78Q8392L

Low Power Ethernet

Coaxial Transceiver

4

PIN DESCRIPTION

NAME

TYPE

DESCRIPTION

CD+*/CD-

O

Collision Output. Balanced differential line driver outputs from the collision detect

circuitry. The 10 MHz signal from the internal oscillator is transferred to these outputs

in the event of collision, excessive transmission (jabber), or during CD Heartbeat

condition. These outputs are open emitters; pulldown resistors to VEE are required.

When operating into a 78

Ω transmission line, these resistors should be 510Ω. In

Cheapernet applications, where the 78

Ω drop cable is not used, higher resistor

values (up to 1.5k) may be used to save power.

RX+*/RX-

O

Receive Output. Balanced differential line driver outputs from the Receiver. These

outputs also require 510

Ω pulldown resistors.

TX+*/TX-

I

Transmit Input. Balanced differential line receiver inputs to the Transmitter.

The

common mode voltage for these inputs is determined internally and must not be

externally established. Signals meeting Transmitter squelch requirements are

waveshaped and output at TXO.

HBE

I

Heartbeat Enable. This input enables CD Heartbeat when grounded or left opened,

disables it when connected to VEE.

RR+/RR-

I

External Resistor. A fixed 1 k

Ω 1% resistor connected between these pins

establishes internal operating currents.

RXI

I

Receive Input. Connects directly to the coaxial cable. Signals meeting Receiver

squelch requirements are equalized for inter-symbol distortion, amplified, and output

at RX+ and RX- pin.

TXO

O

Transmit Output. Connects via an isolation diode to the coaxial cable.

CDS

I

Collision Detect Sense. Ground sense connection for the collision detect circuit. This

pin should be connected separately to the shield to avoid ground drops from altering

the receive mode collision threshold.

GND

S

Positive Supply Pin.

VEE

S

Negative Supply Pins. These pins should be connected to a large metal frame area

on the PC board to handle heat dissipation, and bypassed to the GND pin with a 0.1

µF capacitor as close to the package as possible.

*IEEE names for CD± = CI±, RX± = DI±, TX± = DO±

Notes: Pin type: I-input; O-output; S-power supply