A Threshold Voltage Generator (TVG) circuit for Continuous-Time Comparators is presented. It generates the threshold without requiring the use of any resistor at all. It exploits the system clock only during the reception of data, thus minimizing energy consumption. The proposed TVG circuit was implemented in a 90-nm CMOS technology with a 0.6-V supply voltage, targeting a 1-kbps bitrate and occupies an area lower than 0.001 mm2. Post-layout simulation results demonstrates that the proposed TVG does not require the need for any preamble and enables the reception of hundreds-bit packets and correct operation even in case of amplitude variations during the data reception.