This paper presents proposed multi mode memory PUF design for high speed 5G IOT nodes. Since in conventional IOT nodes keys are used to be stored in non volatile memory, This will cause the side channel vulnerability and compromise the integrity. Silicon PUFs are used as feasible solution for this. However there is vulnerabilities in existed PUF architectures. To overcome these a new multi mode memory PUF was designed. This new PUF can be operated in two modes i.e Weak PUF(W) mode Strong(S) PUF mode. Authentication by Strong mode and weak Mode are discussed. The performance evolution metrics of proposed PUFs are close to ideal responses. The vulnerability analysis and possible side channel attacks such as data remanance attack and modeling attacks already performed in the existed memory PUFS were discussed and counter measures are used to design novel PUF of this work. The work is implemented on Artix-7 FPGA The authentication by S mode PUF and W mode PUF for IOT is implemented. The key generation by using W mode is implemented. The propose PUF has uniqueness is 49.96 %, uniformity is 49.87%, BER is 0.41