A Threshold Voltage Generator Circuit with Automatic Refresh and Dynamic Updating for Ultra-Low-Power Continuous-Time Comparators

A Threshold Voltage Generator (TVG) circuit for continuous-time comparators is presented. It may be used in ULP IoT systems requiring nanoWatt power consumption, kbps bitrates and the reception of packets with lengths up to hundreds of bits. The circuit is based on a switched capacitor technique to generate the threshold voltage without requiring any large area resistors and with the system clock active only during the reception of data, thus minimizing energy consumption. Latency is also minimized as the threshold is generated within the first received bit of the packet. The reception of packets with no limits on their length is made possible by continuously updating the threshold, which also allows correct operation even in case of amplitude variations in the incoming signal during the data reception. It has been implemented and verified through post-layout simulations in an STMicroelectronics 90-nm CMOS technology with a 0.6-V supply, targeting a 1-kbps bitrate. It occupies an area lower than 0.001 mm
²
, which is less than 1% of the area of a standard RC-based TVG implemented in the same technology. A prototype of the proposed TVG is currently under fabrication.