General Description
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, by 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 offers the Media Independent Interface (MII) and the KSZ8091RNB offers the Reduced Media Independent Interface (RMII) for direct connection with MII/RMII-compliant Ethernet MAC processors and switches.
Energy Efficient Ethernet (EEE) provides further power saving during idle traffic periods and 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. Micrel LinkMD® TDR-based cable diagnostics identify faulty copper cabling.
The KSZ8091MNX and KSZ8091RNB are available in 32-pin, lead-free QFN packages (see “Ordering Information”).
Datasheets and support documentation are available on Micrel’s web site at: www.micrel.com.

Features
• Single-chip 10Base-T/100Base-TX IEEE 802.3 compliant Ethernet transceiver
• MII interface support (KSZ8091MNX)
• 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)
• Energy Efficient Ethernet (EEE) support with low-power idle (LPI) mode and clock stoppage (MII version only) for 100Base-TX and transmit amplitude reduction with 10Base-Te option
• Wake-on-LAN (WOL) support with either magic packet, link status change, or robust custom-packet detection