ArXiv · 2026
The offset and gain of voltage-to-time converters (VTCs) in time-domain circuits vary with process, supply, and temperature. This work presents a VTC whose nonvolatile input-referred offset trim is the programmed multilevel state of the ferroelectric field-effect transistor (FeFET) that converts the input. Fabricated in 28-nm CMOS, the 6.07-μm² VTC consists of a current-starved inverter with the FeFET and a parallel NMOS leaker in its tail, a capacitor bank, and a following inverter. The programmed state shifts the transfer curve onto the input range, leaving the gain to the capacitor bank and the leaker bias. Measured at 10 MS/s, centered states weaken the second harmonic from -12.5 dB in the low-threshold state to -32.2 dB and lower the static integral nonlinearity (INL) at 5 bit from 2.42 to 0.92 LSB. Post-layout simulations indicate that the proposed VTC can operate at 500 MS/s, drawing 2.0~μW from a 0.9-V supply, with nearly unchanged distortion and gain up to 700 MS/s. Across simulated process corners and ±10 % supply variation, the input-referred offset is calibrated to within 10 mV and the gain to within 4 % of nominal by adjusting the programmed state and leaker bias.
Try inveni