This paper presents a low power passive UHF RFID transponder IC, which is compatible with ISO/IEC 18000-6B Standard, operating at the 915 MHz ISM band with the total supply current consumption less than 10 μA. The fully integrated passive transponder, whose reading distance more than 3 m at 4 W (36 dBm) EIRP with an antenna gain less than 1.5 dBi, is powered by the received RF energy. There are no external components, except for the antenna. The transponder IC includes matching network, rectifier, regulator, power on reset circuit, local oscillator, bandgap reference, AM demodulator, backscatter, control logic and memory. The IC is fabricated using Chartered 0.35 μm two-poly four-metal CMOS process with Schottky diodes and EEPROM supported. The die size is 1.5 mm × 1.0 mm.