Patent ID: 7567133
Filing Date: 2009-07-28
Classification: H03L

Abstract:
1. Phase-locked loop circuitry comprising: charge pump circuitry configured to generate a pump current based on a phase of an input signal; loop filter circuitry configured to receive the charge pump current, the loop filter circuitry comprises a first capacitor connected between a control voltage and ground, a first resistor connected between the control voltage and an integration node, an operational amplifier having a positive terminal connected to the integration node, a second capacitor connected between the integration node and ground, a second resistor between the control voltage and a negative terminal of the operation amplifier, and a feedback link connecting an output of the operational amplifier to the negative terminal of the operational amplifier; and the first resistor, the second resistor, and the operational amplifier form drag current circuitry configured to generate a drag current to draw charge in the opposite direction from the charging current from the first capacitor.