| 摘要 |
The 3 dB frequency bandwidth of a phase-locked loop (PLL) is determined by measuring the frequency of a voltage controlled oscillator (VCO) signal when an up charging current is applied, measuring the frequency of the VCO signal when a down charging current is applied, and then using the two frequency measurements to calculate the 3 dB frequency bandwidth of the PLL. The up and down charging currents can be applied through a charge current switch system and the frequency measurements can be made with a frequency counter, both of which are monolithically integrated with the PLL. The technique for measuring the 3 dB frequency bandwidth can be applied to a first order or a second PLL. When applied to a second order PLL, the technique includes an initial frequency centering operation.
|
