The SP5655 is a single chip frequency synthesiser designed for TV tuning systems. Control data is entered in the standard I2C BUS format. The device contains 2 addressable current limited outputs and 4 addressable bidirectional 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 I 2 C BUS address and 3 programmable addresses, programmed by applying a specific input voltage to one of the current limited outputs. This enables two or more synthesisers to be used in a system.