Controllable current source for a phase locked loop
The invention concerns a controllable current source or “charge pump” ( 12 ) in an integrated circuit, comprising two supply terminals (K 1, K 2 ) for the application of two supply potentials (V 1, V 2 ) as well as an output terminal (Kout) for the delivery of an output current, connected via a first controllable current path (T 1 ) with the first supply terminal (K 1 ), and via a second controllable current path (T 2 ) with the second supply terminal (K 2 ). In order to improve the current source ( 12 ) with regard to the quality of the output signal, it is provided according to the invention that the controllable current source ( 12 ) furthermore has a replica (T 1′, T 2′ ) of the current paths (T 1, T 2 ) in their non-controlled state, of which a replica output terminal (Kout′) is connected via a current mirror (T 5 to T 8 ) with the output terminal (Kout).
1. An integrated circuit, comprising a phase locked loop ( 1 ), in which a controllable current source ( 12 ) is provided for at least indirect control of a controllable oscillator ( 16 ) of the phase locked loop ( 1 ), wherein the controllable current source ( 12 ) comprises:
a first and a second supply terminal (K 1 , K 2 ) for the application of a first and a second supply potential (V 1 , V 2 ) respectively,
an output terminal (Kout) for the delivery of an output current, connected via a first controllable current path (T 1 ) with the first supply terminal (K 1 ), and via a second controllable current path (T 2 ) with the second supply terminal (K 2 ), and
a replica (T 1 ′, T 2 ′) of the current paths (T 1 , T 2 ) in their non-controlled state, of which a replica output terminal (Kout′) is connected via a current mirror (T 5 -T 8 ) with the output terminal (Kout),
and wherein a supply voltage of the current mirror (T 5 -T 8 ) is adjusted as a function of a voltage or a potential that is tapped in the region of the oscillator ( 16 ).
2. The integrated circuit according to claim 1 , wherein each of the controllable current paths (T 1 , T 2 ) is formed by a transistor.