Wireless sensor nodes in battery-powered internet-of-things (loT) applications require a stable on-chip frequency reference with low energy (<10 pJ / cycle) and high frequency stability (below ±300ppm). CMOS RC frequency references are promising due to their low-cost integration and high energy efficiency  –. Conventional RC references, however, achieve only moderate accuracy (a few %) due to the large temperature coefficient (TC) of on-chip resistors . First-order TC compensation can be achieved by combining resistors with complementary TCs , . Although this is energy efficient (<6 pJ / cycle), it only partially compensates for the resistors’ high-order TCs, limiting the resulting accuracy to about ±500 ppm. Better accuracy (±100 ppm ) can be achieved by using the output of a digital temperature sensor (TS) to perform a polynomial correction of the phase-shift (μp,T) of an RC filter (Fig. 31.2.1). Alternatively, the phase-shifts (μp. and μN) of two RC filters with complementary TCs can be linearized (Tp. and T N ) and combined in the digital domain. Such dual-RC frequency references can also achieve good accuracy (±200 ppm ). However, both architectures employ an analog phase-domain ΔΣ modulator (Φ−ΔΣM) for each RC filter, which consumes significant energy (25pJ/cycle  and 107pJ/ cycle ) and area (0.3mm2. and 1.65mm2).
|Title of host publication||2021 IEEE International Solid-State Circuits Conference, ISSCC 2021 - Digest of Technical Papers|
|Publisher||Institute of Electrical and Electronics Engineers (IEEE)|
|Number of pages||3|
|Publication status||Published - 2021|
|Event||2021 IEEE International Solid-State Circuits Conference, ISSCC 2021 - San Francisco, United States|
Duration: 13 Feb 2021 → 22 Feb 2021
|Name||Digest of Technical Papers - IEEE International Solid-State Circuits Conference|
|Conference||2021 IEEE International Solid-State Circuits Conference, ISSCC 2021|
|Period||13/02/21 → 22/02/21|
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