Patent ID: 6819163
Filing Date: 2004-11-16
Classification: G05F

Abstract:
A switched capacitor voltage reference circuit that operates on a cycle that includes a reset phase and a generation phase to generate an output voltage on an output terminal that is relatively predictable with temperature variations, the switched capacitor voltage reference circuit comprising the following:an amplifier having inverting and non-inverting input terminals and at least one output terminal, the output terminal configured to be at least capacitively coupled to the inverting input terminal during the reset phase to define a first feedback loop; a first capacitor having a first and second terminal, the first terminal of the first capacitor at least capacitively coupled to the inverting input terminal of the amplifier, the non-inverting terminal of the amplifier coupled to a first substantially fixed voltage source; a second capacitor having a first and second terminal, the first terminal of the second capacitor at least capacitively coupled to the inverting input terminal of the amplifier; a PN junction having a first terminal that is at least capacitively coupled to a second terminal of the first capacitor, a second terminal of the PN junction being coupled to a second substantially fixed voltage source, the second terminal of the second capacitor being configured to be at least capacitively coupled to the first terminal of the PN junction during the reset phase and to the second terminal of the PN junction during the generation phase; a first current source that is configured to supply a first current magnitude through the PN junction during the first time period; a second current source that is configured to supply a second current magnitude through the PN junction during the second time period, the second current magnitude being different than the first current magnitude; a transconductance circuit that has at least one input terminal and at least one output terminal, the input terminal of the transconductance circuit being at least capacitively coupled to the output terminal of the amplifier, the output terminal of the transconductance circuit being at least capacitively coupled to an output terminal of the switched capacitor voltage regulator circuit, the transconductance circuit being configured to generate a current change that is approximately proportional to a change in voltage at the input terminal of the transconductance circuit; and a third capacitor having a first and second terminal, the first terminal of the third capacitor at least capacitively coupled to the inverting input terminal of the amplifier, the second terminal of the capacitor at least capacitively coupled to the output terminal of the switched capacitor voltage reference circuit during the generation phase, and to a third substantially fixed voltage source during the reset phase.