Fast internal reference cell trimming for flash EEPROM memory
First Claim
1. A method for storing a charge on a memory device comprising the steps of:
- providing a first charging pulse to terminals of a memory device, the first charging pulse having a first charging voltage and a first duration such that the memory device stores close to a first amount of charge that is less than a target amount of charge;
testing the memory device to determine whether the memory device stores more than the first amount of charge;
if the first amount of charge is less than a first level, providing a second set of charging pulses to terminals of the memory device to charge the memory device close to the first level, each charging pulse of the second set of charging pulses having a second duration which is less than the first duration and a second charging voltage having a second amount of charge such that the memory device stores close to the first amount of charge;
testing the memory device to determine whether the memory device stores more than the first amount of charge after each charging pulse of the second set of charging pulses;
once the memory device has been determined as storing more than the first amount of charge, providing a third set of charging pulses to terminals of the memory device until the memory device stores the target amount of charge, each of the charging pulses of the third set of charging pulses having a third duration which is less than the second duration and a third charging voltage such that a third amount of charge furnished by each charging pulse of the third set of charging pulses is approximately equal to an allowable variation from the target amount of charge; and
testing the memory device to determine whether the memory device stores more than the target amount of charge after each charging pulse of the third set of charging pulses.
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Accused Products
Abstract
A method for storing a charge on memory devices which includes the steps of providing a first charging pulse to a memory device to charge the device to a first level less than a final level; testing the value of the charge to determine whether the charge is greater than the first level; if the value of the charge is less than the first level, providing a second set of charging pulses to the memory device, each of the pulses of the second set of pulses having a duration which is a fraction of the duration of the first pulse and a value sufficient to charge the device to the first level; testing the value of the charge to determine whether the charge is greater than the first level after each pulse of the second set of pulses; and once the charge has tested greater than the first level, providing a third set of charging pulses to terminals of the memory device, each of the pulses of the third set of pulses having a duration which is a fraction of the duration of the pulses of the second set of pulses and a value such that the charge furnished by each pulse is approximately equal to an allowable variation of the charge from the final value.
89 Citations
20 Claims
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1. A method for storing a charge on a memory device comprising the steps of:
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providing a first charging pulse to terminals of a memory device, the first charging pulse having a first charging voltage and a first duration such that the memory device stores close to a first amount of charge that is less than a target amount of charge;
testing the memory device to determine whether the memory device stores more than the first amount of charge;if the first amount of charge is less than a first level, providing a second set of charging pulses to terminals of the memory device to charge the memory device close to the first level, each charging pulse of the second set of charging pulses having a second duration which is less than the first duration and a second charging voltage having a second amount of charge such that the memory device stores close to the first amount of charge; testing the memory device to determine whether the memory device stores more than the first amount of charge after each charging pulse of the second set of charging pulses; once the memory device has been determined as storing more than the first amount of charge, providing a third set of charging pulses to terminals of the memory device until the memory device stores the target amount of charge, each of the charging pulses of the third set of charging pulses having a third duration which is less than the second duration and a third charging voltage such that a third amount of charge furnished by each charging pulse of the third set of charging pulses is approximately equal to an allowable variation from the target amount of charge; and testing the memory device to determine whether the memory device stores more than the target amount of charge after each charging pulse of the third set of charging pulses. - View Dependent Claims (2, 3, 4)
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5. A method for storing a charge on a flash EEPROM field effect memory device comprising the steps of:
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providing a first charging pulse to a gate terminal of the memory device while holding drain and source terminals constant, the first charging pulse having a first charging voltage and a first duration such that the memory device stores close to a first amount of charge that is less than a target amount of charge, the first amount of charge being sufficient to place the memory device in the saturation range of operation; testing the memory device to determine whether the memory device stores more than the first amount of charge; if the memory device stores less than the first amount of charge, providing a second set of charging pulses to the gate terminal of the memory device, each charging pulse of the second set of charging pulses having a second duration which is less than the first duration and a second charging voltage having a second amount of charge such that the memory device stores close to the first amount of charge; testing the memory device to determine whether the memory device stores more than the first amount of charge after each charging pulse of the second set of charging pulses; once the memory device has been determined as storing more than the first amount of charge, providing a third set of charging pulses to terminals of the memory device, each charging pulse of the third set of charging pulses having a third duration which is less that the second duration and a third charging voltage such that a third amount of charge furnished by each charging pulse of the third set of charging pulses is approximately equal to an allowable variation from the target amount of charge; and testing the memory device to determine whether the memory device stores more than the target amount of charge after each charging pulse of the third set of charging pulses. - View Dependent Claims (6, 7, 8)
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9. A method for programming a memory cell such that a memory device stores close to a target amount of charge, comprising the steps of:
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applying a first charging pulse to the memory device for a first duration such that the memory device stores a first amount of charge that is less than the target amount of charge; applying a second set of charging pulses to the memory device such that the memory device stores a second amount of charge that is less than the target amount of charge and greater than the first amount of charge, wherein each charging pulse of the second set of charging pulses is applied for a second duration that is less than the first duration; and applying a third set of charging pulses to the memory device such that the memory device stores a third amount of charge that is within an allowable variation of the target amount of charge, wherein each charging pulse of the third set of charging pulses is applied for a third duration that is less than the second duration. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A circuit for programming a memory cell such that a memory device stores close to a target amount of charge, comprising:
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means for applying a first charging pulse to the memory device for a first duration such that the memory device stores a first amount of charge that is less than the target amount of charge; means for applying a second set of charging pulses to the memory device such that the memory device stores a second amount of charge that is less than the target amount of charge and greater than the first amount of charge, wherein each charging pulse of the second set of charging pulses is applied for a second duration that is less than the first duration; and means for applying a third set of charging pulses to the memory device such that the memory device stores a third amount of charge that is within an allowable variation of the target amount of charge, wherein each charging pulse of the third set of charging pulses is applied for a third duration that is less than the second duration. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification