An analog front-end circuit with dual-directional SCR ESD protection for UHF-band passive RFID tag

In this study, we demonstrate an analog front-end (AFE) circuit with ESD protection for a passive RFID tag at UHF-band (860~960 MHz) in a 0.18-μm CMOS technology. A dual-directional silicon-controlled-rectifier (dual-SCR) structure is proposed for the ESD protection under the large-signal operation at the RFID input. With the well-designed dual-SCR, a large trigger voltage (V
_T
) of ~16.9 V is obtained. The parasitic capacitance of the ESD block is only ~34 fF, which has virtually no impact on the core circuits at the frequency of interest. The measured ESD levels achieve 3.0-kV human-body-mode (HBM) and 200-V machine-mode (MM), respectively. The RF-DC rectifier in the RFID circuit can generate a stable power supply output about 1.2 V when the RF input power exceeds -7.5 dBm.