Simulation

OTA

Figure 1 shows that our two-stage OTA has an open loop gain of 74dB and GBW of 30MHz under the TT corner.


Figure 1. OTA simulation


System stability

Figure 2 shows our whole system stability simulation. Because the comparator and driver are non-linear systems, we cannot simulate phase margin with these components. So, we model the comparator and driver as a vcvs with some delay, and the gain of the vcvs is VDD/Vm, Vm is the Vp-p of the triangle wave. Then, the phase margin of the system loop can be simulated at about 85.3 degrees.

Figure 2. System stability testbench


Figure 3. System stability simulation


Triangle wave generator

Figure 4 shows our 500kHz triangle wave generated by the triangle wave generator, and Vp-p is about 1.3V.


Figure 4. Triangle wave simulation

By changing the Iref, we can easily change the triangle wave frequency from 400 kHz to 600 kHz


Figure 5. Triangle wave frequency vs. Iref


Non-overlapping generator

Figure 6 shows the relationship between dead time and Iref in the non-overlapping generator. By changing the Iref, we can tune the dead time from 10ns to 45ns.


Figure 6. Deadtime vs. Iref


Top-level simulation

The end-to-end simulation results are shown below. The input sinusoid wave is successfully reproduced at the output.


Figure 7. End-to-end simulation


Back to top