OPEN-LOOP CORRECTION OF DUTY-CYCLE ERROR AND QUADRATURE PHASE ERROR

摘要

A Phase Interpolator (PI) may be employed as a precisely-controlled delay element in a transmit path, for example in clock forwarded serial links. Methods and circuits are disclosed for estimating a delay needed to correct duty-cycle/and or phase errors of the received clock. These corrections or delta values may be transmitted back to the transmitter side, preferably expressed directly in terms of PI phase codes, for convenient adjustment in the transmitter clock circuitry. Various techniques also are disclosed for measuring and mitigating the effects on PI integral non-linearity.

主权项

1. A method for duty-cycle correction of a clock signal comprising:
receiving a clock signal in a clock-forwarded serial communication link; sampling the received clock signal over a selected number of samples to measure a duty-cycle of the received clock signal; estimating a delay for adjusting the received clock signal to achieve a desired duty-cycle using a phase interpolator; expressing the delay in terms of a phase code adjustment (Δ) compatible with a predetermined phase interpolator step size; and conveying the phase code adjustment (Δ) to a transmitter for adjusting the duty-cycle of the clock signal, using a phase interpolator, so as to achieve the desired duty-cycle of the received clock signal.