Switched-capacitor fast start-up scheme for bandgap circuits

An apparatus, comprising:

• a bandgap voltage generating circuit having a plurality of current paths, each current path comprising a field effect transistor (FET), and gates of the FETs of the plurality of current paths coupled together, wherein the bandgap voltage generating circuit comprises a first switching device coupled between an upper voltage rail and the gates of the FETs, wherein the first switching device is configured to close in response to an enable signal being deasserted, and open in response to the enable signal being asserted;
• a pull-down start-up circuit coupled to the gates of the FETs of the plurality of current paths of the bandgap voltage generating circuit, the pull-down start-up circuit comprising a pull-down transistor configured to pull down voltages at the gates of the FETs upon start-up of the bandgap voltage generating circuit;
• and
• a secondary start-up circuit comprising a switched-capacitor circuit coupled to the gates of the plurality of FETs of the plurality of current paths of the bandgap voltage generating circuit, the switched-capacitor circuit configured to draw additional current from the gates of the FETs upon the start-up of the bandgap voltage generating circuit.

A method, comprising:

• partially charging a capacitor in response to disabling a bandgap voltage generating circuit;
• and
• enabling the bandgap voltage generating circuit comprising:
• pulling down voltages at gates of a set of field effect transistors (FETs);
• and
• further charging the capacitor to draw additional current from the gates of the set of FETs.