The SP5668 is a single chip frequency synthesiser designed for tuning systems up to 2.7GHz. The RF preamplifer contains a divide by two prescaler which can be disabled for applications up to 2GHz so enabling a step size equal to the comparison frequency up to 2GHz and twice the comparison frequency up to 2.7GHz. Comparison frequencies are obtained either from a crystal controlled onchip oscillator or from an external source. The device contains three switching ports, P0 P2, together with an 'inlock' flag output. Various test modes including varactor disable and charge pump disable are also included.