US 11,699,974 B1
Utilizing the LC oscillator of a frequency synthesizer as an injection source for crystal oscillator startup
Mohamed M. Elkholy, Cedar Park, TX (US); Mustafa Koroglu, Austin, TX (US); and Wenhuan Yu, Austin, TX (US)
Assigned to Silicon Laboratories Inc., Austin, TX (US)
Filed by Silicon Laboratories Inc., Austin, TX (US)
Filed on Jun. 29, 2022, as Appl. No. 17/853,064.
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); H03L 7/099 (2013.01)] 21 Claims
OG exemplary drawing
 
1. A method for starting up a crystal oscillator circuit comprising:
configuring portions of a phase-locked loop (PLL) using stored parameters, the configuring being responsive to a wakeup event;
generating an injection clock signal using the PLL configured with the stored parameters, the injection clock signal having a frequency that is substantially equal to a crystal oscillator frequency of the crystal oscillator circuit;
supplying the injection clock signal to the crystal oscillator circuit;
generating anti-phase signals using the injection clock signal; and
injecting the anti-phase signals into a crystal during startup of the crystal oscillator circuit.