METHOD AND APPARATUS FOR BIPOLAR MEMORY WRITE-VERIFY

摘要

An advantageous write verify operation for bipolar memory devices is disclosed. The verify operation is performed under the same bias conditions as the write operation. Thus, the verify operation reduces disturb conditions caused when verify operation is performed in opposite bias to write operation. The advantageous write verify operation may be performed with control logic on source and bit lines. In another embodiment, the advantageous write operation is performed with mux coupled to control logic. The mux determines whether verify (0) or verify (1) operation should be performed based on data in a program latch. Moreover, the mux may select bias conditions for read operations based on a register bit. Trim circuits optionally provide guard banding and modify reference voltages for verify operations performed in opposite polarity to normal read operation.

主权项

1. A method for verifying data written to a bipolar memory device comprising:
writing a data bit into a memory cell, the memory cell comprising a bipolar memory element and a select transistor, wherein the memory cell is coupled to a bit line and a source line, wherein the writing step further comprises:
applying a first voltage differential across the source line and the bit line to supply a first current to write the data bit into the memory cell, the first voltage differential being of a first polarity if a logic high is to be written to the memory cell and a second polarity that is opposite the first polarity if a logic low is to be written to the memory cell; verifying the data bit written into the memory cell by applying a second voltage differential across the memory cell, wherein the verifying step further comprises:
applying the second voltage differential, the second voltage differential being the first polarity if a logic high was written in the writing step and being the second polarity if a logic low was written in the writing step.