Low-power Memory Circuits For Rfid Tags

RFID (Radio Frequency Identification) is a technology that uses RF signals to achieve contactless communication and Auto-Identification. As the carrier of information, embedded non-volatile memory is indispensable to the system of RFID tag. With the development of RFID technology, there occurs growing demands for those RFID tags which contain low cost, low power, large volume non-volatile memory. In accord with these requirements, in-depth researches of design solutions and techniques for NVM used in RFID tags are made in this dissertation.Firstly, the basic performance requirements for eNVM are discussed according to the the demands of UHF RFID tag systmen.Secondly, the storage mechanisms, cell structures and application charateristics of RRAM and EEPROM are studied in detail respectively. And a detailed comparison is carried out to illustrate the strength and weakness of RRAM and EEPROM, in accord with which, design solutions are discussed afterwards.Thirdly, A 64K bit low power Resistive Random Access Memory (RRAM) embedded in an RFID transponder is presented for the very first time. A high voltage regulator with surge current control is proposed to provide a fixed programming voltage for the programming operation and alleviate the startup surge issue as well. Also presented is a Sense Amplifier for 2T2R cell to achieve low power read-out. Critical circuits are analyzed and optimized in depth to meet the system specification. The measurement results indicate that the power consumption of the memory is 2.2μA and 18.5μA for a 640Kb/s read operation and a 5Kb/s write operation respectively. The whole chip is implemented in a 0.13μm standard CMOS process while the memory IP occupies 0.39mm2 die area.After that, in accord with the requirements of large volume EEPROM, the read-out circuits are greatly improved to ahieve low power low voltage read-out. Measurements show that EE chip can work under 0.7 V and cost less than 2μA.