Patent ID: 7295050
Filing Date: 2007-11-13
Classification: H03K

Abstract:
1. A power-up reset circuit, comprising: a detecting portion receiving a power voltage and outputting a node voltage, the node voltage being less than the power voltage; an output portion outputting a detecting signal in response to the node voltage; a first resistance adjuster including a first resistor and a first transistor, the first transistor being arranged in parallel with the first resistor and receiving a feedback voltage, the first transistor increasing a resistance of the first resistance adjuster based on the received feedback voltage during a normal operation, the increased resistance creating a divergence between a first threshold voltage and a second threshold voltage and reducing the node voltage during normal operation, wherein the first resistance adjuster is coupled between the detecting portion and a ground voltage, and the power-up reset circuit outputs the feedback voltage of the power voltage level when the power voltage goes beyond the first threshold voltage during a power-up operation and outputs the feedback voltage of a low level when the power voltage goes below the second threshold voltage during the normal operation; and a second resistance adjuster included within the output portion, the second resistance adjuster including a second resistor and a second transistor, the second transistor being arranged in parallel with the second resistor and receiving the feedback voltage, the second transistor increasing a resistance of the second resistance adjuster based on the received feedback voltage during normal operation, the increased resistance creating a divergence between a first threshold voltage and a second threshold voltage, and wherein the output portion outputs the detecting signal depending on the resistance of the first resistance adjuster.