Two functions unique to the high-side switch controllers are input protection and circuit breaking. For high-current input protection, high-side switch controllers sit at the output of a DC/DC converter or battery. Here, high-side switch controllers provide inrush current control and either short circuit protection (in the forward direction) or reverse current blocking, depending on the configuration. In the short circuit protection configuration, the overcurrent response type is latch-off and requires MCU intervention to turn the device back on. If a system requires both reverse current blocking and reverse short-circuit protection, one can combine a high-side switch controller and an ideal diode controller. Or, alternatively, use an ideal diode controller which has both features integrated. Both ideal diode controllers and high-side switch controllers are common choices for automotive input power protection because they offer high current capability and automotive AEC-Q100 qualification. Devices designed for input protection, like ideal diode controllers and hot-swap controllers, prioritize a stronger sink current to enable fast turn-off. High-side switch controllers often feature both strong source current and strong sink current, enabling their use for both input protection and output protection. For lower-current input protection applications, especially in industrial or enterprise applications, eFuses (integrated hot swaps) are more common solutions due to their compact size and power density advantage.

Table 2-3 summarizes the key differences between a high-side switch controller and ideal diode controller. To learn more about ideal diode controllers, see Basics of Ideal Diodes. Similar to the input protection function, high-side switch controllers can also perform circuit breaker functionality. For a DC/DC circuit breaker application, one can use two back-to-back FET high-side switch controllers on either side of the DC/DC converter. In this configuration, the high-side switch controllers control inrush current, manage overvoltage conditions and block current both upstream and downstream from the DC/DC converter.

Due to the bi-directional nature of this application, high-side switch controllers with bi-directional current monitoring and I²T-based short-circuit protection offer optimal protection. For circuit breaker functionality in a battery management system (BMS), one can use a high-side switch controller on the positive battery rail. A high-side switch controller with back-to-back FETs allows independent control of the charge and discharge paths. Additionally, in this BMS disconnect switch configuration, high-side switch controllers offer low quiescent current, reverse polarity protection (input and output) and current sensing. Automotive DC/DC and BMS circuit breaker applications are typically high-current (around 150A with 1kA peak) and thus require external-FET designs.

1. In on-state, high-side switch controllers can detect reverse current and signal the MCU to act, but they do not have an integrated protection scheme.
2. Available only in select devices
3. Current limiting clamps the output current at a specific value; the value can be programmable or fixed. I²T protection turns off the output current according to a specific current-time profile