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:
Oct. 25, 1994
Filed:
Oct. 28, 1993
Michael W Hodel, Mesa, AZ (US);
William H Gulliver, Gilbert, AZ (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
A power-on reset circuit controls a PLL to prevent overshoot of the VCO during power-up. The power-on reset circuit asserts a control signal upon detecting the power supply potential to the PLL below a predetermined threshold. The control signal enables a pull-down transistor to attenuate the control voltage to the VCO and reduce the output frequency of the VCO. The control signal further blocks the input reference signal to the phase detector. With the input reference signal blocked, the phase detector produces only down pulses to the charge pump during subsequent high to low logic transitions of the feedback signal from the VCO thereby further discharging the loop node and reducing the output frequency of the VCO. Following power-up, the control signal disables the pull-down transistor and allows the input reference signal to reach the phase detector whereby the PLL begins normal frequency acquisition and lock sequencing.