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Power Supply and Temperature-Compensated Emitter-Coupled Logic to Transistor-Transistor Logic Output Driver

IP.com Disclosure Number: IPCOM000111364D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

Freitag, LW: AUTHOR [+3]

Abstract

A power supply and temperature-compensated Emitter-Coupled Logic (ECL) to Transistor-Transistor Logic (TTL) output driver is disclosed. The driver converts a differential ECL input signal to a signal-ended TTL output signal. It uses two power supply and temperature compensating current sources in its level-shifting input stage. The output stage uses a two-transistor totem-pole configuration with Baker clamps to prevent saturation of the two transistors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Power Supply and Temperature-Compensated Emitter-Coupled Logic to
Transistor-Transistor Logic Output Driver

      A power supply and temperature-compensated Emitter-Coupled
Logic (ECL) to Transistor-Transistor Logic (TTL) output driver is
disclosed.  The driver converts a differential ECL input signal to a
signal-ended TTL output signal.  It uses two power supply and
temperature compensating current sources in its level-shifting input
stage.  The output stage uses a two-transistor totem-pole
configuration with Baker clamps to prevent saturation of the two
transistors.

      ECL-to-TTL converters are used to convert differential ECL
signals to single-ended TTL signals.  When the ECL input is in its
high state, the TTL output should also be in its high state.
Conversely, when the ECL input is in its low state, the TTL output
should be in its low state.  Power supply voltage (P5V) and
temperature variations, however, may force the TTL output into an
incorrect state.

      The Figure shows the power supply and temperature-compensated
ECL-to-TTL output driver.  It consists of a power supply and
temperature-compensated level-shifting input stage and a high-speed
output stage.  The differential ECL inputs are labeled C0 and C1, and
the single-ended TTL output is labeled 10.  This driver uses a power
supply of 5V +-  10%.

      The voltage and temperature-compensated input stage contains
two compensation circuits.  The first compensation circuit is a
current source made of transistors Q9, Q11, and Q12, diodes D4 and
D5, and resistors R14, R16, R17, and R18.  It provides a temperature
and power supply dependent current through resistor R3.  At nominal
voltage and temperature, this circuit provides a voltage drop of 1.0
V across R3.  When the power supply increases or decreases, V[R3]
correspondingly increases or decreases to partially absorb the power
supply variation.  When the input is in its high state, the remainder
of the power supply variation is absorbed by the voltage drop across
R1.  When the input is in its low state, only 56% of the power supply
variation is absorbed by V[R3] This does not create a problem,
because the voltage at node 6 remains high enough to turn on Q6 and
Q8 even when the power supply  is 4.5V.  V[R3]  also increases or
decreases in response to an...