Patent ID: 6222399
Filing Date: 2001-04-24
Classification: G05F

Abstract:
A bandgap start-up circuit, comprising:a bandgap circuit having a bandgap voltage node and a critical node;an inverter having a hysteretic feedback loop, an output node, and an input connected to the bandgap voltage node of the bandgap circuit; andan NMOS switching transistor having a gate connected to the output node of the inverter, a drain connected to the critical node of the bandgap circuit, and a source connected to ground;whereby, when the voltage at the input of the inverter falls below a first transistion voltage, the output of the inverter switches high, switching on the NMOS switching transistor and drawing current through the critical node of the bandgap circuit causing the bandgap circuit to start normal operation, and when the voltage of the input of the inverter goes higher than a second transition voltage, the inverter output switches low, switching off the NMOS switching transistor such that no current is drawn from the critical node of the bandgap circuit.