Impulse-radio-UWB is the ideal air interface for low power wireless applications especially when they require ranging capabilities. This paper presents a complete UWB transceiver system, including acquisition and ranging protocols. The system is fully reconfigurable in terms of bandwidth, data rate, processing gain, acquisition protocol and ranging accuracy, in order to fulfill the needs of the application with minimal energy consumption. The complete system is demonstrated by measurements on an IR-UWB transceiver platform built around 3 fully integrated CMOS chips. The transceiver system achieves a data rate up to 50 Mbps and a ranging error with a root mean squared error of less than 10 cm while consuming 31.7 mW. The IC implementation allows to fully validate the power/flexibility trade-off that can be achieved with integrated solutions.