AN1672 Datasheet, PDF (1/10 Pages) ON Semiconductor – The ECL Translator Guide

AN1672/D
The ECL Translator Guide
PECL • LVPECL • NECL • TTL •
LVTTL/LVCMOS • CMOS
Prepared by: Paul Shockman
ON Semiconductor
http://onsemi.com
APPLICATION NOTE
Objective
This application note is intended to provide the basic
device selection and connection information to enable signal
translation interface between ON Semiconductor’s ECL
logic operating in various supply modes This document also
provides information regarding translation between our
ECL devices and TTL (5 V), CMOS (5 V), or
LVTTL/LVCMOS (3.3 V) devices. For translation interface
with LVDS, see AN1568.
Translation to and from ECL technology is discussed in
three section divisions:
Section 1. Translation between differently supplied
ECL drivers and receivers
Section 2. Translation from different ECL operating
mode drivers to non ECL receivers
Section 3. Translation from non ECL drivers to
different ECL operating mode receivers
Proper translation occurs when the driver’s output logic
levels are within the spec limits of the receiver and are
recognized. Specific device data sheets should be consulted
for exact specifications and parameter limits.
Resources
IBIS and SPICE models may be found at
www.onsemi.com for most devices. General ECL
information, also online, may be consulted such as
AND8020, AND8066, and AND8072.
General Background
TTL and CMOS drivers generally source current (to the
receiver) in the HIGH state and sink current (from the
receiver) in the LOW state. In contrast, ECL drivers source
current in both HIGH and LOW states (to the receiver).
Receiver inputs do not require any “termination” although
any driver may or may not require termination
considerations. The driver termination considerations may
be located physically near or internal to a receiver.
TTL and CMOS devices will usually be operated across
a single positive power supply (V_CC or V_DD) and ground.
ECL devices may operate similarly across a single Positive
supply and V_EE (Ground) as Positive ECL (PECL) or Low
Voltage Positive ECL (LVPECL). Or traditionally, ECL
devices may span across Ground and a single negative
power supply, V_EE, as Negative ECL (NECL) or Low
Voltage Negative ECL (LVNECL). Any device may be
operated with all pins offset by a fixed voltage, but interface
with standard levels may require a translation device. A pure
ECL device might be operated in NECL, PECL, or LVPECL
mode by simply shifting all voltage levels. Of course, a
translator dedicated to a specific technology will expect only
fixed voltages and can’t usually operate in different, or
shifted voltage modes.
© Semiconductor Components Industries, LLC, 2004
1
November, 2004 − Rev. 9
Publication Order Number:
AN1672/D