KSZ8721CL - 10/100 Ethernet PHY, MII, 48-LQFP | Microchip
MPN: KSZ8721CL ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.2967 | $7.30 |
| 10 | $7.2967 | $72.97 |
| 100 | $7.2967 | $729.67 |
| 500 | $7.2967 | $3,648.35 |
| 1,000 | $7.2967 | $7,296.70 |
KSZ8721CL Overview
An Ethernet PHY is the physical-layer interface between a network MAC and copper or fiber cabling. It converts digital MAC data into electrical signaling for 10/100 Ethernet networks and receives incoming signals for recovery by the MAC. The KSZ8721 family therefore belongs to the Ethernet interface IC and physical-layer transceiver hierarchy, supporting 10BASE-T copper, 100BASE-TX copper, and 100BASE-FX optical-fiber links.
The KSZ8721 supports 3.3 V single-supply operation and is described by Microchip as operating from 2.5 V to meet low-voltage and low-power requirements. Its mixed-signal design is intended to extend signaling distance while reducing power consumption. The available data confirms MII and RMII host-interface options, but individual MII clock rates, RMII timing limits, transceiver insertion loss, crossover support, and link-distance limits are not supplied here and require manufacturer-datasheet confirmation.
Typical implementation roles include industrial Ethernet controllers, embedded network equipment, single-port Ethernet switches, print servers, and communication equipment. In an MII design, the PHY interfaces through parallel digital signals to a MAC or switch engine; in an RMII design, it uses the reduced pin-count interface specified by the host controller. The 48-LQFP package provides 48 external connections but requires careful high-speed signal layout.
A key design consideration is that Ethernet PHY performance depends as much as the IC on magnetic-interface components, crystal timing, controlled-impedance PCB routing, supply bypassing, and isolation from noisy switching circuitry. Verify the exact transceiver mode, pin names, recommended magnetics, termination, and reference schematic against the current Microchip datasheet before layout release.
This product data consolidates verified distributor availability, package information, interface capabilities, and technical-source links with application guidance and transparent data-gap markers. It is intended to accelerate sourcing and initial engineering review without replacing the manufacturer datasheet or schematic-level validation.
Drop-in alternatives for KSZ8721CL — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with KSZ8721CL (same form factor and footprint) — differing in Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
KSZ8721BLI
✅ Drop-In📋 Reference alternative (not in catalog)
KS8721BL
✅ Drop-In📋 Reference alternative (not in catalog)
KSZ8721CL Specifications
| Product Type | 10/100BASE-TX/FX Ethernet physical-layer transceiver |
| Number of Drivers | 1 driver |
| Number of Receivers | 1 receiver |
| Ethernet Modes | 10BASE-T, 100BASE-TX, and 100BASE-FX |
| Host Interface | MII and RMII |
| Distributor Interface Designation | Full MII |
| Supply Voltage | 3 V to 3.6 V |
| Single-Supply Description | 3.3 V single power supply |
| Manufacturer Low-Voltage Operation Statement | 2.5 V operation |
| Package | 48-LQFP, 7 x 7 mm |
| Mounting Type | Surface mount |
| Packaging | Tray |
| Lead-Free Status | Lead free |
| Ethernet Standard | IEEE 802.3u |
| Data Rate Support | 10 Mbps and 100 Mbps |
KSZ8721CL 48-lqfp, 7 x 7 mm Pin Configuration Guide
Pin configuration for KSZ8721CL (48-lqfp, 7 x 7 mm package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for KSZ8721CL.
Refer to the datasheet for full pin configuration.
Typical Applications
KSZ8721CL is suitable for 6 applications: Industrial Embedded Ethernet Controller, Single-Port Ethernet Switch, Print Server and Network Appliance, Fiber-Optic Network Endpoint, Communication Equipment, Low-Power Embedded Network Control.
Industrial Embedded Ethernet Controller
The KSZ8721CL fits an embedded controller that needs 10 Mb/s and 100 Mb/s Ethernet connectivity over copper and optional fiber. Its verified MII interface supports a conventional parallel MAC connection, while RMII provides an alternative for host-controller architectures. Place the PHY beside the MAC or Ethernet controller, use a referenced crystal or clock implementation, and apply the manufacturer bypass network. Compared with a discrete magnetics and transceiver solution, the integrated PHY can reduce design effort, but final qualification still requires confirmation of temperature rating, EMC performance, and lifecycle availability.
Recommended
Single-Port Ethernet Switch
KSZ8721CL can serve one 10/100 Ethernet port in a managed or unmanaged switch design where a switch engine or processor requires a physical-layer device. Its 48-LQFP package exposes Full MII capabilities, and the verified PHY supports both copper and fiber modes. Use controlled-impedance traces for the parallel host interface and follow the specified magnetic or optical component network for the selected medium. The key design trade-off is that the 48-LQFP footprint requires careful high-density assembly and exposes more host-interface routing than an RMII-only implementation.
Recommended
Print Server and Network Appliance
The KSZ8721CL is suitable for print servers, copier interfaces, and compact network appliances that need deterministic 10BASE-T or 100BASE-TX attachment to an embedded processor. The verified Full MII designation is useful when the host processor already supports parallel Ethernet timing. Its low-power design objective helps systems with constrained thermal budgets, although actual current and dissipation values are not present in the supplied data. Validate standby behavior, startup sequencing, link-flossup handling, and transformer selection against the current manufacturer documentation.
Recommended
Fiber-Optic Network Endpoint
Use the KSZ8721CL's verified 100BASE-FX capability when an endpoint needs a Fast Ethernet fiber link rather than only copper connectivity. The PHY interfaces to a MAC through MII or RMII, while the external optical hardware must complete the physical medium path. Pin-compatible replacement decisions must preserve 100BASE-FX support, not merely Ethernet speed and package count. Before layout, confirm the required optical signal interface, termination, isolation, and reference magnetics because those details are absent from the supplied search evidence.
Recommended
Communication Equipment
KSZ8721CL can provide the Fast Ethernet physical layer in embedded communication equipment that links a processor or protocol engine to a 10/100 network. Both MII and RMII are identified in the verified sources, allowing the designer to match the host controller's preferred signaling style and board-space budget. The PHY should be connected according to the official reference layout with short clock routes, continuous supply return paths, and approved network components. Long lifecycle guarantees, temperature limits, and detailed EMC margins were not supplied, so they require separate manufacturer confirmation.
Recommended
Low-Power Embedded Network Control
The KSZ8721CL targets low-voltage, low-power operation while supporting 10 Mb/s and 100 Mb/s Ethernet, making it relevant to compact embedded controllers with constrained power budgets. The listed package is a 48-LQFP in tray packaging, which can simplify prototype and low-to-moderate-volume assembly planning. Designers should evaluate link-state power, regulator efficiency, magnetics loss, thermal rise, and standby requirements together because the supplied sources do not provide numeric current or thermal specifications. A comparison of measured board-level consumption is preferable to estimating from the low-power description alone.
Recommended
Recommended Products Summary
Engineering reference data for KSZ8721CL — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | KSZ8721BLI | KS8721BL |
|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 48-LQFP (7 x 7 mm) | 48-LQFP | 48-LQFP |
| Supply Voltage | 3 V to 3.6 V; 3.3 V single-supply description | 2.5 V and 3.3 V shown in comparison context | 2.5 V and 3.3 V |
| Verified Pin Compatibility | Target device | Not independently established; circuit structure and parameters reported as inconsistent | Not established; comparison warns of parameter and circuit differences |
Key Differentiators
- Verified multi-medium Ethernet support (vs KSZ8721BLI)
- Host-interface flexibility (vs KS8721BL)
- Distributor-identified Full-MII configuration (vs KS8721BL)
Design Notes
Route MII, RMII, and clock signals on controlled-impedance PCB layers using the manufacturer's reference stack-up and trace rules. Keep the PHY and its decoupling close to the associated MAC or switch engine, provide a continuous return plane beneath high-speed routes, and avoid test pads or long stubs where they interrupt timing-sensitive signals. The supplied sources do not provide trace-length tolerances, so numerical layout constraints must be taken from the current datasheet and reference design.
Separate Ethernet PHY clock and signal routing from noisy switching nodes, inductors, and high-current return paths. Preserve the component placement and ground topology shown by Microchip when selecting crystal circuitry, magnetic-interface parts, or termination networks. Because 100BASE-FX and copper ports require different external networks, do not substitute media components based solely on package or speed; verify every network component against the supported operating mode.
Do not treat a related Microchip PHY as a drop-in substitute merely because it has a 48-LQFP package. KSZ8721CL is verified for 10BASE-T, 100BASE-TX, 100BASE-FX, MII, and RMII, while supplied comparison data warns that KSZ8721BLI and KS8721BL differ in parameters or circuit structure. Confirm pin names, strap options, register behavior, clocking, supply sequencing, magnetic components, and firmware support before approving a replacement.
Compliance Information
The supplied distributor snippet identifies KSZ8721CL as lead free. No conclusive RoHS, REACH, halogen-free, conflict-minerals, or automotive-qualification statement was provided.
