Techniques for programming trimming circuitry of a power integrated circuit without the need for separate programming pins are disclosed. According to a first aspect of the invention, there is provided a power supply controller IC with internal circuitry, a plurality of external connections, the IC further comprising trimming circuitry with no external connections to the IC other than via shared ones of the external connections. The shared external connections can comprise a first connection comprising a data input for receiving data for programming the trimming circuitry, and a second, different connection comprising a select input to select between a data receiving mode for receiving data from the data input and a programming mode for programming the trimming circuitry using the received data.