The LMX237X family of monolithic, integrated dual frequency synthesizers, including prescalers, is designed to be used as a first and second local oscillator for dual mode or dual conversion transceivers. It is fabricated using National's 0.5u ABiCV silicon BiCMOS process. The LMX237X contains two dual modulus prescalers. A 32/33 or a 16/17 prescaler can be selected for the 2.5 GHz and 2.0 GHz RF synthesizers with the 16/17 prescaler rated for input frequencies below 1.2 GHz. A 16/17 or an 8/9 prescaler can be selected for the 1.2 GHz RF synthesizers with the 8/9 prescaler rated for input frequencies below 550 MHz. Using a digital phase locked loop technique, the LMX237X can generate very stable, low noise control signals for UHF and VHF voltage controlled oscillators (VCO's). Serial data is transferred into the LMX237X via a 1.8V three wire interface (Data, Enable, Clock) compatible with low voltage baseband processors. Supply voltage can range from 2.7V to 5.5V. The LMX237X family features very low current consumption typically: LMX2370 - 6.0 mA @ 3V, LMX2371 - 5.0 mA @ 3V, LMX2372 - 4.0 mA @ 3V.