Capacitor leakage compensation for PLL loop filter capacitor

Patent metadata

Field	Value
Publication number	US-9166607-B2
Application number	US-201213409348-A
Country	US
Kind code	B2
Filing date	Mar 1, 2012
Priority date	Mar 1, 2012
Publication date	Oct 20, 2015
Grant date	Oct 20, 2015

Abstract

An output portion of a charge pump receives control signals from a phase frequency detector and in response outputs positive current pulses and negative current pulses to a loop filter. A current control portion of the charge pump controls the output portion such that the magnitudes of the positive and negative current pulses are the same. Within the current control portion there is a “Charge Pump Output Voltage Replica Node” (CPOVRN). The voltage on this CPOVRN is maintained to be the same as a voltage on the charge pump output node. A capacitor leakage compensation circuit indirectly senses the voltage across a leaking capacitor of the loop filter by sensing the voltage on the CPOVRN. The compensation circuit imposes the sensed voltage across a replica capacitor, mirrors a current leaking through the replica, and supplies the mirrored current in the form of a compensation current to the leaking capacitor.

First claim

What is claimed is:

1. A circuit comprising:
a loop filter comprising a capacitor;
a charge pump comprising a charge pump output node, a first operational amplifier, and a Charge Pump Output Voltage Replica Node (CPOVRN), wherein the charge pump output node is coupled to the loop filter, and wherein the CPOVRN is directly coupled to a high impedance noninverting input lead of the first operational amplifier; and
a capacitor leakage compensation circuit having a second operatio…

Assignees

• Park Sunghyun
• Wang Shen
• Kim Young Gon
• Qualcomm Inc

Inventors

• Park Sunghyun
• Wang Shen
• Kim Young Gon

Classifications

• H03L7/093

  Electricity · mapped topic

• H03L7/0891 Primary

  Electricity · mapped topic