Charge pump

Abstract

The invention concerns a controllable current source, comprising supply terminals (12, 14) for the application of two supply potentials (V1, V2), an output terminal (16) for current delivery, which is connected via a first current path (18) with the first supply terminal (12) and via a second current path (20) with the second supply terminal (14), with the current paths (18, 20) each having a current control device (22, 24), which can be activated by a current control signal (S1, S2), as well as an output side current adjustment device (26, 28). According to the invention, it is provided that the current paths (18, 20) are each allocated a potential adjustment device, by means of which, when the current control device (22, 24) is inactive, a predetermined adjustment potential, whose value lies between the two supply potentials, is applied to an intermediate section (30, 32), which lies between the current control device and the current adjustment device. In this way, the performance characteristics of the current source are improved, in particular, negative injection and disturbances in the output current can be avoided. When the current source is used in a PLL, the jitter behavior at the output of the VCO is significantly improved.

Dependencies are inferred from the claim text.