Silicon Laboratories' Criterium products are single-chip RF synthesizers that integrate three VCOs, loop filters, reference and VCO dividers and phase detectors in a low-profile CMOS IC. The Si4135 synthesizes frequencies for the U.S. PCS and cellular bands, performing RF synthesis at 1.719 to 1.780 GHz and 954 to 980 MHz, and IF synthesis at 420.76 and 170.76 MHz. The Si4135 also synthesizes RF frequencies from 1.620 GHz to 1.650 GHz for the Korean PCS band, and an IF frequency of 440.76 MHz. The cellular band frequencies in Korea are the same as the U.S., making the Si4135 suitable for PCS or cellular band Korean applications. The design of the Si4135 results in superior phase noise performance and provides settling times that easily meet CDMA and AMPS requirements using a stable integer-N architecture.