Claims
- 1. A method for testing a memory device, comprising the steps of:
writing test data to an array of cells of the memory device; driving a cell plate of the memory device during at least a portion of the test with a current level that is less than the current used during normal operation so as to amplify the affect of defective cells on the cell plate voltage.
- 2. The method of claim 1, wherein the step of driving the cell plate comprises the step of driving the cell plate with a reduced current level while a sense amplifier is active during the test mode.
- 3. The method of claim 1, wherein the step of driving the cell plate comprises the step of driving the cell plate voltage with a voltage generator wherein the width of the transistors in the voltage generator is less than the width of transistors used to generate the voltage on the cell plate during normal operation.
- 4. The method of claim 1, wherein the step of driving the cell plate comprises the step of driving the cell plate voltage through a larger resistance between a cell plate and a voltage generator for the cell plate while the sense amplifier is active.
- 5. A memory device, comprising:
an array of memory cells; addressing circuitry coupled to the array of memory cells that determines which cell is to be accessed; each cell including a capacitor for storing data, wherein the capacitors share a common cell plate; a voltage generator coupled to the cell plate to maintain the cell plate at a selected voltage; and wherein the voltage generator provides a first current level during at least a portion of a test mode and a second, different current level during normal operation.
- 6. The memory device of claim 5, wherein the voltage generator comprises a voltage generator that provides a current level during a portion of a test mode that is less than a current level provided during normal operation.
- 7. The memory device of claim 5, wherein the voltage generator comprises a variable resistance coupled between the output of the voltage generator and the cell plate such that the variable resistance is adjusted to limit the current to the cell plate during at least a portion of the test mode.
- 8. The memory device of claim 5, wherein the voltage generator comprises a variable resistance coupled between the output of the voltage generator and the cell plate such that the variable resistance is adjusted to limit the current to the cell plate when a sense amplifier is active during test mode.
- 9. The memory device of claim 5, wherein the voltage generator comprises first and second voltage generators formed with transistors of different widths, wherein the first voltage generator provides drive current to the cell plate during test mode and the second voltage generator provides drive current during normal operation.
- 10. A memory device, comprising:
a number of memory cells; each memory cell including a capacitor with one node coupled to a common cell plate; a number of intersecting word and digit lines, wherein memory cells are addressably coupled to the word and digit lines at the intersections; a voltage generator coupled to the cell plate that provides an adjustable current output to drive the cell plate.
- 11. The memory device of claim 10, wherein the voltage generator comprises an adjustable resistance for coupling the output of the voltage generator to the cell plate.
- 12. A method for generating a voltage, comprising the steps of:
receiving a control signal that indicates a desired current level output; generating a voltage with a voltage generator; and controlling the output current level of the voltage generator in response to the control signal.
- 13. The method of claim 12, wherein the step of controlling the output current level comprises the step of controlling a variable resistance at the output of the voltage generator.
- 14. The method of claim 13, wherein the step of controlling the output current level comprises the step of coupling voltage generators using transistors with varying sizes to output of the voltage generator based on the control signal.
- 15. A voltage generator with selectable current output, the voltage generator comprising:
an input that receives a control signal that indicates the desired current level from the voltage generator; means for generating a voltage; and means, coupled to the means for generating a voltage, for controlling the output current level of the voltage generator in response to the control signal.
- 16. The voltage generator of claim 15, wherein the means for controlling the output current level comprises a variable resistance coupled to the output of the means for generating a voltage.
- 17. The voltage generator of claim 15, wherein the means for generating a voltage comprises a first and second voltage generators, each fabricated with transistors with different widths, such that the first voltage generator provides a first output current level and the second voltage generator provides a second output current level.
- 18. A voltage generator coupled to a capacitor, the voltage generator comprising:
an input that receives a control signal that indicates a desired current level output; and circuitry adapted to:
generate a selected voltage; activate a first current path for an output of the voltage generator when a first current level is desired; and activate a second current path for the output of the voltage generator when a second current level is desired, such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 19. The voltage generator of claim 18, wherein the first and second current paths are distinct.
- 20. The voltage generator of claim 18, wherein the first current path includes the second current path.
- 21. The voltage generator of claim 18, wherein the circuitry adapted to activate a second current path comprises a number of transistors that are coupled in parallel to the output of the voltage generator such that turning on at least one of the transistors activates the second current path.
- 22. A voltage generator coupled to a capacitor, the voltage generator comprising:
at least a first integrated circuit transistor fabricated with an appropriate width to generate a normal drive current from a supply of electrical potential to operate a plurality of memory cells; and at least a second integrated circuit transistor fabricated with an appropriate width to generate a test drive current from the supply of electrical potential to test the memory cells for current leakage, such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 23. The voltage generator of claim 22, wherein the test drive current is lower than the normal drive current.
- 24. The integrated circuit voltage generator of claim 22, wherein:
the first integrated circuit transistor forms a part of a first voltage generator adapted for providing the normal drive current during normal operation; and the second integrated circuit transistor forms a part of a second voltage generator adapted for providing the test drive current during a test mode.
- 25. The integrated circuit voltage generator of claim 22, wherein:
the first integrated circuit transistor comprises a first pass through transistor adapted for providing the normal drive current during normal operation; and the second integrated circuit transistor comprises a second pass through transistor adapted for providing the test drive current during a test mode.
- 26. A voltage generator coupled to a capacitor, the voltage generator comprising:
a first voltage generator adapted for providing a normal drive current during normal operation; and a second voltage generator adapted for providing a test drive current during at least a portion of a test mode, such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 27. The voltage generator of claim 26, wherein the test drive current is lower than the normal drive current.
- 28. The voltage generator of claim 26, wherein:
the first voltage generator includes a first voltage divider and a first pass transistor coupled in series between an output of the first voltage divider and a generator output; and the second voltage generator includes a second voltage divider and a second pass transistor coupled in series between an output of the second voltage divider and the generator output.
- 29. The voltage generator of claim 26, wherein:
the first voltage generator includes:
a first voltage divider having a first n-channel transistor coupled to a first p-channel transistor in a voltage divider configuration to form a first voltage divider output, wherein the first n-channel transistor and the first p-channel are fabricated with an appropriate width to provide a desired current; and a first pass transistor coupled in series between the first voltage divider output and a generator output, wherein the normal drive current flows through an actuated first pass transistor; and the second voltage generator includes:
a second voltage divider having a second n-channel transistor coupled to a second p-channel transistor in a voltage divider configuration to form a second voltage divider output, wherein the second n-channel transistor and the second p-channel are fabricated with an appropriate width to provide a desired current; and a second pass transistor coupled in series between the second voltage divider output and the generator output, wherein the lower test drive current flows through an actuated second pass transistor.
- 30. The voltage generator of claim 26, wherein:
the normal drive current is sufficient to operate a plurality of memory cells; and the test drive current is limited to enhance testing of the memory cells for circuit leakage.
- 31. A voltage generator coupled to a capacitor, the voltage generator comprising:
a voltage divider having a voltage divider output connected to a capacitor; a first pass transistor coupled in series between the voltage divider output and a generator output, wherein the first pass transistor is fabricated with an appropriate width such that an actuated first pass transistor provides a normal drive current; and a second pass transistor coupled in series between the voltage divider output and the generator output, wherein the second pass transistor is fabricated with an appropriate width such that an actuated second pass transistor provides a lower test drive current such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 32. The voltage generator of claim 31, wherein the voltage divider comprises an n-channel transistor coupled to a p-channel transistor in a voltage divider configuration to form the voltage divider output.
- 33. The voltage generator of claim 31, wherein:
the normal drive current is sufficient to operate a plurality of memory cells; and the test drive current is limited to enhance testing of the memory cells for circuit leakage.
- 34. A voltage generator coupled to a capacitor, the voltage generator comprising:
a source of electric potential; a first pass transistor coupled in series between the source of electric potential and a generator output, wherein the first pass transistor is fabricated with an appropriate width such that an actuated first pass transistor provides a normal drive current; and a second pass transistor coupled in series between the source of electric potential and the generator output, wherein the second pass transistor is fabricated with an appropriate width such that an actuated second pass transistor provides a lower test drive current, and wherein a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 35. The voltage generator of claim 34, wherein the source of electrical potential is a voltage divider coupled to a power supply connection.
- 36. The voltage generator of claim 34, wherein the source of electrical potential is a voltage divider, comprising an n-channel transistor coupled to a p-channel transistor in a voltage divider configuration to form a voltage divider output.
- 37. The voltage generator of claim 34, wherein:
the normal drive current is sufficient to operate a plurality of memory cells; and the test drive current is limited to enhance testing of the memory cells for circuit leakage.
- 38. A voltage generator coupled to a capacitor, the voltage generator comprising:
a power supply connection; a control signal input; a generator output connected to the capacitor; a first generator circuit operably connected to the power supply connection and to the control signal input, wherein the first generator circuit produces a normal drive current at the generator output upon receiving a normal control signal at the control signal input; and a second generator circuit operably connected to the power supply connection and to the control signal input, wherein the second generator circuit produces a test drive current at the generator output upon receiving a test control signal at the control signal input such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 39. The voltage generator of claim 38, wherein:
the first generator circuit includes:
a first voltage divider having a first voltage divider output; and a first pass through transistor coupled in series between the first voltage divider output and the generator output, wherein a gate of the first pass through transistor is coupled to the control signal input such that the normal control signal actuates the first pass through transistor; and the second generator includes:
a second voltage divider having a second voltage divider output; and a second pass through transistor coupled in series between the second voltage divider output and the generator output, wherein a gate of the second pass through transistor is coupled to the control signal input such that the normal control signal actuates the second pass through transistor.
- 40. The voltage generator of claim 38, wherein:
the normal drive current is sufficient to operate a plurality of memory cells; and the test drive current is limited to enhance testing of the memory cells for circuit leakage.
- 41. The voltage generator of claim 38, wherein the test drive current is lower than the normal drive current.
- 42. The voltage generator of claim 38, wherein:
the normal drive current is sufficient to operate a plurality of memory cells; and the test drive current is limited to enhance testing of the memory cells for circuit leakage.
- 43. A voltage generator coupled to a capacitor, the voltage generator comprising:
a power supply connection; a control signal input; a generator output connected to the capacitor; a first voltage divider coupled to the power supply connection, wherein the first voltage divider has a first voltage divider output; a first pass through transistor coupled in series between the first voltage divider output and the generator output, wherein:
a gate of the first pass through transistor is coupled to the control signal input such that a normal control signal at the control signal input actuates the first pass through transistor; and an actuated first pass through transistor provides a normal drive current at the generator output; a second voltage divider coupled to the power supply connection, wherein the second voltage divider has a second voltage divider output; and a second pass through transistor coupled in series between the second voltage divider output and the generator output, wherein:
a gate of the second pass through transistor is coupled to the control signal input such that a test control signal at the control signal input actuates the second pass through transistor; and an actuated second pass through transistor provides a test drive current at the generator output such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 44. The voltage generator of claim 43, wherein both the first voltage divider and the second voltage divider have an n-channel transistor coupled to a p-channel transistor in a voltage divider configuration.
- 45. The voltage generator of claim 43, wherein:
both the first voltage divider and the second voltage divider have an n-channel transistor coupled to a p-channel transistor in a voltage divider configuration; the transistors of the first voltage divider are fabricated with an appropriate width to generate the normal drive current; and the transistors of the second voltage divider are fabricated with an appropriate width to generate the test drive current.
- 46. The voltage generator of claim 43, wherein the generator output is coupled to a common node for a plurality of memory cells.
- 47. The voltage generator of claim 43, wherein the test drive current is lower than the normal drive current.
- 48. A voltage generator coupled to a capacitor, the voltage generator comprising:
a power supply connection; a control signal input; a generator output connected to the capacitor; a voltage divider having a voltage divider output; a first pass transistor coupled in series between the voltage divider output and the generator output, wherein the first pass transistor is fabricated with an appropriate width such that an actuated first pass transistor provides a normal drive current; and a second pass transistor coupled in series between the voltage divider output and the generator output, wherein the second pass transistor is fabricated with an appropriate width such that an actuated second pass transistor provides a test drive current such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 49. The voltage generator of claim 48, wherein the voltage divider comprises an n-channel transistor coupled to a p-channel transistor in a voltage divider configuration to form the voltage divider output.
- 50. The voltage generator of claim 48, wherein the voltage divider has an n-channel transistor coupled to a p-channel transistor in a voltage divider configuration.
- 51. The voltage generator of claim 48, wherein the generator output is coupled to a common node for a plurality of memory cells.
- 52. The voltage generator of claim 48, wherein the test drive current is lower than the normal drive current.
- 53. The voltage generator of claim 48, wherein:
the normal drive current is sufficient to operate a plurality of memory cells; and the test drive current is limited to enhance testing of the memory cells for circuit leakage.
- 54. A voltage generator coupled to a capacitor, the voltage generator comprising:
a control signal input; a generator output connected to the capacitor; a source of electric potential; a first pass transistor coupled in series between the source of electric potential and the generator output, wherein the first pass transistor is fabricated with an appropriate width such that an actuated first pass transistor provides a normal drive current; and a second pass transistor coupled in series between the source of electric potential and the generator output, wherein the second pass transistor is fabricated with an appropriate width such that an actuated second pass transistor provides a test drive current such that a voltage on the capacitor rapidly changes when a current leakage path is present due to a defect in the capacitor.
- 55. The voltage generator of claim 54, wherein the source of electrical potential is a voltage divider coupled to a power supply connection.
Parent Case Info
[0001] This application is a Divisional of U.S. application Ser. No. 09/640,611, filed Aug. 17, 2000, which is a Divisional of U.S. application Ser. No. 09/360,952, filed Jul. 27, 1999, now U.S. Pat. No. 6,134,162, which is a Continuation of U.S. application Ser. No. 09/031,973, filed Feb. 26, 1998, now U.S. Pat. No. 5,943,276, which is a Continuation of U.S. application Ser. No. 08/851,416, filed May 5, 1997, now U.S. Pat. No. 5,822,258, all of which are incorporated herewith.
Divisions (2)
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Number |
Date |
Country |
Parent |
09640611 |
Aug 2000 |
US |
Child |
10099220 |
Mar 2002 |
US |
Parent |
09360952 |
Jul 1999 |
US |
Child |
09640611 |
Aug 2000 |
US |
Continuations (2)
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Number |
Date |
Country |
Parent |
09031973 |
Feb 1998 |
US |
Child |
09360952 |
Jul 1999 |
US |
Parent |
08851416 |
May 1997 |
US |
Child |
09031973 |
Feb 1998 |
US |