The LTC4282 is a dual gate low voltage hotswap that is capable of protecting downstream systems by controlling inrush current and providing accurate and adjustable current limiting for short circuit protection. The LTC4282 is unique in its capable of operating in three distinct modes, each with its set of advantages:
The dual gate topology allows the LTC4282 to split current evenly between two parallel paths; reducing the stress on each MOSFET by half. Even with this topology moderate SOA MOSFETs are required and each rails needs to be optimized for Rdson. This topology works well in medium to high current applications.
Low Stress Staged Start Mode:
In LSSS mode, one gate is used as a trickle channel with its current limit set to a very low value (typically 10% or less of the load current). This channel is responsible to charge up the output capacitor to to the nominal value. Once this is completed the other gate, which is used as a bypass channel, turns on and allows the full load current to pass through to the output. This allows the bypass channel MOSFETs to be optimized only for RDS(ON) and does not require a high SOA as it turns off as soon as a transient event occurs. The timer is set to a very low value to protect these MOSFETs. This topology works well in high current cost sensitive applications which do not require ride through during transient events such as load step.
High Stress Staged Start Mode:
In HSSS mode, both channels share a single current sense resistor. One gate is designed as a high stress channel which conducts the full load current during transient situations such as turn on, input step, short circuit. The MOSFET used in the high stress channel needs to be optimized for SOA but not RDS(ON). The other gate is used as a bypass channel which only switches on during steady state conditions and hence the MOSFETs are only optimized for RDS(ON) and not SOA. This topology works well in high current cost sensitive applications which require ride through during transient events such as a load step.