Patent ID: 8446198

Claim:
A phase interpolator comprising: a variable delay circuit to rotate phase of an input clock to generate a phase rotated signal; wherein the variable delay circuit comprises: a first variable delay circuit to rotate phase of the input clock in a first time period to generate and provide a first phase rotated signal as the phase rotated signal; and a second variable delay circuit to rotate phase of the input clock in a second time period to generate and provide a second phase rotated signal as the phase rotated signal; a controller, the controller generating a first control signal, enabling generation of the first phase rotated signal and the second phase rotated signal using a second control signal and generating the second control signal using a calibration circuit, the calibration circuit comprising: a first plurality of variable delay circuits coupled in a series connection; a second plurality of variable delay circuits coupled in a series connection, the second plurality of variable delay circuits being in parallel connection with the first plurality of variable delay circuits; and a detecting unit coupled to the first plurality of variable delay circuits and to the second plurality of variable delay circuits to detect a crossover between outputs of the first plurality of variable delay circuits and the second plurality of variable delay circuits, and to determine the second control signal based on the crossover; a delay locked loop coupled to the variable delay circuit to generate a plurality of phase shifted outputs, the delay locked loop comprising a plurality of delay elements, each delay element comprising: a multiplexer that is configurable using the first control signal to output one of the phase rotated signal and a phase shifted output of the plurality of phase shifted outputs, and a delay cell coupled to the multiplexer to delay one of the phase rotated signal and the phase shifted output to generate another phase shifted output of the plurality of phase shifted outputs.