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

摘要

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 $0.18~mu{rm m}$ 2P4M EEPROM process. The die size of the proposed EEPROM IP is $0.12~{rm mm}^{2}$ . The read and write currents of the EEPROM IP are $1.18~mu{rm A}$ and $33~mu{rm A}$ respectively. Under a 110$^{circ}$ 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.