The SN761681 is a synthesized tuner IC designed for TV tuning systems. The circuit consists of a PLL synthesizer, three-band local oscillator and mixer, 30-V output tuning amplifier, four NPN band-switch drivers, and is available in a small-outline package. A 15-bit programmable counter and reference divider are controlled by I2C bus protocol. Tuning step frequency is selectable by this reference divider ratio for a crystal oscillator.