D A T A
S H E E T
Am79C874
NetPHY™-1LP Low Power 10/100-TX/FX Ethernet Transceiver
DISTINCTIVE CHARACTERISTICS
■ Supports 1:1 or 1.25:1 transmit transformer
■ 10/100BASE-TX Ethernet PHY device with
100BASE-FX fiber optic support
— Using a 1.25:1 ratio saves 20% transmit
power consumption
■ Typical power consumption of 0.3 W
— No external filters or chokes required
■ Sends/receives data reliably over cable lengths
greater than 130 meters
■ MII mode supports 100BASE-X and 10BASE-T
■ 7-Wire (General Purpose Serial Interface (GPSI))
mode supports 10BASE-T
■ Three PowerWise™ management modes (from
300 mW typical)
■ Waveshaping – no external filter required
■ Full and half-duplex operation with full-featured
Auto-Negotiation function
■ LED indicators: Link, TX activity, RX activity,
Collision, 10 Mbps, 100 Mbps, Full or Half
Duplex
■ MDIO/MDC operates up to 25 MHz
— Power down: only management responds
Typical power = 3 mW
■ Automatic Polarity Detection
— Unplugged: no cable, no receive clock
Typical power = 100 mW
■ Single 3.3-V power supply with 5-V I/O tolerance
— Idle wire: no wire signal, no receiver power
Typical power = 285 mW; MAC saves over
100 mW
■ Support for industrial temperature
(-40°C to +85°C)
■ Built-in loopback and test modes
■ 12 mm x 12 mm 80-pin TQFP package
GENERAL DESCRIPTION
The Am79C874 NetPHY-1LP device provides the
physical (PHY) layer and transceiver functions for one
10/100 Mbps Ethernet port. It delivers the dual benefits
of CMOS low power consumption and small package
size. Operating at 3.3 V, it consumes only 0.3 W. Three
power management modes provide options for even
lower power consumption levels. The small 12x12 mm
80-pin PQL package conserves valuable board space
on adapter cards, switch uplinks, and embedded Ethernet applications.
The NetPHY-1LP 10/100 Mbps Ethernet PHY device is
IEEE 802.3 compliant. It can receive and transmit data
reliably at over 130 meters. It includes on-chip input filtering and output waveshaping for unshielded twisted
pair operation without requiring external filters or
chokes. The NetPHY-1LP device can use 1:1 isolation
transformers or 1.25:1 isolation transformers. 1.25:1
isolation transformers provide 20% lower transmit
power consumption. A PECL interface is available for
100BASE-FX applications.
Interface to the Media Access Controller (MAC) layer is
established via the standard Media Independent Interface (MII), a 5-bit symbol interface, or a 7-wire (GPSI)
interface. 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. One option is to use two bi-color LEDs to
show when the device is in 100BASE-TX or 10BASE-T
mode (by illuminating), Half or Full Duplex (by the
color), and when data is being received (by blinking).
Individual LEDs can indicate link detection, collision
detection, and data being transmitted.
The NetPHY-1LP device needs only one external 25MHz oscillator or crystal because it uses a dual-speed
clock synthesizer to generate all other required clock
domains. The receiver has an adaptive equalizer/DC
restoration circuit for accurate clock/data recovery from
the 100BASE-TX signal.
The NetPHY-1LP device is available in the commercial
(0°C to +70°C) or industrial (-40°C to +85°C) temperature ranges. The industrial temperature range is well
suited to environments, such as enclosures with restricted air flow or outdoor equipment.
Always check www.amd.com for the latest information.
Publication# 22235 Rev: K
Issue Date: May 2005
