1. On page 13 of the datasheet, the VREG5 bypass is connected to PGND. On page 17 the layout example shows the bypass is to SGND. Which is correct?
2. Is there a tool to simulate and generate bode plot of the design with TPS54494? The datasheet doesn't give cutoff frequence and phase margin with the recommended component values and the range is too loose. Warm fuzzy is not good.
Xiaochen,
I have seen VREG5 connected to both grounds in the past. The official EVM has the VREG5 capacitor tied to PGND, but it is tied directly adjacent to the single point connection of SGND to PGND. Other devices using that same DCAP2 control use PGND as well. So I would recommend PGND as shown in the EVM Users Guide:
TPS54494 uses DCAP2 control. Generally, there are no frequency domain models available. Table 1 in the datasheet gives the recommended component values for various output voltages, including the output filter components. As long as you follow those recommendations, you need not worry about stability issues.
