應用於小電流非揮發性記憶體之抑制飄移偏差電流感測放大器

現今的系統單晶片中，非揮發性記憶體扮演了不可或缺的角色，儲存其他周邊單元之資料並提供重複讀取。隨著製程的進步，單位面積下所能夠放置的記憶體容量也越來越大，但相對的不論是非或閘型快閃記憶體、非及閘型快閃記憶體或是一次性寫入記憶體，其記憶體單元之表示電流也越來越小，產生了讀取困難。此外製程的演進也顯現了電晶體不匹配的現象，而使得小電流的讀取更加困難。因此，為了能夠仍使用電流讀取的方式來得到高速操作下，我們提出了一個新的電流感測放大器並且具有壓低電晶體不匹配誤差的效果。在所提出的電流感測放大器中，我們對要比較的電流進行採樣放大。其中採樣過程使得比較電流不需經過電晶體臨界電壓的電流電壓轉換而失真。放大部分則利用電流充電之方式來達到放大效果，以避免因電晶體臨界電壓的不同而產生讀取能力不匹配的現象。此外我們也採用了對稱陣列來達到匹配的環境以及平均電流的效果來消除參考電流源的變異度。最後我們以提出的新電流感測放大器，以九十奈米互補金氧半製程技術建構出一個由五百一十二千字元(512Kb)所組成的一次性寫入記憶體電路。量測顯示以此種電流感測放大器之電路，在供應電壓為一點二伏情況下，以及參考電流源為一百奈安培下，其最小可讀取電流為一百四十奈安培。

關鍵字

非揮發性記憶體；電流感測放大器；抑制飄移偏差

並列摘要

In today’s SOC chip, non-volatile memory plays an important role to store the data from other peripheral unit and can read out repeatable. With the technology shrink, the cell array in same area is larger and larger. However, the cell current is also decreased not only NOR type flash but also NAND type flash or OTP and difficult to read. With the nanometer technology, the transistor threshold voltage mismatch gets more pronounced and making the sensing failure easily. To solve this problem, we propose a new current mode sense amplifier with offset suppress scheme. In this design, we sample the input current and amplify the difference without regard the threshold voltage variation. Furthermore, we use symmetric array to reduce mismatch between cell side and reference side and use average technique to reduce the variation on reference current due to PVT variation. We apply our design in 90nm CMOS technology within 512Kb OTP. The experiment result shows that, the minimum cell current can be read in 100nA reference current condition and power supply 1.2V is 140nA.

並列關鍵字

Non-Volatil memory ； Current sense amplifier ； Offset free

參考文獻

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國際替代計量

應用於小電流非揮發性記憶體之抑制飄移偏差電流感測放大器

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