SWCS142 July 2018 TPS650861
PRODUCTION DATA.
The PMIC requires a step-up voltage from the 5-V input to 5.8 V for the VSYS supply. TI recommends keeping the VSYS near 5.8 V for optimization of the controllers.
Depending on the application use cases, the supply current to the VSYS can require from 40 mA with the drivers being supplied by the 5-V input to 440 mA with the drivers being supplied by the LDO5 and the LDOA1 being operated at max loading. This means that a charge pump may be used in some applications like the 5-V input but in others, a small boost may be required.
A Schottky diode from the 5-V input to the VSYS is recommended to ensure the VSYS is biased and the internal reference LDOs are on before the step-up regulator is enabled or fully ramped up. If the step-up cannot tolerate pre-bias condition then, 2 diodes may be needed to prevent the initial 5-V supply biasing the output of the step-up.