Abstract: A circuit to generate a reference voltage from a power supply based on a predetermined voltage level includes a follower connected between the power supply and a current source to output the reference voltage. An amplifier, connected in a negative feedback arrangement with the reference voltage and the predetermined voltage level, provides an output used to control the follower. A switched capacitor filter is provided in a feedback leg of the negative feedback arrangement. Switching of capacitors in the switched capacitor filter occurs to synchronism with phase signals for driving a switched capacitor analog to digital converter, such that the reference voltage is sampled during quiescent periods of the switched capacitor analog to digital converter.

Abstract: The present invention provides a circuit and method for generating a regulated voltage from a first voltage of a first voltage source. The circuit includes a driver for generating a drive signal. A charge pump is coupled to the driver for generating a pump voltage from the first voltage source. The charge pump generates the pump voltage in response to the drive signal. The charge pump includes at least two charging modes. An amplifier has a reference input coupled to a reference voltage, and a sense input coupled to a sense signal representative of the pump voltage. In response to a difference between the reference voltage and the sense signal, the amplifier generates an output to control the driver. A pump controller is coupled from the amplifier output to the charge pump. The pump controller includes a measuring device that is operable in response to a mode criteria, to select a charging mode of the charge pump.