An Ultra Low-Power Solution for EEPROM in Passive UHF RFID Tag IC With a Novel Read Circuit and a Time-Divided Charge Pump

Abstract

A dual power supply ultra low-power 1 kbits EEPROM for passive UHF RFID is presented. The read power source is 1 V, while the write power source is 1.65 V, which is only activated in the write mode. To reduce the power of the read circuit without impacting the performance, a pre-charge scheme, a feedback scheme and a self-detect circuit, combined with a special read time sequence are adopted. A time-divided charge pump is proposed to reduce the current surge of the charge pump at the startup phase. The EEPROM IP has been fabricated in a SMIC 0.18 μm 2P4M EEPROM process. The die size of the proposed EEPROM IP is 0.12 mm2. The read and write currents of the EEPROM IP are 1.18 μA and 33 μA respectively. Under a 110 temperature variation, the power variation of the read operation is 15%. The EEPROM IP is then verified in a full UHF RFID chip. Tested by a commercial reader at 4 W EIRP, the maximum read and write communication ranges are 6 m and 3 m respectively. The measured voltage drop of the output of rectifier Vrect caused by the current surge of the charge pump is smaller than 50 mV.