4.2 A 1.8-to-3.0GHz Fully Integrated All-In-One CMOS Frequency Management Module Achieving -47/+42ppm Inaccuracy from -40 to $\mathbf{95}^{\circ}\mathbf{C}$ and -150/+70ppm After Accelerated Aging

Accurate and stable frequency-management modules (FMMs) are a critical component in wired/wireless communication systems since they determine key metrics such as data rate and bit-error rate. Conventional FMMs utilize a crystal reference to stabilize a frequency synthesizer with configurable output frequencies, as shown in Fig. 4.2.1 (top). However, using a bulky off-chip crystal can, in some cases, add too much cost and/or size for small IoT applications. Replacing the crystal with other off-chip references based on MEMS/BAW/SAW-type structures [1] doesn't quite solve this problem; the best solution would be full on-chip integration. However, on-chip frequency references, commonly implemented with RC cores (Fig. 4.2.1 bottom left), have difficulty in meeting the frequency accuracy requirement of typical wired/wireless protocols [2]. Moreover, RC-based references exhibit an unacceptable frequency spread due to their poor aging performance, for example with worse than a±1030ppm spread after accelerated aging even with methods such as redundancy design and employment of different CMOS resistors [3], [4]. Importantly, prior work has struggled simply to build an on-chip reference suitable for crystal-replacement, and has not taken the further step of integrating the on-chip reference into a synthesizer to build a fully-integrated FMM - a step necessary to prove the viability of full on-chip integration for low-cost IoT applications.