits.
| Design axis | W5500 | W5100S |
|---|---|---|
| Host interface | SPI, up to 80 MHz, per WIZnet’s product overview | SPI up to 70 MHz or parallel system bus, per WIZnet’s product overview |
| Hardware sockets | 8 independent sockets | 4 independent sockets |
| Internal TX/RX memory | 32 KB | 16 KB |
| Ethernet MAC and PHY | Integrated 10/100 MAC and PHY | Integrated 10/100 MAC and PHY |
| Documentation noted by WIZnet | English datasheet v1.1.0 is listed on its product page; reference schematics are in product resources | Document index lists Datasheet v1.2.8, Errata Sheet v1.0.0 and Crystal Selection Guide v1.0.0 |
Sources: W5500 product and documentation page and W5100S product overview.
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Compare the interface and resource budget
The W5500’s listed SPI ceiling is higher, while the W5100S overview also lists a parallel system bus. The W5500 has twice the listed socket count and internal TX/RX memory. Whether those differences matter depends on the host, traffic pattern and application; check the datasheet and reference materials before selecting a part.
Check protocol limitations, not just feature summaries
WIZnet notes that the W5500 does not support IP fragmentation. Product summaries can help narrow candidates, but they do not establish every protocol detail for a design. Verify the exact chip’s datasheet and errata against the network behavior your product requires. W5500 product information · W5100S product information
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Prototype without starting at chip level
If the goal is to add Ethernet to an embedded prototype before designing a controller-level PCB, WIZnet offers official prototyping hardware. A module or evaluation board can reduce the amount of chip-level hardware work in the prototype; it does not remove the need to validate a custom board’s schematic, layout, EMC and qualification.
Quick Recap
- W5500-io: WIZnet describes this compact plug-in module as a way to add Ethernet to embedded systems without complex hardware design. Its product page provides a reference schematic, 3D model and parts list. W5500-io Ethernet module
- W5100S-EVB-Pico2: WIZnet’s documentation links board resources including schematics, board-file references, a 3D file and example firmware. W5100S-EVB-Pico2 resources
Board-review checklist
- Is the design based on the exact controller’s current datasheet, errata and reference schematic?
- Have the applicable MDI/MII, power, placement and Ethernet socket guidance been reviewed?
- Have EMI/compliance considerations—and PoE requirements, if relevant—been addressed for the actual board?
- Have clock components been checked against chip-specific documentation?
- Have host interface, socket and buffer needs, and protocol limitations been checked against the application?
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