The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 10, 2013
Filed:
Apr. 04, 2011
Barry Britton, Slatington, PA (US);
Richard Booth, Riegelsville, PA (US);
Phillip L. Johnson, Hellertown, PA (US);
Yang Xu, Shanghai, CN;
Tawei David LI, San Jose, CA (US);
Barry Britton, Slatington, PA (US);
Richard Booth, Riegelsville, PA (US);
Phillip L. Johnson, Hellertown, PA (US);
Yang Xu, Shanghai, CN;
Tawei David Li, San Jose, CA (US);
Lattice Semiconductor Corporation, Hillsboro, OR (US);
Abstract
A phase locked loop (PLL) circuit is provided with selectable feedback paths. In one example, a method of operating a device includes passing a clock signal provided by a PLL circuit of the device through an internal feedback path of the PLL circuit to provide a first input signal to the PLL circuit while at least one external circuit of an external feedback path of the device is disabled during a low power operation mode of the device. The method also includes detecting a lock between the first input signal and a reference signal during the low power operation mode. The lock indicates that the clock signal is operating at a frequency used during a normal operation mode of the device. The method also includes passing the clock signal through the external feedback path to provide a second input signal to the PLL circuit. The method also includes switching from detecting a lock between the first input signal and the reference signal to detecting a lock between the second input signal and the reference signal if the external circuit is enabled for the normal operation mode.