Low Noise Charge Pump Method and Apparatus

摘要

A charge pump method and apparatus is described having various aspects. Noise injection from a charge pump to other circuits may be reduced by limiting both positive and negative clock transition rates, as well as by limiting drive currents within clock generator driver circuits, and also by increasing a control node AC impedance of certain transfer capacitor coupling switches. A single-phase clock may be used to control as many as all active switches within a charge pump, and capacitive coupling may simplify biasing and timing for clock signals controlling transfer capacitor coupling switches. Any combination of such aspects of the method or apparatus may be employed to quiet and/or simplify charge pump designs over a wide range of charge pump architectures.

主权项

1. Charge pump apparatus for generating an output voltage supply within a circuit, comprising:
a) a transfer capacitor; b) a plurality of transfer capacitor coupling switches, each switchable between a conducting state and a nonconducting state under control of at least one charge pump clock output; and c) a charge pump clock generating circuit including a ring oscillator comprising an odd number of inverting driver sections cascaded sequentially in a ring such that each driver section has an output coupled to a next driver section input, wherein a first driver section is next after a last driver section and one of the driver section outputs constitutes a particular charge pump clock output controlling at least one of the transfer capacitor coupling switches, and wherein each driver section includes:
i) circuitry configured as an active current limit to limit a rate of rise of voltage at the driver section output, andii) circuitry configured as an active current limit to limit a rate of fall of voltage at the driver section output;wherein the plurality of transfer capacitor coupling switches are coupled to the transfer capacitor, and are controlled so as to couple the transfer capacitor to a voltage source during periodic first times, and to couple the transfer capacitor to the output voltage supply during periodic second times that are not concurrent with the first times.