The Si4133W is a monolithic integrated circuit that performs RF and IF synthesis for GSM/GPRS and W-CDMA wireless communications. In dualmode GSM/UMTS handsets, the Si4133W meets demanding requirements for very low phase noise and fast settling time for both modes. The Si4133W integrates three complete phase-locked loops (PLLs) on a single die including VCOs, loop filters, reference and VCO dividers, and phase detectors. Dividers and powerdown settings are programmable through a three-wire serial interface.