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:
Jul. 04, 2000
Filed:
Dec. 21, 1998
Tom Youssef, Dallas, TX (US);
STMicroelectronics, Inc., Carrollton, TX (US);
Abstract
A power supply switching circuit ensures stable, timely, and accurate transition between a primary power source and a secondary power source of an integrated circuit. A comparison element of the circuit compares a first voltage signal derived from a primary voltage of the primary power source to a second voltage signal, also derived from the primary voltage but having a different rate of change than the first voltage signal, to generate a compare output signal. The first and second voltage signals are characterized as being equal to each other when the primary voltage is equal to a predetermined crossover point at which the integrated circuit device will be powered by the primary voltage. When the primary voltage is less than the predetermined crossover point, a transistor element of a reference leg of a current mirror of the power supply switching circuit operates in back-bias mode and is sized large enough to ensure that the reference leg generates a large enough current to stabilize operation of the comparison element as the primary voltage ramps up until the primary voltage exceeds the predetermined crossover point.