# Analysis of Pre-Driver and Last-Stage Power--Ground-Induced Jitter at Different PVT Corners
## 3 Jitter Analysis under PVT Corners: Simulation Setups and Results
### Induced litter: Pre-Driver vs. Last Stage  
This study carried out an experiment to investigate the impact of the separate PGSV variations at the pre-driver or the last-stage supplies on the output jitter, as shown in Figure 4. Firstly, two different signal tones are applied to the pre-driver power supply \(v_{dd}(t)\) and ground supply, \(v_{ss}(t)\). These voltage sources are applied on the dc voltage for each corner, while the last stage is biased with a constant dc voltage source, as shown \begin{table}
\begin{tabular}{c c c} \hline \hline
**Corner** & \(\mathbf{V_{DD}/V_{DDQ}}\) & **T** (\({}^{\circ}\)**C**) \\ \hline SS\(-\)40 & \(-\)10\% \(V_{DDNom}\) & \(-\)40 \\ \hline SS125 & \(-\)10\% \(V_{DDNom}\) & 125 \\ \hline SS25 & \(V_{DDNom}\) & 25 \\ \hline FF\(-\)40 & \(+\)10\% \(V_{DDNom}\) & 125 \\ \hline FF125 & \(+\)10\% \(V_{DDNom}\) & \(-\)40 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Different PVT corners used to evaluate the PGSIJ via transient simulations of IO buffer circuit configurations. Figure 4: Simulation setup used to evaluate the impact of PGSV variations independently connected at the (**a**) pre-driver or (**b**) driver’s last stage. Figure 5: Simulation setups used to evaluate the p2p eye jitter. (**a**) two-tone voltage noise applied to the shared PG rails. (**b**) two-tone voltage noise applied the decoupled PG rails. in Figure 4a. Moreover, the same noise sources described above are used at the driver's last-stage terminals, \(v_{ddq}(t)\) and \(v_{ssq}(t)\), while the pre-driver stage is biased by constant dc sources, as presented in Figure 4b. Table 2 presents the different noise parameters, frequency, and amplitude values used in this setup. The simulation results of the p2p eye jitter, along the with eye width (EW) and eye height (EH) openings, are reported in Table 3. Eye measurements are determined between a 40% and 60% eye boundary time crossing and 20% and 80% of the amplitude thresholds, respectively. This result clearly shows that, for this IO buffer topology, the PGSIJ difference between the pre-driver and last stage is \(\sim\)10 ps at the slow-slow (SS\(-\)40 \({}^{\circ}\)C) corner ((\(V_{DD}=V_{DDQ}=2.97\) V, T = \(-\)40 \({}^{\circ}\)C). Therefore, the design engineer should consider if this analysis is carried out by means of behavioral models extracted or generated based on the IBIS or its power-aware version that shows several shortcomings in capturing PGSIJ by the pre-driver's supply \(V_{DD}/V_{SS}\) domains, because they are kept constant during device characterization and model extraction [14; 15]. The numerical results of the p2p eye jitter, which are reported in Table 3, confirm that the pre-driver PGSIJ can be as important as last-stage jitter. The percentage of the jitter distortion with respect to the unit interval (UI = 1/data rate) is added to demonstrate the jitter contribution in the eye timing margin difference between the SS\(-\)40 \({}^{\circ}\)C corner (i.e., \(\sim\)12%) against the fast-fast (FF)\(-\)40 \({}^{\circ}\)C (i.e., \(\sim\)5%). Although IO buffer design technology and circuit architecture can be different from the studied case, which may lead to different jitter numbers, considering PGSIJ by the pre-driver is as important as that induced by last-stage P/G rails. It is worth noting that the P/G supply noise of the pre-driver mainly induces jitter distortion, whereas the P/G supply noise of the last-stage inverter introduces both jitter and amplitude distortions, as is illustrated in Figure 6, where both eye plots are compared at the worst-case corner. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Setup** & \multicolumn{3}{c}{**Setup of Figure 4a,b**} \\ \hline
**Supply** & \(v_{ddq}(t)\) or \(v_{ddq}(t)\) & \(v_{ssq}(t)\) or \(v_{ssq}(t)\) \\ \hline
1 st tone & \{0.2 V, 800 MHz\} & \{0.15 V, 1300 MHz\} \\ \hline
2 nd tone & \{0.13 V, 1700 MHz\} & \{0.18 V, 900 MHz\} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: PGSV settings of setup Figure 4.