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Flash EEprom system with cell by cell programming verification

DC
  • US 5,991,517 A
  • Filed: 12/20/1996
  • Issued: 11/23/1999
  • Est. Priority Date: 04/13/1989
  • Status: Expired due to Fees
First Claim
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1. A method of operating an EEprom system having memory cells that individually include an electrically floating gate carrying a charge level that is alterable in response to appropriate voltage conditions being applied to the cell in order to set a variable threshold level thereof into a range that is determinable by reading the cell, said method comprising:

  • applying said appropriate voltage conditions in parallel to a plurality of said memory cells, thereby to alter the charge levels on the floating gates of said plurality of memory cells,determining the threshold level ranges in which individual ones of said plurality of memory cells lie, andterminating said application of appropriate voltage conditions to individual ones of said plurality of memory cells upon their being determined to have reached desired threshold level ranges while continuing to apply said appropriate voltage conditions to others of said plurality of cells until all of the plurality of cells are determined to have reached their desired threshold level ranges.

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