Memory expansion scheme of psram pseudo static memory EMI132LA16LM-70I

PSRAM is also called pseudo-static random access memory,which presents an SRAM-like interface protocol:as long as the address is given and the read or write command is initiated,data access can be completed directly,and there is no need to rely on the memory controller for periodic refresh operation like DRAM.This makes PSRAM quite simple in hardware connection and control logic.
 

Take EMI132LA16LM-70I introduced by Yingshang on behalf of Weiling Chuangxin EMI as an example.This psram chip adopts 2M x 16 organizational structure,with a total capacity of 32Mb,a stable working voltage of 2.7V~3.3V,a reading and writing speed of 60~70ns,and a package form of 48-ball BGA,which is very suitable for external expansion memory of MCU.Its internal memory cell adopts DRAM architecture-that is,1T1C(one transistor plus one capacitor)constitutes a memory cell,while the traditional SRAM needs six transistors to achieve the same function.It is this mixed design of"DRAM core+SRAM interface"that makes PSRAM pseudo static memory inherit the advantages of high density and low cost of DRAM,while retaining the convenience of SRAM.
 

PSRAM advantage

First,high density and low cost.Because of the cell structure of DRAM,under the same chip area,PSRAM can achieve much larger storage capacity than SRAM,and the cost per unit capacity is obviously lower than that of SRAM with the same specification.
 

Second,the interface is simple and easy to integrate.The parallel interface of PSRAM is almost completely compatible with SRAM,and no additional DRAM controller is needed.For MCU,DSP or SoC accustomed to using standard parallel ports,it can be used directly like external SRAM,which greatly reduces the complexity of hardware design and software driver.
 

Third,the standby power consumption control is excellent.Self-refresh circuit is integrated in PSRAM.When the main processor enters sleep or low-power mode,PSRAM can keep data from being lost,and the overall power consumption of the system is significantly reduced.This feature is particularly important in battery-powered portable devices,sensor nodes of the Internet of Things and other scenarios.