Patent ID: 6400212
Filing Date: 2002-06-04
Classification: G01R,G05F

Abstract:
A monitoring circuit for determining when a reference voltage generated by a bandgap reference voltage circuit is stable, wherein the bandgap reference voltage circuit includes a current source configured to provide a first current and second current that is substantially proportioned to the first current, a first circuit branch that includes a first resistor wherein the first circuit branch is configured to receive the first current, a first solid state device coupled to the first circuit branch, wherein the first resistor is coupled between the current source and the first solid state device, a second circuit branch that is configured to receive the second current, and a second solid state device coupled to the second circuit branch, the reference voltage being provided to an external circuit that is different than the bandgap reference voltage circuit, the monitoring circuit comprising:a first input node connected to the second circuit branch of the bandgap reference voltage circuit between the second solid state device and the current source to receive a first test voltage; a second input node connected to the first circuit branch of the bandgap reference voltage circuit to receive a second test voltage therefrom; and a comparator circuit connected to the first input node to receive the first test voltage therefrom and to the second input node to receive the second test voltage therefrom, and that generates a digital enable output signal when the first test voltage is less than the second test voltage, the digital enable output signal being provided to the external circuit to enable operation of the external circuit, whereby the external circuit is enabled for operation utilizing the reference voltage only when the reference voltage is stable.