The SP5055 is a single chip frequency synthesiser designed for TV tuning systems. Control data is entered in the standard I2C BUS format. The device contains 4 addressable current limited outputs and 4 addressable Bi-Directional open collector ports one of which is a 3 bit ADC. The information on these ports can be read via the I2C BUS. The device has one fixed I2C BUS address and 3 programmable addresses, programmed by applying a specific input voltage to one of the current limited outputs. This enables 2 or more synthesisers to be used in a system.