Wideband High Stability MEMS-Based AC Voltage References

This paper presents the high level of stability of voltage references operated in alternating current (ac) and based on the pull-in effect in split-finger microelectromechanical systems (MEMS). It shows results of both electrical and mechanical characterizations, as well as the development of optimized readout electronics. The new aspects in this paper are related to the new architecture of the MEMS allowing minimizing the effect of leakage capacitances on the stability of the voltage reference and avoiding compensating any “built-in voltage” generated at metal-semiconductor interfaces. Hence, the voltage stability of MEMS devices, designed to serve as ac voltage standards ranging from 2 to 14 V, has been measured over more than 150 h with a relative deviation from the mean value not exceeding 1 ×10^-6 (1σ standard deviation) at 100 kHz. The temperature dependence of these devices has been found ten times smaller than those previously reported. In addition, MEMS-based references are theoretically independent of frequency beyond the mechanical resonant frequency. The frequency stability has been successfully tested between 40 and 300 kHz.