A hot-swap controller is a device or integrated circuit (IC) that manages the insertion and removal of circuit boards or components from a live system without interrupting the operation of the system or causing damage. Hot swapping is the process of replacing or adding components in a computer system without the need to shut down or reboot. It allows the removal of a USB peripheral device or interchanging SIM cards in smartphones without powering down the system. Hot swapping is used to change system configuration or repair a working system without interrupting its operation, providing convenience and avoiding delays.

Functions of Hot-Swap Controller

• Control Inrush current: As a hot-swap board is plugged into the system, the controller gradually charges the board’s capacitor to avoid a large surge of current and other malfunctions that may be caused by the insertion.
• Isolate Faults: The hot-swap controller isolates any faults that may occur on the inserted board from the rest of the system. It monitors faults such as overcurrent, overvoltage, and undervoltage conditions and responds by taking protective actions like disconnecting the faulty component or signaling an alert.
• Power Management: The hot-swap controller monitors power in every unit and determines when a redundant power unit should start functioning. A drop below a preset value will indicate a fault and automatically switch the system to the backup power unit without disrupting the load. It also regulates the sequence in which power is delivered to various components or sections of the board.
• Electrostatic Discharge (ESD) Protection: The hot-swap controller protects sensitive electronic components from damage due to ESD during the insertion or removal process. ESD protection circuits are integrated to safely dissipate electrostatic charges.
• Status Monitoring: The hot swap controller includes status indicators (e.g., LEDs) or interfaces with a system controller to convey information about the state of the hot-swapped component, such as power-good signals and fault status.

Hot-swap controllers enable the replacement or upgrade of components such as hard drives, power supplies, and network cards without shutting down the server. They are crucial for maintaining the continuous operation of network equipment, allowing for maintenance and upgrades without downtime. These controllers are also used in critical control systems, where uninterrupted operation is essential, permitting the replacement of faulty modules without system interruption.

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