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

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.