TPS53015: Questions about Figure 18 of the datasheet

Hello Hirano, , 

Question1: 

• Select an R2 value between 10 kΩ and 100 kΩ and use Equation 11 to calculate R1.
• R5 is the BST  resistor use ~5.11ohms 
• R9 and C12 are the snubber circuit. You can use the same value as the EVM and the datasheet, they are already been calculated for you. If you wnat to know how they are calculated, please look into this  

Power Tips: Calculate an R-C snubber in seven steps - Power management - Technical articles - TI E2E support forums

Question2:

R7 and D1 that is voltage clamping circuit to protect the device from reverse  voltages on the SW pin to GND.  The SW is rated NOT to go outside the abs max of -300mV to 30V. 

SO any reverse voltage outside that range risk damaging the device, and thus that circuit is recommended to clamp the SW voltage. For D1, we typicall look into the reverse voltage the forward voltage that we want to protect against  

Thanks! 

Tahar