Digital delay line calibration with duty cycle correction for high bandwidth memory interface

Abstract

Embodiments include a memory device with an improved calibration circuit. Memory device input/output pins include delay lines for adjusting the delay in each memory input/output signal path. The delay adjustment circuitry includes digital delay lines for adjusting this delay. Further, each digital delay line is calibrated via a digital delay line locked loop which enables adjustment of the delay through the digital delay line in fractions of a unit interval across variations due to differences in manufacturing process, operating voltage, and operating temperature. The disclosed techniques calibrate the digital delay lines by measuring both the high phase and the low phase of the clock signal. As a result, the disclosed techniques compensate for duty cycle distortion by combining the calibration results from both phases of the clock signal. The disclosed techniques thereby result in lower calibration error relative to approaches that measure only one phase of the clock signal.