Charge pump for phase locked loop including main and auxiliary pump

Abstract

A charge pump includes a main pump circuit having a main first and second switching transistors and an auxiliary pump circuit. The charge pump is configured to provide a variable bias to at least the first switching transistor in response to operation of the auxiliary pump circuit. The auxiliary pump circuit can include auxiliary first and second switching transistors corresponding to the first and second switching transistors of the main pump circuit. The auxiliary first and second switching transistors control a charging level for auxiliary charge storage. A bias transistor of a controllable current source for the first switching transistor of the auxiliary pump circuit is responsive to a charging level of the auxiliary charge storage to provide a self-regulating bias to the first switching transistor of the auxiliary pump circuit. A bias transistor of a controllable current source for the first switching transistor of the main pump circuit is also responsive to a charging level of the charge storage for regulating the operation of the main pump circuit. A further main pump circuit can also be provided with the further main pump circuit also being regulated by the operation of the auxiliary pump circuit. The first switching transistors are typically PMOS transistors, with the second switching transistors typically being NMOS transistors.