A novel characterization technique for high speed I/O mixed signal circuit components using random jitter injection

Timing problems in high-speed serial communications are mitigated with phase-interpolator (PI) circuitry. Linearity testing of PI has been challenging, even though PI is widely used in modern high speed I/O architectures. Previous research has focused on implementing additional built-in circuits to measure PI linearity. In this paper, we present a cost effective PI linearity measurement technique which requires no significant modification of existing I/O circuits. Our method uses jitter distributions obtained from random jitter injected into the data channel. Two distributions are separately obtained using undersampling and sampling using PI. The proposed algorithm calculates the differential nonlinearity (DNL) from the difference of these distributions. Simulation results show that the average prediction RMS error for the DNL calculation is 0.31 LSB.