发明申请
- 专利标题: Programmable frequency detector for use with a phase-locked loop
- 专利标题(中): 可编程频率检测器,用于锁相环
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申请号: US10714037申请日: 2003-11-14
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公开(公告)号: US20050105660A1公开(公告)日: 2005-05-19
- 发明人: Thomas Knotts
- 申请人: Thomas Knotts
- 主分类号: H03D13/00
- IPC分类号: H03D13/00 ; H03L7/087 ; H03L7/089 ; H03L7/113 ; H03D3/24
摘要:
A frequency detector for use with a PLL utilizes a counter and a preset value to produce frequency information related to a VCO signal. The frequency information is used to control the frequency of the VCO signal and to determine whether the VCO signal should be controlled by the frequency detector or a phase detector. Using the counter and preset value involves establishing a preset value that is used to obtain the desired frequency information. The preset value is set such that the counter is at one-half full-scale at the end of a known time period when the VCO signal is oscillating at a target frequency. When the preset value is set to such a value, the most significant bit of the counter after the known time period indicates whether the frequency of the VCO signal is above or below the target frequency.