Hot-Swap Circuits with Inrush Current Limiter

 

To provide continuous current sensing and limiting, this hot-swap circuit uses a PNP transistor and a current sense resistor of 0.333R. When input power is applied, current flows through R1 and Q1 and into the load. 

Current flowing through R1 generates the VBE bias voltage for Q2. If the current is sufficient to bias Q2 ON, Q2 reduces Q1's gate-source voltage, limiting the current to the load. A Zener diode is used to prevent overvoltage in Q1 and VCE breakdown in Q2.

Alternatively, a chipset solution from Maxim could be used. The MAX4370 is a circuit-breaker integrated circuit designed to provide protection in hot-swap applications using Maxim's DualSpeed/ BiLevel detection. 

The chip offers many features in a small package, and it requires few external components. The circuit offers inrush-current limiting and dual overcurrent fault protection, which consists of a fast response from the MAX4370 for high-amplitude circuit faults and a slow response for low-amplitude disruptive overcurrent conditions.