PLL Loop Filter and its influence on speed
The lock speed, if far off frequency, is simply the time to charge that loop filter capacitor to be near the final frequency, whereupon the standard 2nd order loop dynamics will occur.

If far off frequency, the PFD will provide a beatnote of charge injection; thus a 1MHz frequency diffenence will display a 1MHz beatnote with 50% duty cycle.

If the Iloop is 100uA, then 50% of that is available to slew the Capacitor voltage.

A 1uF cap, give 50uA current, will slew at dV/dT = I/C = 50 volts/second.