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Directly Addressable Redundant Word Line

IP.com Disclosure Number: IPCOM000060137D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Chu, JL: AUTHOR [+2]

Abstract

A directly addressable redundant word line with automatic deselect is described for use in bipolar memory. By blowing fuses corresponding to a defective or bad word line address, the redundant word line is substituted for the bad word line without: access degradation, race conditions, extra module pins, or multiple substrate part numbers. The diagram shows the circuitry used to implement the redundant word line WR. Transistor TR controls the redundant word driver, and the compare and steering functions are provided by the combination of eight diodes 18 and eight fuses 20. Operation is illustrated in the following example: 1. With no fuses blown, the redundant line will not be selected since both the true and complement outputs of the address buffers are connected to the decoding diodes 18. 2.

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Directly Addressable Redundant Word Line

A directly addressable redundant word line with automatic deselect is described for use in bipolar memory. By blowing fuses corresponding to a defective or bad word line address, the redundant word line is substituted for the bad word line without: access degradation, race conditions, extra module pins, or multiple substrate part numbers. The diagram shows the circuitry used to implement the redundant word line WR. Transistor TR controls the redundant word driver, and the compare and steering functions are provided by the combination of eight diodes 18 and eight fuses 20. Operation is illustrated in the following example: 1. With no fuses blown, the redundant line will not be selected since both the true and complement outputs of the address buffers are connected to the decoding diodes 18. 2. Once a defective word line and its address is determined (for instance, 1011 with 1 being high), the corresponding fuses are blown as indicated in the diagram to enable the redundant word line WR. 3. With any address other than 1011, one of the four transistors (TA, TB, TC, or TD) will conduct, keeping the redundant word line off. With address 1011, transistor TR will conduct, turning the redundant word line on and transistors TA through TD are off, preventing all other word lines from turning on. The value of resistor R is chosen such that a sufficient voltage drop is provided to guarantee the operation of the current switch composed...