PRELIMINARY
Publication# 22235 Rev: I Amendment/0
Issue Date: April 2001Refer to AMD’s Website (www.amd.com) for the latest information.

Am79C874
NetPHY™-1LP Low Power 10/100-TX/FX Ethernet Transceiver
DISTINCTIVE CHARACTERISTICS
a73 10/100BASE-TX Ethernet PHY device with
100BASE-FX fiber optic support
a73 Typical power consumption of 0.3 W
a73 Sends/receives data reliably over cable lengths
greater than 130 meters
a73 MII mode supports 100BASE-X and 10BASE-T
a73 7-Wire (General Purpose Serial Interface (GPSI))
mode supports 10BASE-T
a73 Three PowerWise™ management modes (from
300 mW typical)
— Power down: only management responds
Typical power = 3 mW
— Unplugged: no cable, no receive clock
Typical power = 100 mW
— Idle wire: no wire signal, no receiver power
Typical power = 285 mW; MAC saves over
100 mW
a73 Supports 1:1 or 1.25:1 transmit transformer
— Using a 1.25:1 ratio saves 20% transmit
power consumption
— No external filters or chokes required
a73 Waveshaping – no external filter required
a73 Full and half-duplex operation with full-featured
Auto-Negotiation function
a73 LED indicators: Link, TX activity, RX activity,
Collision, 10 Mbps, 100 Mbps, Full or Half
Duplex
a73 MDIO/MDC operates up to 25 MHz
a73 Automatic Polarity Detection
a73 Built-in loopback and test modes
a73 Single 3.3-V power supply with 5-V I/O tolerance
a73 12 mm x 12 mm 80-pin TQFP package
a73 Support for industrial temperature
(-40°C to +85°C)
GENERAL DESCRIPTION
The Am79C874 NetPHY-1LP device provides the phys-
ical (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 Ether-
net 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 fil-
tering 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 Inter-
face (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 po-
larity 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 25-
MHz 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) tempera-
ture ranges. The industrial temperature range is well
suited to environments, such as enclosures with re-
stricted air flow or outdoor equipment.