Application note; Detail considerations when using hot-swap controllers

May 04, 2015 // By Graham Prophet
Maxim Integrated has posted an application note, 5914, “Using the MAX15090/MAX15090A Hot-Swap Solution in Low-Voltage Applications for Resistive Loads”. The devices are hot-swap controllers designed for a 12V bus and have a unique current foldback feature that ensures the internal FET operates in the safe operating area (SOA) when driving large capacitive loads.

Maxim Integrated has posted an application note, 5914, “Using the MAX15090/MAX15090A Hot-Swap Solution in Low-Voltage Applications for Resistive Loads”. The devices are hot-swap controllers designed for a 12V bus and have a unique current foldback feature that ensures the internal FET operates in the safe operating area (SOA) when driving large capacitive loads.

This application note outlines a simple way to operate these parts at lower voltages when driving loads that are resistive in nature.

Hot-swap controllers must contend with both steady-state and startup conditions. In steady-state operation, the MOSFET used as the controlled switch element must be designed to operate above the maximum current load of the internal FET and maintain junction temperature below the rated maximum junction temperature.

The steady-state power dissipation is basically the product of the square of the load current and the R DS(ON).

PD = I LOAD2 × R DS(ON)

(Eq. 1)

Dynamic requirements such as startup must be considered when designing a hot-swap IC with integrated FETs. This is an important consideration when driving capacitive loads that serve as the energy reservoirs for downstream point-of-loads (POLs). The MAX15090/MAX15090A use a technique that monitors the V IN - V OUT difference and uses a current foldback technique to limit the current during startup, which will be discussed in greater detail.

Read the complete note at; www.maximintegrated.com/en/app-notes/index.mvp/id/5914