Abstract
This article presents a 16-MHz RC frequency reference implemented in a standard 180-nm CMOS process. It consists of a frequency-locked loop (FLL) in which the output frequency of a digitally controlled oscillator (DCO) is locked to the frequency-phase characteristic of a Wien bridge RC filter. Since it is made from on-chip resistors and capacitors, the filter's characteristic is temperature dependent. To compensate for this, the control signal of the DCO is derived by digitizing the filter's output phase and combining it with the digital output of a Wheatstone bridge temperature sensor. After a two-point trim, this digital temperature compensation scheme achieves an inaccuracy of ±90 ppm from -45 °C to 85 °C. The frequency reference draws 220 $\mu \text{A}$ from a 1.8-V supply, with a supply sensitivity of 0.12%/V and a 320-ppb Allan Deviation floor for a 10-s stride.
Original language | English |
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Pages (from-to) | 2429-2437 |
Number of pages | 9 |
Journal | IEEE Journal of Solid-State Circuits |
Volume | 57 |
Issue number | 8 |
DOIs | |
Publication status | Published - 2022 |
Bibliographical note
Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-careOtherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.
Keywords
- Bandwidth
- CMOS
- digital frequency-locked loop (FLL)
- digitally controlled oscillator (DCO)
- Frequency control
- Frequency locked loops
- integrated frequency reference
- RC.
- Resistors
- Sensitivity
- System-on-chip
- Temperature sensors