AN-784 Datasheet, PDF (1/6 Pages) Fairchild Semiconductor – F100K ECL Dual Rail Translators

AN-784
Fairchild Semiconductor
Application Note
June 1991
Revised February 2004
F100K ECL Dual Rail Translators
INTRODUCTION
The complex electronic systems being designed today
often require mixed technologies to incorporate the most
efficient balance of performance, speed, power, and cost.
In order for one technology to communicate with the other,
an interface is needed. One of the most common mix of
technologies seen today is high speed ECL with the slower,
but very popular TTL and CMOS. To make this interface as
quick and clean as possible, level translators are used.
This applications note will discuss ECL to TTL and TTL to
ECL level translators available from Fairchild Semiconduc-
tor’s F100K ECL 300 Series product line. Focus will be on
Dual Rail Translators (translators which require both ECL
and TTL power supplies for normal operation), their differ-
entiating features and possible uses.
TRANSLATOR SELECTION
Fairchild Semiconductor offers translators of all different
types. Table 1 shows the TTL to ECL and ECL to TTL
translators that are presently available. The first 300 Series
translators designed were the 100324 and 100325. With
these devices, unidirectional translation is possible in either
direction (TTL to ECL with the 100324, ECL to TTL with the
100325). As systems and data widths become larger, more
bits need to be translated. This need was satisfied with the
introduction of 8- and 9-bit translators. The 8-bit translator
(100329) also offer bidirectional translation functionality for
applications which require two way communication. In
many cases, communication over significant distances is
needed in noisy environments. In applications where high
output drive is needed after an ECL to TTL translation the
9-bit 100395 can be used. The 64 mA I_OL output current
capability is ideal for driving long lines and achieving faster
switching times by discharging the line it is tied to faster
when in the LOW output state. These outputs are also
capable of driving higher fanouts than the lower output cur-
rent devices.
If the designer only has a +5V supply available (i.e., An
additional ECL supply cannot be used), single rail transla-
tors can be used. For more information on single rail trans-
lation refer to applications note AN-780 “Operating ECL
From a Single Positive Supply”.
TABLE 1. 300 Series Dual Rail Translators
Features
Data Bits
ECL to TTL
TTL to ECL
Latched
Registered
ECL Differential
ECL Drive (Ohms)
ECL Cutoff
TTL Drive I_OL/I_OH (mA)
TTL 3-STATE
ECL Control Pins
TTL Control Pins
TPD ECL to TTL (ns Max)
TPD TTL to ECL (ns Max)
I_EE (mA Max)
I_CC (mA Max)
Note 1: V_BB output available for 100325
100324
6
X
OUT
50
X
3.0
−70
38
100325
6
X
IN (Note 1)
20/−2
4.8
−37
65
100329
8
X
X
X
50
X
24/−3
X
X
7.7
3.9
−199
74
100395
9
X
X
64/−15
X
X
6.4
−67
65
MECL is a trademark of Motorola, Inc.
© 2004 Fairchild Semiconductor Corporation AN010938
www.fairchildsemi.com