Redundancy circuit for high speed EPROM and flash memory devices

• US 5,200,922 A
• Filed: 10/24/1990
• Issued: 04/06/1993
• Est. Priority Date: 10/24/1990
• Status: Expired due to Term

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: ON Semiconductor Corporation
• Inventors: Rao, Kameswara K.
• Primary Examiner(s): Popek, Joseph A.
• Application Number:
  US07/602,999
• Time in Patent Office: 895 Days
• Field of Search: 365/200, 365/210, 365/230.06, 365/225.7, 371/10.1, 371/10.3
• US Class Current: 365/185.09
• CPC Class Codes: G11C 16/08 Address circuits; Decoders; Word-line control circuits
• CPC Class Codes: G11C 29/789 using non-volatile cells or latches
• CPC Class Codes: G11C 29/83 with reduced power consumption

Abstract

A redundancy control circuit enables the redundancy of a row or a column in a memory array such that no degradation in access time occurs. The redundancy circuit is further configured such that negligible power is consumed by the circuit during both a standby mode and a redundancy enable mode.

Claims

1. A control circuit for enabling a reading operation of a plurality of redundant cells in a memory circuit, the memory circuit having an array of memory cells and a memory array decoding circuit coupled to said memory array and connectable to a plurality of addressing lines, said control circuit comprising:

a redundant cell decoding circuit coupled to said plurality of redundant cells for providing a select signal to said redundant cells;

an address select circuit coupled to said redundant cell decoding circuit and connectable to said plurality of addressing lines, said address select circuit including a first means for programming said address select circuit to provide an address select signal to said redundant cell decoding circuit in response to an address signal at said addressing lines;

an enable-disable circuit coupled to said redundant cell decoding circuit having a second means for programming said enable-disable circuit to provide an enable signal to said redundant cell decoding circuit;

wherein said first means for programming said address select circuit is a first programmable fuse circuit and wherein said means for programming said enable-disable circuit is a second programmable fuse circuit and wherein each of said first and second programmable fuse circuits include;

a first programmable element;

an enable input line coupled to said first programmable element for receiving a chip select pulse; and

an output line coupled to said first programmable element;

wherein a first voltage level is latched at said output line when said first programmable element is programmed in a first state, and wherein a second voltage level is latched at said output lien when said first programmable element is programmed in a second state.

2. The control circuit as recited in claim 1 further comprising a disable decoder circuit for disabling said memory array decoding circuit when said redundant cell decoding circuit provides said select signal to said redundant cells.

3. The control circuit as recited in claim 1 wherein said first voltage level is latched at said output line before and after an assertion of said chip select pulse.

4. The memory circuit according to claim 1 wherein the access time of said memory when reading from a redundant memory cell is less than or equal to the access time of said memory when reading from a non-redundant memory cell.