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:
Apr. 12, 1994
Filed:
Nov. 25, 1992
Jules J Jelinek, San Francisco, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A power on reset circuit that incorporates a voltage divider, and current reference generator and a switching circuit. The voltage divider generates an output voltage which is a predefined fraction of the supply voltage. The current reference generator generates a reference current which controls a first current mirror in the switching circuit. The switching circuit, which has a sharply sloped voltage transfer characteristic, includes a first transistor that is gated by the voltage divider output and coupled to the first current mirror at a first circuit node. The first transistor draws current from the first current mirror only when the voltage divider output exceeds a threshold voltage, causing the switching circuit to develop a first reset voltage on the first circuit node. The power on reset circuit may also include an inverter having an input coupled to the first circuit node and producing a second reset voltage on a second circuit node. The inverter comprises a current mirror coupled to the current reference generator and a transistor gated by the first reset voltage and coupled the to current mirror at the second circuit node to draw current from the current mirror only when the first reset voltage exceeds the threshold voltage. Additionally, the power on reset circuit may include various types of filters coupled to the voltage divider output and/or the first circuit node to suppress noise in the voltage supply.