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:
Aug. 23, 1994
Filed:
Feb. 11, 1993
Wallace E Matthews, Richardson, TX (US);
Benchmarq Microelectronics, Inc., Carrollton, TX (US);
Abstract
A power control circuit (10) is operable to select between a backup battery (14) on a terminal (16) and a primary power supply voltage on a terminal (12) to output a voltage to a powered device (20). The two voltages are compared by a comparator (28) that drives a well bias node (44) with transistors (36) and (38). The comparator (28) selects the highest of two voltages on either the battery supply terminal (16) or the power supply terminal (12) to power the node (44), which node (44) is then connected to the wells of switching transistors (40) and (42) which are operable to select the battery terminals (16) in the event of a fail of the power supply on terminal (12). This decision is made with a power failure device (20). In the event that both the primary power supply voltage falls below a predetermined threshold and the battery supply voltage is at a higher level, the battery (14 ) is selected for output on the line (18).