Performance Comparison of two Integrating-Mode Phase Interpolators

A phase interpolator is a device that can vary the phase of its output signal by interpolating two periodic input signals with a control input and is useful for applications such as fractional-N PLL, fully digital polar transmitters and sampling oscilloscopes. With this functionality, it closely resembles the working of a digital-to-time converter that controls time delay by a digital code. This paper shows a performance comparison in simulations regarding the integral non-linearity between two different types of phase interpolators. The topology used for the two PI’s consists of a 3-bit current-steering DAC with a capacitor and a reset path and has a full-scale delay of 1ns. It is shown that one of the PIs has a better INL peformance than the other PI where the peak value in INL is a factor 1.94 higher for the worst performing PI. Some INL remains for the best performing PI for which 31.67% of this INL is traced.