Lan 78Q2123


Gerneral Description

Housed in a 32-lead QFN package, the 78Q2123 MicroPHY is the smallest Fast Ethernet PHY available that provides a full 802.3 Media Independent Interface (MII) to the system Media Access Controller. With HP Auto-MDI/X, the 78Q2123 is ideal for consumer applications.

The MicroPHY includes integrated MII, ENDECs, scrambler/descrambler, dual-speed clock recovery, and full-featured auto-negotiation functions. The transmitter includes an on-chip pulse-shaper and a low-power line driver. The receiver has an adaptive equalizer and a baseline restoration circuit required for accurate clock and data recovery. The transceiver interfaces to Category-5 unshielded twisted pair (Cat-5 UTP) cabling for 100BASE-TX applications, and Category-3 unshielded twisted pair (Cat-3 UTP) for 10BASE-T applications. The MDI is connected to the line media via dual 1:1 isolation transformers. No external filter is required. Interface to the MAC is accomplished through an IEEE-802.3 compliant Media Independent Interface (MII). The 78Q2123 is designed to serve the embedded Ethernet market, tailored specifically to the needs of game consoles, broadband modems, printers, set top boxes and audio/visual equipment. It is designed for low-power consumption and operates from a single 3.3V supply. The 78Q2123 is rated for commercial temperature range. Reference the 78Q2133 for industrial temperature range.


  • 10BASE-T/100BASE-TX IEEE-802.3 compliant TX and RX functions requires only a dual 1:1 isolation transformer interface to the line
  • Integrated MII, 10BASE-T/100BASE-TX ENDEC, 100BASE-TX scrambler/descrambler, and full-featured auto-negotiation function
  • Full/Half duplex operation
  • Automatic MDI/MDI-X cross over correction
  • Register-programmable transmit amplitudes, Interrupt, and LED outputs
  •  Automatic polarity correction during auto-negotiation and 10BASE-T signal reception
  • Power-saving and power-down modes including transmitter disable
  • Small Package: 32-QFN (5×5 mm)
  • Low Power (~290mW)
  • Single 3.3 V +/- 0.3V Supply
  •  78Q2123 rated for 0°C to 70°C operation