Patent ID: 7256621
Filing Date: 2007-08-14
Classification: H03K

Abstract:
1. A keeper circuit for use in a circuit powered by a voltage provided between a first supply line and a second supply line, the keeper circuit for selectively maintaining an intermediate node of the circuit at a first voltage level in opposition to a leakage current being conducted between the intermediate node and the second supply line, the keeper circuit comprising: a keeper transistor having a first conduction terminal, a second conduction terminal, and a modulation terminal, the modulation terminal receiving a signal indicating whether the keeper transistor is to maintain an intermediate node at a first voltage level; a first transistor of a first conductivity type having a first conduction terminal, a second conduction terminal, and a modulation terminal, one of the conduction terminals of the first transistor being coupled to a conduction terminal of the keeper transistor to provide a series circuit of the transistors, the series circuit being coupled between the intermediate node and the first supply line; a second transistor of the first conductivity type having a first conduction terminal, a second conduction terminal, and a modulation terminal, the second transistor being coupled to the first transistor in a current-mirror relationship such that the maximum amount of current conducted by the first transistor through its conduction terminals is related to the current conducted by the second transistor through its conduction terminals; and a sensing network having a first conduction terminal coupled to the first conduction terminal of the second transistor and a second conduction terminal coupled to a source of potential, the sensing network comprising at least one transistor of a second conductivity type opposite to the first conductivity type and generating a current at its first conduction terminal that is in relation to the leakage current being conducted between the intermediate node and the second supply line.