Measuring KP on PLL chip

this procedure measures the maximum charge pump current. The actual KP does not match exactly with the formula given for the current setting resistor.

CP outputs current pulses in which the duty cycle is proportional to frequency difference at the R and N divider output. When measuring current with the ammeter, the result is a average. This average current then varies according to the magnitude of the frequency error.
To measure the maximum current, ground either the RF or Ref input.

Disconnect CP output to ammeter. Connect other end of ammeter to Vp or ground depending on PFD polarity.