A 3 /spl mu/W, 2 MHz CMOS frequency reference for capacitive sensor applications

In this paper, measurement results for a micropower 2 MHz CMOS frequency reference circuit fabricated with a 0.13 mum CMOS process are presented. This frequency reference circuit, based on source-coupled CMOS multivibrator, provides the clock signal for a read-out circuit of a capacitive sensor. In addition to low power consumption, good frequency stability is required. Supply independent biasing and symmetrical loads are used to optimize the frequency stability. The typical power consumption is 3.0 muW at room temperature with 1.8 V supply voltage. When properly calibrated, the frequency stays within plusmn2.5% of the nominal oscillation frequency in the operating voltage range of 1.8-2.5 V (with plusmn10% variation) over a temperature range from -35 to +85 degC. The measured phase noise and jitter agree well with the simulations