TI's Smart High Side Switches can be used to drive large bulk and hold-up capacitive loads that often go as high as 4 mF. Depending on the rise time at power-up, this load output capacitance can cause large inrush currents that are limited only by parasitic resistance and inductance’s present in wiring and interconnections. The inrush in some scenarios can exceed 100A. High currents such as this can potentially cause input voltage supply droop which can harm or cause malfunction in other circuits in the system.

To prevent these problems a Smart High Side Switch can be used to limit the current and reduce the inrush current by linearly charging the capacitive load. Inn order to effectively drive capacitive loads with a Smart High Side Switch it is necessary to understand the impact of thermal dissipation in the switch while it is current limiting as large power levels can be observed inside the device. A proper theoretical understanding of the charging process and practical understanding for the selection a Smart High Side Switch enables an engineer to design a proper output stage that will have safe and efficient capacitive load driving with minimized system costs.

In this section we will dive in-depth to the considerations that are required when driving capacitive loads. We will initially discuss a few applications where capacitive loads are present before looking at the system advantages of a Smart High Side Switch for inrush current limiting. After that we will investigate the thermal impact capacitive load driving has in a Smart High Side Switch and how to mitigate this in a system. Finally we will discuss the selection of an appropriate high side switch for a specific load profile.