The current amplifier or the voltage amplifier is called into action during overcurrent or overvoltage conditions, appropriately limiting the output. In the case of an overvoltage, the load circuit continues to operate, with little more than a slight increase in supply voltage depending on the feedback setting. The load circuit may continue operating if, in the case of a current overload, sufficient output voltage is available. The timer capacitor ramps up whenever output limiting occurs, regardless of the cause. If the condition persists long enough for the timer pin to reach its first voltage threshold of 1.25V, the fault pin goes low to give early warning of impending power loss. Once the 1.35V second fault threshold is reached, the timer shuts down the MOSFET and waits for a cool-down interval before attempting to restart. Another feature of the LT4356 is the spare amplifier which may be used as a power good comparator, input voltage monitor or low dropout linear regulator. For the LT4356-1 and LT4356-3, pulling the Shutdown pin low results in a shutdown of all functionality with a supply current of only 7µA. In contrast, the LT4356-2 version keeps the auxiliary amplifier and internal reference active during shutdown with a shutdown current of 60µA. By configuring the auxiliary amplifier as a low dropout linear regulator, the LT4356-2 can be used for applications that require a keep-alive supply voltage for vital functions while the main system has been shutdown.