The KSZ8091 is a single-supply 10Base-T/100Base-TX Ethernet physical-layer transceiver for transmission and reception of data over standard CAT-5 unshielded twisted pair (UTP) cable. The KSZ8091 is a highly-integrated PHY solution. It reduces board cost and simplifies board layout by using on-chip termination resistors for the differential pairs, integrating a low-noise regulator to supply the 1.2V core and by offering a flexible 1.8/2.5/3.3V digital I/O interface.

The KSZ8091MNX and KSZ8091MLX offer the Media Independent Interface (MII), while the the KSZ8091RNx offer the Reduced Media Independent Interface (RMII) for direct connection with MII/RMII-compliant Ethernet MAC processors and switches.

Wake-on-LAN (WOL) provides a mechanism for the KSZ8091 to wake up a system that is in standby power mode. The KSZ8091 provides diagnostic features to facilitate system bring-up and debugging in production testing and in product deployment. Parametric NAND tree support enables fault detection between KSZ8091 I/Os and the board. Microchip's LinkMD® TDR-based cable diagnostics identify faulty copper cabling. 

The KSZ8091RNA and KSZ8091RND are available in a 24-pin (4mm x 4mm) QFN package. The KSZ8091MNX and KSZ8091RNB are available in a 32-pin, lead-free QFN packages.  The KSZ8091MLX is available in a 48-pin (7mm x 7mm) LQFP package.

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• Single-chip 10Base-T/100Base-TX IEEE 802.3 compliant Ethernet transceiver
• Wake-on-LAN (WOL) support with either magic packet, link status change, or robust custom-packet detection
• Power-down and power-saving modes
• MII interface support (KSZ8091MNX, KSZ8091MLX)
• RMII v1.2 interface support with a 50MHz reference clock output to MAC and an option to input a 50MHz reference clock (KSZ8091RNB)
• Back-to-back mode support for a 100Mbps copper repeater
• MDC/MDIO management interface for PHY register configuration
• Programmable interrupt output
• LED outputs for link and activity status indication, plus speed indication for KSZ8091RNB
• On-chip termination resistors for the differential pairs
• Baseline wander correction
• HP Auto MDI/MDI-X to reliably detect and correct straight-through and crossover cable connections with disable and enable option
• Auto-negotiation to automatically select the highest link-up speed (10/100Mbps) and duplex (half/full)
• LinkMD® TDR-based cable diagnostics to identify faulty copper cabling
• Parametric NAND Tree support for fault detection between chip I/Os and the board
• Loopback modes for diagnostics
• Single 3.3V power supply with VDD I/O options for 1.8V, 2.5V, or 3.3V
• Built-in 1.2V regulator for core
• Available in 24-pin (4mm x 4mm) QFN, 32-pin (5mm x 5mm) QFN and 48-pin (7mm x 7mm) LQFP packages