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Noise Suppression With Unsymmetrical Delay Element

IP.com Disclosure Number: IPCOM000102685D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 80K

Publishing Venue

IBM

Related People

Wong, C: AUTHOR

Abstract

This article describes an improvement in noise immunity and reliability of clock circuits gained by utilizing an unsymmetrical delay element as a pulse clipper to suppress noise spike disturbs in the system environment.

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This is the abbreviated version, containing approximately 66% of the total text.

Noise Suppression With Unsymmetrical Delay Element

       This article describes an improvement in noise immunity
and reliability of clock circuits gained by utilizing an
unsymmetrical delay element as a pulse clipper to suppress noise
spike disturbs in the system environment.

      Clock generation circuits designed to produce a clock pulse
from a single rising edge transition of the input clock signal are
sensitive to the disturbs of noise spikes in the system environment
that could lead to the generation of erroneous clock pulses.  The
disclosed solution to this problem utilizes a circuit with a
different turn-on (Ton) and turn-off (Toff) delay.  Any noise pulse
smaller than the difference between the Ton and Toff delay will not
propagate to the input of the clock generation circuits, as explained
hereinafter.

      Noise spikes should be clipped on-chip so that erroneous clock
pulses will not be accidentally activated. As shown in Fig. 1, the
clipping is accomplished by passing the external clock 1 through a
delay element 2, where the leading edge delay t1 is larger than the
trailing edge delay t2.  If t1 > t2, as indicated in the drawing, the
delay element 2 then becomes a pulse chopper; the external clock
pulse t0 is shrunk by (t1 - t2), and the leading edge of t0 is
delayed by t1.  Thus any noise spikes with durations under (t1 - t2)
are suppressed.

      This unsymmetrical delay can be easily instituted with a low
power inverter chain of curr...