At X-ray synchrotron facilities, scattering experiments require detectors with a large sensitive surface, an high count rate capability, a large counter dynamics, a fast readout system and an adjustable energy threshold. X-ray pixel chip with adaptable dynamics (XPAD3) is a new pixellized photon detector based on hybrid pixel technology, which provides low noise data readout at high speed. It is designed in 0.25 mm IBM technology and contains 9600 pixels (130 mm  130 mm) distributed into 80 columns of 120 elements each. Its features have been optimized to fulfill a count rate capability up to 10 +6 photons/pixel/s, an high dynamic range over 35 keV, a very low noise of 130e À , and a threshold adjustment well below 4 keV. Fast data readout below 2 ms/frame is expected. To meet these requirements, an innovative architecture has been designed that makes possible the readout the circuit during acquisition while preserving the precise setting of the thresholds all over the pixel array. The XPAD3 circuit can be bump-bonded with Si, CdTe, or GaAs sensors to optimize its detection efficiency at high X-ray energies. XPAD3 detector modules will be tiled together to form the XPIX detector with a 8 cm  12 cm sensitive area. We present first results obtained using a single-chip prototype of the XPAD3 detector.