The Am79C875 NetPHY-4LP device integrates four physical layer 10/100 Ethernet transceivers into a 100-pin PQFP package, and delivers industry standard functionality in the smallest package with extremely low power. The 14x20mm package conserves valuable board space in high-port count switches and other network applications. The NetPHY-4LP device operates at 3.3V and is optimized for low power operation. With power consumption of only 1.3W, customers can realize immediate cost benefits by reducing the size of power supplies and the need for system fans, optimizing system cost per port. An option for further power reduction to 1.2W or 0.28W per port is also available. Furthermore, PowerWise™ power management modes provide options for even lower power consumption levels. Power Down is available on a per port basis.

Reduced MII™ (RMII) is provided for switch and RMII repeater applications, where the pin count reduction is a key benefit to switch controller ASICs and system cost savings. RMII saves 9 pins per port when compared with the traditional MII interface. The NetPHY-4LP device provides the physical (PHY) layer transceiver functions for four 10/100 Mbps Ethernet ports and is fully IEEE 802.3u and Auto-Negotiation compliant. Auto-Negotiation determines the network speed and full or half-duplex operation. Automatic polarity correction is performed during Auto-Negotiation and during 10BASE-T signal reception. Multiple LED pins are provided for front panel status feedback. Individual LEDs can indicate link detection, speed, and data being transmitted/received.

The NetPHY-4LP device can receive and transmit data reliably at over 125 meters on each port. On-chip input filtering and output waveshaping for unshielded twisted pair operation over Category 5 cables is included. No external filters or chokes are required. The NetPHY-4LP can use either 1:1 isolation transformers or 1.25:1 isolation transformers. 1.25:1 isolation transformers provide 20% lower transmit power consumption, reducing power consumption to 1.2W. A PECL interface is available for 100BASE-FX applications.

The NetPHY-4LP device can function across the Industrial Temperature range of -40°C to +85°C. This is the lowest power multi-port PHY available for Embedded, Telecom and Industrial Control applications and for designs used in outdoor environments or with little airflow.

NetPHY-4LP Product Features

• Four 10/100BASE-TX Ethernet PHY transceivers
• Small, space-saving 100-pin PQFP package
• Single 3.3 volt power supply with 5-V I/O tolerances
• Typical power consumption of 1.2-1.3 Watts
• Four RMII ports for interface to switch and RMII repeater applications
• 125 meter MLT-3 and Baseline Wander operation
• Waveshaping and on-chip filtering for 10BASE-T
• PowerWise™; power management modes (from 300mW, typical per port)
  -- Power Down per port: only management responds, 3mW typical power per port
  -- Unplugged: no cable, no receiver power, 100mW typical power per port (default)
  　
• Selectable 1:1 or 1.25:1 transmit transformer
  -- Using a 1.25:1 ratio saves 20% power consumption (1.2W per device)
  　
• No external filters or chokes required
• Supports full Auto-Negotiation operation with duplex and speed selection per port
• LED indicators: LINK, TX activity, RX activity, Speed: 100 or 10, Duplex: full or half, Collision
• Automatic Polarity Detection
• 100BASE-FX fiber optic support on one port (port 3)
• Compliant with IEEE 802.3 standards for 100BASE-TX, -FX and 10BASE-T
• Built-in loopback and test modes
• Industrial Temperature (-40°C to +85°C) option

• Enables "step-and-repeat" design in multiples of four ports
  -- fits neatly behind magnetics and dual stacked RJ-45 connectors
• Saves PCB real estate when compared to 208-pin packages (see diagram below)