Integrated circuit memory having a fuse detect circuit and method therefor

US 6,157,583 A
Filed: 03/02/1999
Issued: 12/05/2000
Est. Priority Date: 03/02/1999
Status: Expired due to Term

First Claim

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1. A fuse detect circuit, comprising:

a fuse state detect stage for providing an output signal of a first logic state in response to detecting a fuse is an open circuit, and for providing the output signal of a second logic state in response to detecting the fuse is a short circuit, wherein the fuse state detect stage limits a voltage drop across the fuse to an absolute value independent of a power supply voltage value applied to the fuse detect circuit; and

a latch stage, coupled to the fuse state detect stage, for latching a logic state of the output signal.

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Abstract

Fuses and detect circuits (124) in an integrated circuit memory (100) include a copper fuse (208) and a fuse state detect stage (202) for detecting the open circuit state or the closed circuit state of the fuse (208). The fuse detect circuit (124) provides an output signal corresponding to the state of the fuse and during detecting, limits a voltage drop across the fuse to an absolute value independent of a power supply voltage applied to the integrated circuit memory. The fuse detect circuit (124) operates at power up of the integrated circuit memory (100) and is disabled after the state of the fuse is detected and latched, and the power supply is sufficient for reliable operation of the integrated circuit memory (100). By limiting the voltage drop across a blown copper fuse (208), a potential electro-migration problem is reduced.

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20 Claims

1. A fuse detect circuit, comprising:
- a fuse state detect stage for providing an output signal of a first logic state in response to detecting a fuse is an open circuit, and for providing the output signal of a second logic state in response to detecting the fuse is a short circuit, wherein the fuse state detect stage limits a voltage drop across the fuse to an absolute value independent of a power supply voltage value applied to the fuse detect circuit; and
  
  a latch stage, coupled to the fuse state detect stage, for latching a logic state of the output signal.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- - 2. The fuse detect circuit of claim 1, wherein the fuse state detect stage detects the fuse is an open circuit or a short circuit during a power up sequence of an integrated circuit including the fuse detect circuit.
  - 3. The fuse detect circuit of claim 2, wherein the fuse state detect stage is disabled after detecting that the fuse is an open circuit or a short circuit.
  - 4. The fuse detect circuit of claim 3, wherein the fuse state detect stage is disabled in response to receiving a control signal indicating that the power supply voltage value is sufficient for reliable operation of the integrated circuit.
  - 5. The fuse detect circuit of claim 4, wherein the logic state of the output signal is latched before the fuse state detect stage is disabled.
  - 6. The fuse detect circuit of claim 1, wherein the fuse comprises copper.
  - 7. The fuse state detect circuit of claim 1, wherein the fuse detect stage comprises:
    - a first transistor having a first current electrode coupled to a first power supply voltage terminal, a second current electrode, and a control electrode coupled to the second current electrode of the first transistor;
      
      a second transistor having a first current electrode coupled to the first power supply voltage terminal, a second current electrode, and a control electrode coupled to the control electrode of the first transistor,a first resistor having a first terminal coupled to the second current electrode of the first transistor, and a second terminal, the first resistor having first resistance value;
      
      the fuse having a first terminal coupled to the first terminal of the first resistor and a second terminal coupled to the second terminal of the first resistor;
      
      a second resistor having a first terminal coupled to the second current electrode of the second transistor, and a second terminal, the second resistor having a second resistance value different from the first resistance value; and
      
      a third transistor having a first current electrode coupled to the second terminals of both of the first and second resistors, a control electrode for receiving a bias voltage, and a second current electrode coupled to a second power supply voltage terminal.
  - 8. The fuse detect circuit claim 7, wherein the first resistance value is larger than the second resistance value.
  - 9. The fuse detect circuit of claim 1, wherein the fuse detect circuit is one of a plurality of fuse detect currents used to store redundant element repair information in an integrated circuit memory.

10. An integrated circuit memory, comprising:
- a plurality of memory cells;
  
  a plurality of redundant memory cells;
  
  address decoding circuits, coupled to the plurality of memory cells and to the plurality of redundant memory cells, for selecting a memory cell in response to receiving an address; and
  
  a plurality of fuse detect circuits, coupled to the plurality of memory cells and to the plurality of redundant memory cells, for identifying a defective memory cell, and for identifying which of the plurality of redundant memory cells replaces the defective memory cell, a fuse detect circuit of the plurality of fuse detect circuits comprising;
  
  a fuse having an open circuit state and a short circuit state; and
  
  a circuit for detecting the open circuit state or the short circuit state of the fuse, and for providing a corresponding output signal, wherein during the detecting, the circuit limits a voltage drop across the fuse to an absolute value independent of a power supply voltage value applied to the integrated circuit memory.
- View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
- - 11. The integrated circuit memory of claim 10, wherein the circuit detects a state of the fuse during a power up sequence of the integrated circuit memory.
  - 12. The integrated circuit memory of claim 10, wherein the circuit is disabled in response to receiving a control signal indicating that the power supply voltage value is sufficient for reliable operation of the integrated circuit memory.
  - 13. The integrated circuit memory of claim 10, further comprising an amplifier stage, coupled to the circuit, for amplifying the output signal to produce an amplified output signal.
  - 14. The integrated circuit memory of claim 13, further comprising a latch, coupled to the circuit, for latching a state of the amplified output signal.
  - 15. The integrated circuit memory of claim 14, further comprising a control circuit, coupled to the circuit, for disabling the amplifier stage a predetermined time after the state of the amplified output signal is latched.
  - 16. The integrated circuit memory of claim 10, wherein the fuse comprises copper.
  - 17. The integrated circuit memory of claim 10, wherein the circuit comprises:
    - a first transistor having a first current electrode coupled to a first power supply voltage terminal, a second current electrode, and a control electrode coupled to the second current electrode of the first transistor;
      
      a second transistor having a first current electrode coupled to the first power supply voltage terminal, a second current electrode, and a control electrode coupled to the control electrode of the first transistor,a first resistor having a first terminal coupled to the second current electrode of the first transistor, and a second terminal, the first resistor having first resistance value;
      
      the fuse having a first terminal coupled to the first terminal of the first resistor and a second terminal coupled to the second terminal of the first resistor;
      
      a second resistor having a first terminal coupled to the second current electrode of the second transistor, and a second terminal, the second resistor having a second resistance value different from the first resistance value; and
      
      a third transistor having a first current electrode coupled to the second terminals of both of the first and second resistors, a control electrode for receiving a bias voltage, and a second current electrode coupled to a second power supply voltage terminal.
  - 18. The integrated circuit memory of claim 17, wherein the first resistance value is larger than the second resistance value.

19. In an integrated circuit memory, a method for implementing a fuse comprising the steps of:
- providing a fuse comprising copper, wherein the fuse, if intact, provides a first logic state and the fuse, if blown, provides a second logic state;
  
  detecting if the fuse is blown or intact using a fuse detect circuit;
  
  limiting a voltage drop across the fuse when the fuse is blown to an absolute value independent of a power supply voltage applied to the integrated circuit memory;
  
  storing a logic state of the fuse; and
  
  disabling the fuse detect circuit in response to the power supply voltage being sufficient for reliable operation of the integrated circuit memory.
- View Dependent Claims (20)
- - 20. The method of claim 19, wherein the step of detecting occurs during a power up sequence of the integrated circuit memory.

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Current Assignee
North Star Innovations Inc. (Wi-LAN Inc.)
Original Assignee
Motorola, Inc. (Motorola Solutions, Inc.)
Inventors
Starnes, Glenn E., Flannagan, Stephen T., Chang, Ray
Primary Examiner(s)
Nelms, David
Assistant Examiner(s)
Lam, David

Application Number

US09/261,876
Time in Patent Office

644 Days
Field of Search

365/200, 365/225.7, 365/230.08, 365/240, 365/96, 365/230.06, 327/526
US Class Current

365/200
CPC Class Codes

G06F 11/006   Identification G06F11/2289 ...

G11C 29/02   Detection or location of de...

G11C 29/44   Indication or identificatio...

Integrated circuit memory having a fuse detect circuit and method therefor

First Claim

19 Assignments

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Abstract

67 Citations

20 Claims

Specification

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Integrated circuit memory having a fuse detect circuit and method therefor

First Claim

19 Assignments

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0 Petitions

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Accused Products

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Abstract

67 Citations

20 Claims

Specification

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Others