In this paper, a 360° wideband phase shifter with current limited vector-sum and digital calibration is presented to achieve high phase resolution and low amplitude error. The output phase is synthesized from quadrature vectors by variable gain amplifiers (VGAs) with current-digital to analog converters (I-DACs). Several VGA control algorithms are investigated to find trade off among phase error, amplitude error, and power consumption. A current limited vector-sum method is proposed to achieve low phase error, amplitude error, and power consumption, simultaneously. Quadrant selection is realized by the reconfigurable VGAs without extra switch circuit. Coarse- and fine-scaling of quadrature vector amplitude is accomplished by I-DACs with segments of different current weights. The phase non-linearity is calibrated using digital pre-distortion to further improve the phase error. To verify the mechanism mentioned above, a fully integrated 10-bit phase shifter operating at 3–7 GHz with current limited vectors is implemented and fabricated in a conventional 40–nm CMOS technology. It exhibits root mean square (RMS) phase error of 0.41°–1.67°, RMS amplitude error of 0.42–0.89 dB, and effective phase resolution of 1.406° (8-bit) from 3–7 GHz. The core circuit occupies 0.19 mm² and draws 11.4–16.2 mW from 1.1 V supply.