MC100EP223 Datasheet, PDF (1/8 Pages) Motorola, Inc – Low-Voltage 1:22 Differential PECL/HSTL Clock Driver

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Low-Voltage 1:22 Differential
PECL/HSTL Clock Driver
MC100EP223
The MC100EP223 is a low skew 1–to–22 differential driver, designed
with clock distribution in mind. It accepts two clock sources into an input
multiplexer. The selected signal is fanned out to 22 identical differential
outputs.
• 200ps Part–to–Part Skew
• 50ps Output–to–Output Skew
• Differential Design
• Open Emitter HSTL Compatible Outputs
• 3.3V VCC
• Both PECL and HSTL Inputs
• 75kΩ Input Pulldown Resistors
• Thermally Enhanced 64 lead Exposed Pad LQFP
LOW–VOLTAGE
1:22 DIFFERENTIAL
PECL/HSTL CLOCK DRIVER
The EP223 is specifically designed, modeled and produced with low
skew as the key goal. Optimal design and layout serve to minimize
gate–to–gate skew within a device, and empirical modeling is used to
determine process control limits that ensure consistent tpd distributions
from lot to lot. The net result is a dependable, guaranteed low skew
device.
TC SUFFIX
64–LEAD LQFP PACKAGE
CASE 840K–01
The EP223 HSTL outputs are not realized in the conventional
manner. To minimize part–to–part and output–to–output skew, the HSTL
compatible output levels are generated with an open emitter
architecture. The outputs are pulled down with 50Ω to ground, rather
than the typical 50Ω to VDDQ pullup of a “standard” HSTL output.
Because the HSTL outputs are pulled to ground, the EP223 does not
utilize the VDDQ supply of the HSTL standard. The output levels are
derived from VCC.
In the case of an asynchronous control, there is a chance of
generating a ‘runt’ clock pulse when the device is enabled/disabled. To
avoid this, the output enable (OE) is synchronous so that the outputs
will only be enabled/disabled when they are already in the LOW state.
To ensure that the tight skew specification is met it is necessary that both sides of the differential output are terminated into
50Ω, even if only one side is being used. In most applications, all 22 differential pairs will be used and therefore terminated. In
the case where fewer than 22 pairs are used, it is necessary to terminate at least the output pairs on the same package side as
the pair(s) being used on that side, in order to maintain minimum skew. Failure to do this will result in small degradations of
propagation delay (on the order of 10–20ps) of the output(s) being used which, while not being catastrophic to most designs, will
mean a loss of skew margin.
This document contains information on a product under development. Motorola reserves the right to change or
discontinue this product without notice.
03/01
© Motorola, Inc. 2001
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