US 11,705,861 B1
Fast startup crystal oscillator circuit with programmable injection time and adaptive startup time to achieve high amplitude oscillation
Mohamed M. Elkholy, Cedar Park, TX (US); Francesco Barale, North Kingstown, RI (US); Tiago Pinto Guia Marques, Austin, TX (US); Steffen Skaug, Oslo (NO); and Håkon Børli, Bekkestua (NO)
Assigned to Silicon Laboratories Inc., Austin, TX (US)
Filed by Silicon Laboratories Inc., Austin, TX (US)
Filed on Jun. 29, 2022, as Appl. No. 17/853,070.
Int. Cl. H03B 5/06 (2006.01); H03B 5/36 (2006.01); H03L 7/099 (2006.01)
CPC H03B 5/06 (2013.01) [H03B 5/36 (2013.01); H03B 5/364 (2013.01); H03L 7/099 (2013.01); H03B 2200/0012 (2013.01)] 22 Claims
OG exemplary drawing
 
1. A method for starting up a crystal oscillator comprising:
injecting a first clock signal into a first node of a crystal of the crystal oscillator during a startup phase of the starting up using a first tristate driver;
injecting a second clock signal into a second node of the crystal during the startup phase using a second tristate driver, the first clock signal and the second clock signal being anti-phase signals;
disabling the injecting of the first and second clock signals responsive to an end of a predetermined time period;
enabling a first amplifier circuit coupled across the first node and the second node during the startup phase and during an intermediate phase of the starting up following the startup phase; and
ending the intermediate phase responsive to an amplitude of a first node voltage on the first node exceeding a first voltage threshold.