A Design Of Charge Pump Circuit Applied In RRAM

With the human society stepping into the era of artificial intelligence and big data,various types of data show an exponential growth trend.How to save the massive information reliably and at a high speed has become a key difficulty in the continuous development of cutting-edge science and technology.Although DRAM(Dynamic RandomAccess Memory)and Flash memory in the traditional sense can also expand a large capacity,they can not meet the storage requirements of the information age in terms of performance and cost in the context of the shrinking process nodes,and obviously do not have a strong competitive advantage in the fierce market competition.New memory has become the top priority of major scientific research institutions,especially Resistive RandomAccess Memory(RRAM)is considered to be one of the best solutions to the embedded memory application problems in advanced manufacturing processes,with the advantages of easy integration in the process,simple cell structure,high storage density and low power operation.Since the RRAM memory needs a voltage source that generates an internal low voltage,it is used to provide the BL bias voltage when set,the forming voltage and the SL bias voltage when reset.Also,a voltage source that generates an internal high voltage is needed to provide the BL voltage and SL voltage,and then pass the BL voltage and SL voltage into the Array.However,RRAM adopts a single external power supply,the external voltage is far from meeting the RRAM internal operation requirements,therefore,an excellent charge pump system has become an essential part of the entire RRAM memory.Firstly,this paper describes the working principle of RRAM and charge pump,and compares several charge pump structures.After comprehensively analyzing the advantages and disadvantages of several traditional charge pumps,according to the design requirements of RRAM,this topic selects a cross-coupling charge pump structure suitable for resistive memory RRAM.Combined with Edge Aligner to calibrate the clock edge on the charge pump circuit,it can effectively avoid the risk of capacitor leakage and short circuit caused by non-in-phase power switches conducting together at the same time.In the charge pump system of this project,a two-stage differential ring oscillator which meets the Barkhausen criterion is innovatively applied.In addition to the low power consumption advantage brought by fewer stages,the differential structure has a better ability to suppress the common mode noise and the power noise compared with the single-ended inverter structure.This paper also proposes a low-voltage and high-efficiency charge pump system architecture suitable for RRAM.Different from the traditional charge pump system,in addition to the positive charge pump module that generates internal high voltage,there is also a negative charge pump module that generates internal low voltage,which is an improvement based on the actual operation mode of RRAM.This project adopts the 28 nm HKC RRAM process of SMIC.Under this process,the negative pump voltage is-0.8 V and the output efficiency is greater than 70%.The voltage of the positive pump in the forming mode is 2.8 V,and the parallel mode enables the driving capacity to meet 1 mA under different conditions.The output voltage of the other operating modes is 2.6 V,the output efficiency is greater than 40%,and the voltage ripple is less than 200 mV.