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. 08, 1995
Filed:
Oct. 20, 1992
James T Sundby, Tracy, CA (US);
Exar Corporation, San Jose, CA (US);
Abstract
An accurate and stable low voltage detect circuit that provides a low voltage detect signal with minimal variation over process and temperature without trimming requirements. The power supply voltage is divided by a resistor voltage divider and compared to the output voltage of a bandgap reference circuit at the inputs of a comparator. The output of the comparator indicates power-on when the voltage divided power supply raises above the bandgap reference voltage. The low voltage detect circuit of the present invention will generate a correct low voltage detect signal even at power supply voltages too low for much of the rest of the circuit to operate properly. At low enough Vcc voltages, a transistor switch disconnects the resistor voltage divider from Vcc, causing all voltages taps off of the resistor voltage divider to drop to ground. Additionally, especially designed bandgap reference and comparator circuits ensure proper operation of the low voltage detect circuit at low power supply voltages.