Self-oscillating regulated low-ripple charge pump and method

Abstract

Charge pump circuitry (30) compares bottom plate voltages of first (Cl) and second (C2) flying capacitors in a current mode charge pump (IB) to a reference value (VDD-V28) by means of a comparator (20) which drives a flip-flop (22) that generates first (Fl) and second (F2) complementary phase signals. The first and second phase signals control switching of the flying capacitors to determine a flying capacitor swapping frequency just low enough to prevent saturation of a discharge current source (10) that discharges the flying capacitors into an output conductor (3).

Description

technical field [0001] The present invention relates generally to integrated charge pump circuits, and more particularly to improvements in which power consumption is reduced and the amount of integrated circuit chip area required is reduced. Background technique [0002] The use of an on-chip charge pump in an integrated circuit op amp to bootstrap a current source at the end of its input stage provides an increased rail-to-rail common-mode input voltage range of the op amp. The boosted output voltage produced by the charge pump needs to have low ripple voltage since the ripple voltage creates noise in the terminal current that then propagates to the output of the operational amplifier. It is desirable for the on-chip charge pump to consume as little current and power as possible. [0003] figure 1 A low ripple on-chip current mode charge pump that has been used in the assignee's OPA365 operational amplifier is shown, which is considered to be the closest prior art. exis...

AI Technical Summary

Problems solved by technology

Whenever the flying capacitor function is effectively swapped, some energy is lost or wasted due to the need to recharge one of the parasitic capacitances Cp1 or Cp2

What is actually lost is the current required to recharge the parasitic capacitance Cp1 or Cp2

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