Flash memory reference current generating circuit and method

Abstract

A reference-current generation method for flash includes first and second memory arrays separated by a word-line switching circuit. A reference-current generation circuit includes rows of reference cells, the first row parallel with the other rows of the first memory array and having the same number of columns as the other rows thereof, and the second row parallel with the other rows of the second memory array and having the same number of columns as the other rows thereof. The first reference word line of the first row is disconnected with the second reference word line of the second row. After programming, the first row enables the first memory array to create the first reference current used while performing read operation for the second memory array, and the second row enables the second memory array to create the second reference current used while performing read operation for the first memory array.

Description

technical field [0001] The invention relates to the field of semiconductor integrated circuits, in particular to a reference current generating circuit of a flash memory (Flash). The invention also relates to a method for generating a reference current of a flash memory. Background technique [0002] In flash memory, floating gate transistors are mainly used to store information. Compared with conventional MOSFETs, floating gate transistors have one more floating gate in their gate structure. The states of gate transistors are different. For N-type devices, when electrons are written into the floating gate, that is, programming, the threshold voltage of the device will increase, and the channel will be cut off when no voltage is applied to the control gate; when the electrons in the floating gate are erased , the threshold voltage of the device will decrease, and the channel will be turned on when no voltage is applied to the control gate. [0003] Usually, a floating gate...

AI Technical Summary

Problems solved by technology

[0009] Usually, the reference cell 102 is the same as the memory cell, and the reference cell 102 is in an erased state, that is, the reference current is obtained with a saturated erased flash cell. Such a shortcoming is that since the reference cell 102 remains in an erased state, the However, the memory cells in the memory array will be constantly erased and written during use, so the memory cells in the memory array will change with the process, voltage and temperature, etc., and the reference cell 102 obviously cannot store these changes of the memory cells of the array. Tracking, so the reference unit 102 has the characteristics of I_V and temperature characteristics that cannot track the change of the storage unit, that is, the track tailbit, which will affect the speed and accuracy of the sense amplifier, thereby affecting the yield and performance of the entire Flash

Images