System that facilitates reading multi-level data in non-volatile memory
View Patent ↗The present invention pertains to a system that facilitates a determination of the level of a bit in a dual sided ONO flash memory cell where each of the bits of the dual sided ONO flash memory cell can be programmed to multiple levels. One or more aspects of the present invention take into consideration the affect that the level of charge on one bit can have on the other bit, otherwise known as complimentary bit disturb. A metric known as transconductance is utilized in making the bit level determination to provide a greater degree of resolution and accuracy. In this manner, determining the bit level in accordance with one or more aspects of the present invention mitigates false or erroneous reads.
1. An architecture adapted to determine a level of a bit in a multi-level memory cell, comprising:
a current conversion component operative to convert a measured current from the cell into a corresponding analog voltage;
an analog to digital (A/D) converter operative to convert the analog voltage into a digital value; and
a data processor adapted to determine the level of the bit from the digital value, wherein the data processor is implemented as a field programmable gate array (FPGA), and wherein the FPGA comprises:
a data vector processor operative to facilitate a determination of the level of the bit by comparing the digital value to predetermined criteria.
2. The architecture of claim 1 , wherein the FPGA further comprises:
a FLASH memory interface operatively coupled to the data vector processor and adapted to facilitate storage of the bit level in external FLASH memory via a FLASH signal indicative of the bit level.
3. The architecture of claim 1 , wherein the A/D converter is an 8 bit converter.
4. The architecture of claim 1 , wherein the FPGA further comprises:
report logic operatively coupled to the data vector processor and adapted to send a tester report signal to an external tester indicative of the bit level.
5. The architecture of claim 4 , wherein the FPGA facilitates a determination of a gate voltage Vgate 2 that produces the measured current when applied to a gate of the cell.
6. The architecture of claim 5 , wherein the FPGA causes an initial voltage to be applied to the gate of the cell and then iteratively increased until the gate voltage Vgate 2 is determined.
7. The architecture of claim 6 , wherein the data vector processor facilitates a determination that Vgate 2 is equal to the most recently applied voltage when a current resulting from the most recently applied voltage satisfies one or more predetermined criteria.
8. The architecture of claim 6 , wherein the initial gate voltage is increased by about 100 millivolts until the gate voltage Vgate 2 is determined.
9. The architecture of claim 6 , wherein the FPGA further comprises:
a tester command interpreter adapted to receive a tester command signal from the external tester indicative of the initial voltage to be applied to the gate of the cell.
10. The architecture of claim 9 , wherein the iterative increase of the gate voltage is controlled by a tester command signal from the external tester.
11. The architecture of claim 1 , wherein the current conversion component comprises:
a transimpedance amplifier operative to convert the measured current into a voltage value that is also elevated (offset) as a function of a voltage applied to the cell in order to produce the current that is measured; and
a differential amplifier downstream of the transimpedance amplifier operative to match the elevated (offset) voltage value to requirements posed by other downstream components in the channel, as well as to further amplify the signal.
12. The architecture of claim 11 , further comprising:
a clock generator operatively coupled to the FPGA to facilitate clocking data through the architecture.
13. The architecture of claim 1 , further comprising:
a relay operative to selectively couple the measured current to the current conversion component.
14. The architecture of claim 13 , further comprising:
a selectively energizeable coil operatively associated with the relay to control activation of the relay.
15. The architecture of claim 14 , wherein the coil is controlled by the FPGA.