LANSDALE Semiconductor, Inc.

ML12202

www.lansdale.com

Page 6 of 11

Issue A

PHASE CHARACTERISTICS/VCO CHARACTERISTICS

The phase comparator in the ML12202 is a high speed digital phase frequency detector circuit. The circuit determines the

“lead”or “lag” phase relationship and time difference between the leading edges of the VCO (fp) signal and the reference (fr)

input. Since these edges occur only once per cycle, the detector has a range of ±2

π radians. The phase comparator outputs are

standard CMOS rail–to–rail levels (VP to GND for

φP and VCC to GND for φR), designed for up to 20MHz operation into a

15pF load. These phase comparator outputs can be used along with an external charge pump to enhance the PLL characteristics.

The operation of the phase comparator is shown in Figures 3 and 5. The phase characteristics of the phase comparator are con-

trolled by the FC pin. The polarity of the phase comparator outputs,

φR and φP, as well as the charge pump output Do can be

reversed by switching the FC pin.