VSINT supplies the SBC functions, in particular the voltage regulator VCC1, which is intended to supply the microcontroller
VS supplies the gate driver and it is also connected to the drain of the high-side MOSFETs of the external half-bridges.
Splitting VS and VSINT enables to buffer the VSINT voltage in case of voltage dips on VBAT, in order to keep the microcontroller supplied.
Otherwise if VSINT and VS are tied together, when VBAT drops, the possible high current drawn by the motor will rapidly discharge any buffer cap.
Instead, if VS and VSINT are split, when VBAT drops:
o VBAT decreases, the capacitor Cin5 is discharged by the motor current
o But diode Drev1 is reverse biased, and capacitor Cin2 can buffer the SBC supply (and Vcc1), without being discharged by the motor current.Show Less