Patent ID: 7276948
Filing Date: 2007-10-02
Classification: H03K

Abstract:
1. A resistor start-up circuit for a reset circuit, comprising: a current source having a control input, and a current output for delivering a first current, said current source being coupled to a power supply voltage; a first current mirror having a mirror input and a mirror output, said mirror input being coupled to said current output for receiving the first current, and in response thereto for delivering a second current at said mirror output; a first transistor switch, having a control electrode, a first output electrode and a second output electrode, said first output electrode being coupled to said mirror output of said first current mirror; a second current mirror having a mirror input and a mirror output, wherein said mirror input is coupled to said second output electrode of said first transistor switch; said control input of said current source is coupled to a voltage reference signal wherein said current source delivers the first current when the power supply voltage increases to a first predetermined value, and said input electrode of said first transistor switch is coupled to the voltage reference signal, wherein said first transistor conducts the second current to said mirror input of said second current mirror when the power supply voltage increases to a second predetermined value; wherein said mirror output of said second current mirror delivers a current to a resistor divider in response to the second current being generated, and further comprising: a first transistor having a control electrode, a first output electrode and a second output electrode, said first output electrode being coupled to said current output of said current source, and said second output electrode being coupled to said mirror input of said first current mirror; and a second transistor having an control electrode, a first output electrode and a second output electrode, said control electrode being coupled to the current reference signal, said first output electrode being coupled to the power supply voltage, and said second output electrode being coupled to said mirror input of said second current mirror, wherein the first current delivered by said current source to said first transistor is mirrored as a fourth current by said second transistor when the power supply voltage is equal to or greater than the first predetermined value.