analog_guru
Member level 1
You need to look at the whole picture to determine what the charge pump current should be.
The place to start is the PLL bandwidth. You need to consult any PLL book to find what the bandwidth of the PLL is (I mean the equation). What you will find is that the BW is a function of the Kc (charge pump gain) Kvco (The VCO gain), Loop Filter transfer function (which will have the capacitors values in it) and Kp(the phase detector gain). Then start assigning practical values for those parameters. After that you start calibrate those values to meet your jitter and BW specs.
Typical values for PLL BW is 1MH-50MHz. Typical Charge pump currents is 20uA-200uA (As a starting point, I will use 100uA).
Hope that helps...
The place to start is the PLL bandwidth. You need to consult any PLL book to find what the bandwidth of the PLL is (I mean the equation). What you will find is that the BW is a function of the Kc (charge pump gain) Kvco (The VCO gain), Loop Filter transfer function (which will have the capacitors values in it) and Kp(the phase detector gain). Then start assigning practical values for those parameters. After that you start calibrate those values to meet your jitter and BW specs.
Typical values for PLL BW is 1MH-50MHz. Typical Charge pump currents is 20uA-200uA (As a starting point, I will use 100uA).
Hope that helps...
