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Redundant/Normal Clock Generation Redundant Wordline Addressing

IP.com Disclosure Number: IPCOM000099156D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

Jallice, DL: AUTHOR [+2]

Abstract

To implement wordline redundancy in a static RAM, must decide whether to address a normal wordline or a redundant wordline during the access cycle. A wordline is programmed using either electrically or laser-blown fuses.

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This is the abbreviated version, containing approximately 60% of the total text.

Redundant/Normal Clock Generation Redundant Wordline Addressing

       To implement wordline redundancy in a static RAM, must
decide whether to address a normal wordline or a redundant wordline
during the access cycle.  A wordline is programmed using either
electrically or laser-blown fuses.

      In a typical RAM, such as that shown in Fig. 1, there two
redundant wordlines and, therefore, two laser fuse  In the typical
scheme, the clock signal two parallel paths.  One path is through the
laser comparator.  The other is through the address T/C and the
normal wordline decoder.  A problem arises a redundant access occurs.
 Before access, during the cycle, CLK is low, precharging RWL0 and
RWL1 to 5 and disabling the T/C generator.  At access time, the is
driven to 5 volts and when the laser fuse output discharges, while
the other output stays 5 volts, matching the address.  Referring to
Fig. 2, if top laser fuse comparator has the matching address, RWL0
at 5 volts and RWL1 discharges to 0 volts.  Node 1 not change,
staying at zero volts.  There are two paths consider.  Path 1 starts
at CLK ---> CLK ---> 2 ---> Element Enable ---> WL000. 2 starts at
CLK ---> CLK ---> A0 ---> WL000.  The race caused by the two paths
can cause a glitch on a wordline.  This occurs because Path 2 is
faster than 1 and a normal access starts to happen until the Normal
Enable goes low, thereby disabling the access.  This glitch could
cause a normal wordline cell and a wordline...