发明授权
US5838204A Phase locked loop with multiple, programmable, operating frequencies, and an efficient phase locked loop layout method 失效
具有多个可编程工作频率的锁相环以及高效的锁相环布局方法

Phase locked loop with multiple, programmable, operating frequencies,
and an efficient phase locked loop layout method
摘要:
An application specific integrated circuit (ASIC) including a phase-locked loop (PLL) circuit operably coupled to an internal clock and an external clock. The present PLL circuit includes an internal phase detector circuit, an internal charge pump operably coupled to the phase detector circuit, a loop filter operably coupled to the charge pump, and an internal programmable voltage-controlled oscillator 200, 300. The internal programmable voltage controlled oscillator includes a plurality of delay elements, which have a respective switch to turn-on the delay elements. A storage device having a plurality of outputs providing selected switch signals to the voltage oscillator program one of a plurality of center frequencies. Each of the outputs is operably coupled respectively to the delay elements through the respective switch. The switch isolates a first group of delay elements from a second group of delay elements. Setting simultaneous operating (SSO) limits for an application specific integrated circuit (ASIC) having a phase-locked loop sets a limit for the PLL pins.
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