The MC12181 is a monolithic bipolar synthesizer integrating a high performance prescaler, programmable divider, phase/frequency detector, charge pump, and reference oscillator/buffer functions. The device is capable of synthesizing a signal which is 25 to 40 times the input reference signal. The device has a 4bit parallel interface to set the proper total multiplication which can range from 25 to 40. When combined with an external passive loop filter and VCO, the MC12181 serves as a complete PLL subsystem.