KSZ8721BL - 100Mbps Ethernet PHY | Microchip | LQFP-48
MPN: KSZ8721BL ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
KSZ8721BL Overview
An Ethernet physical-layer transceiver, or Ethernet PHY, converts digital MAC data into electrical or optical signaling suitable for a network medium and converts received signals back into digital data. The PHY sits between a host controller and the physical network medium, commonly using an MII or RMII interface. The KSZ8721BL therefore belongs to the Ethernet interface hierarchy: transceiver, network interface controller companion, interface IC, and semiconductor.
Key verified features include 100 Mbps operation, MII and RMII host-interface support, 10/100BASE-TX and 100BASE-FX capability, automatic MDI/MDI-X crossover, 3.3 V single-supply operation, and a 2.5 V core. The commercial temperature range is 0°C to +70°C. The reported supply current is 151 mA, while the exact pin mapping, package dimensions, transceiver electrical limits, and full timing values are not all available in the supplied excerpts.
The device is suitable when an embedded processor, microcontroller, FPGA, or Ethernet controller needs an Ethernet media-access solution without implementing analog PHY circuitry on the PCB. Its RMII interface can reduce host-side wiring compared with MII, while MII support provides compatibility with systems designed around parallel Ethernet control signals. The integrated 2.5 V core is relevant to low-voltage processor ecosystems and power-conscious embedded equipment.
Typical applications include industrial Ethernet equipment, embedded gateways, set-top boxes, printers, game or media systems, network adapters, and control systems with 10/100BASE-T connectivity. Fiber-capable 100BASE-FX support can also suit equipment intended for longer-distance point-to-point links when the required optical partner and external implementation are present.
When designing around KSZ8721BL, confirm the exact package variant and pinout against the manufacturer datasheet, preserve the required decoupling and media-interface layout, and verify the external magnetics or fiber components required by the selected network medium. The supplied data confirms the commercial temperature grade and 48-pin LQFP option, but does not establish RoHS, REACH, AEC-Q100, or halogen-free status.
This product page consolidates the verified manufacturer description, technical identifiers, source links, and application guidance into an engineering-oriented reference for the KSZ8721BL Ethernet PHY.
Drop-in alternatives for KSZ8721BL — 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 KSZ8721BL (same form factor and footprint) — differing in Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
KSZ8721BT
✅ Drop-In✓ In Stock
$4.3191 / Unit
View Datasheet →KSZ8721B
✅ Drop-In✓ In Stock
$5.4078 / Unit
View Datasheet →KSZ8721SL
✅ Drop-In📋 Reference alternative (not in catalog)
KSZ8721BL Specifications
| Product Type | 10/100BASE-TX/FX MII physical-layer transceiver |
| Data Rate | 100 Mbps |
| Supply Voltage | 3.3 V |
| Core Voltage | 2.5 V |
| Host Interface | MII and RMII |
| Ethernet Type | 10/100BASE-TX/FX |
| Operating Temperature Range | 0°C to +70°C |
| Supply Current | 151 mA |
| Number of Pins | 48 |
| Package | 48-pin LQFP |
| MDI/MDI-X | Automatic crossover supported |
| Power-Supply Architecture | 3.3 V single power supply with 2.5 V core |
| Media Support | 10BASE-T/100BASE-TX/100BASE-FX |
| Temperature Grade | Commercial |
| Mounting Type | Surface mount |
| Interface Type | MII/RMII Ethernet interface |
KSZ8721BL 48-pin lqfp Pin Configuration Guide
Pin configuration for KSZ8721BL (48-pin lqfp 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 KSZ8721BL.
Refer to the datasheet for full pin configuration.
Typical Applications
KSZ8721BL is suitable for 8 applications: Embedded Ethernet Gateway, Industrial Control Terminal, Network Adapter, Printer and Peripheral Connectivity, FPGA-Based Communication Card, 100BASE-FX Point-to-Point Link, Set-Top Media Device, Low-Voltage Embedded Platform.
Embedded Ethernet Gateway
The KSZ8721BL fits an embedded Ethernet gateway that needs a dedicated 10/100 Ethernet media interface beside a microcontroller or application processor. Its 100 Mbps capability matches Fast Ethernet designs, while MII and RMII allow the host architecture to choose parallel signaling appropriate to board space and processor resources. The 3.3 V supply and 2.5 V core are useful when the surrounding digital system operates at low voltage, although the host must still meet the device’s exact rail and timing requirements. Automatic MDI/MDI-X crossover simplifies cable installation.
Recommended
Industrial Control Terminal
KSZ8721BL can support a commercial-temperature Ethernet port in an industrial control terminal, provided the enclosure temperature remains within the verified 0°C to +70°C range. The 10/100BASE-TX capability provides a practical link to supervisory networks, while MII/RMII connects to a controller without requiring a host to implement the PHY analog front end. The automatic crossover feature reduces installation friction. For wider industrial environments, verify whether the selected system variant and sourcing conditions meet the required temperature and reliability specifications.
Recommended
Network Adapter
The KSZ8721BL is suited to a 10/100 network adapter where an existing controller needs copper Ethernet connectivity. Placing the PHY behind the host’s MII or RMII interface keeps the physical medium implementation separate from the controller logic, while the 100 Mbps rating aligns with Fast Ethernet equipment. The 48-pin LQFP option is important for designers who are maintaining a leaded surface-mount footprint. MDI/MDI-X auto-crossover allows the adapter to support more common straight-through cable arrangements without adding a manual crossover switch.
Recommended
Printer and Peripheral Connectivity
A printer, scanner, or other networked peripheral can use the KSZ8721BL for a 10/100BASE-T connection when the host controller supports MII or RMII. The transceiver’s 100 Mbps rate is appropriate for legacy and cost-sensitive Fast Ethernet networks, and the 3.3 V single-supply description simplifies power planning compared with older multi-rail PHY designs. The 2.5 V core may align with contemporary embedded processors, but the complete datasheet must be checked for I/O levels, timing, reset, clock, and exposed thermal or power requirements before layout release.
Recommended
FPGA-Based Communication Card
The KSZ8721BL can provide the Ethernet physical layer for an FPGA-based communication card when the FPGA logic implements or connects to an appropriate MAC and supports MII or RMII timing. Using RMII can reduce host-side pin count compared with a full MII implementation, which is useful when the FPGA package and board routing are constrained. The device’s 100 Mbps capability matches many FPGA control, monitoring, and data-acquisition systems. The design must account for clock tolerance, RMII/MII mode configuration, MDIO management, reset sequencing, and the required Ethernet medium components.
Recommended
100BASE-FX Point-to-Point Link
The KSZ8721BL’s stated 100BASE-FX capability makes it relevant to equipment that needs an optical point-to-point option alongside copper Ethernet. In such a design, the PHY is paired with the required optical transceiver or media-conversion circuitry, while MII or RMII connects it to the system controller. The copper and fiber feature set can simplify product variants, but optical implementation details such as link budget, wavelength, connector, and isolation are not provided in the verified excerpts. Those parameters must be established from the full manufacturer documentation and the selected optical components.
Recommended
Set-Top Media Device
The KSZ8721BL can serve a set-top or media device that needs a low-cost Fast Ethernet management and control link. The 100 Mbps rate is more than sufficient for many control-plane, firmware-update, and telemetry functions, while MII or RMII allows interface selection according to the host processor. The commercial temperature rating is appropriate only where the enclosure remains within 0°C to +70°C. Design engineers should validate boot ordering, clock sources, MDIO firmware, magnetics selection, and connector isolation because those details are not present in the supplied verified excerpts.
Recommended
Low-Voltage Embedded Platform
KSZ8721BL is a candidate for low-voltage embedded platforms because its verified description combines a 3.3 V single supply with a 2.5 V core. This can help systems built around processors with 2.5 V I/O or internal rails avoid an older, higher-voltage PHY architecture, subject to exact interface-level compatibility. The MII/RMII choice permits adaptation to the processor’s available pins, and 100 Mbps is adequate for control, logging, and management traffic. Before committing, verify the host voltage levels, timing, power sequencing, and PHY configuration registers in the complete datasheet.
Recommended
Recommended Products Summary
Engineering reference data for KSZ8721BL — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | KSZ8721BT | KSZ8721B | KSZ8721SL |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 48-pin LQFP | 48-pin LQFP footprint; verify exact suffix package | 48-pin LQFP footprint; verify exact suffix package | 48-pin LQFP footprint; verify exact suffix package |
Key Differentiators
- Supports both MII and RMII host interfaces (vs KSZ8721BT)
- Includes automatic MDI/MDI-X crossover (vs KSZ8721BT)
- Supports 10/100BASE-TX/FX media (vs KSZ8721BT)
- Commercial 0°C to +70°C temperature range (vs KSZ8721BT)
Design Notes
Design the power rails around the verified 3.3 V single supply and 2.5 V core architecture, but do not infer voltage tolerances or sequencing from the overview alone. Place the required bypass capacitors at the device supply pins and keep the high-frequency return path short. Confirm the absolute maximum and operating limits, core-rail decoupling, power-up order, and reset behavior in the manufacturer datasheet before final schematic release.
Use the manufacturer’s recommended Ethernet layout for the MII/RMII host interface and the selected copper or fiber media. Keep the MDI/TX/RX differential pairs appropriately controlled, minimize stubs and unnecessary vias, and provide a continuous return path. The automatic MDI/MDI-X feature does not eliminate the need for correct differential routing, magnetics, or optical-partner implementation.
Do not substitute a related KSZ8721 suffix solely because the devices share the family name or datasheet. Confirm the exact 48-pin LQFP footprint, pin names, MII/RMII configuration, MDIO behavior, temperature grade, and media features against the ordered MPN. The supplied comparison data supports KSZ8721BT as a stated drop-in replacement, but it does not provide complete quantitative data for every alternative.
Account for the host clock and reset requirements of the selected MII or RMII mode. Validate timing against the fastest system clock and ensure the controller, PHY, and magnetics share a compatible ground and reference strategy. For RMII designs, check whether the clock source, PHY mode, and 50 MHz-class interface assumptions match the host platform; the supplied excerpts do not provide those timing values.
Compliance Information
The supplied verified excerpts do not establish RoHS, REACH, lead-free, halogen-free, conflict-mineral, or automotive qualification status. AEC-Q100 is not applicable because the verified operating-temperature description identifies a commercial-grade device, but the compliance conclusion is based only on the supplied data.
