ADM6819/ADM6820,datasheet,pdf(

The ADM6819 and ADM6820 are simple power supply sequencers with FET drive capability for enhancing N-channel MOSFETs. These devices can monitor a primary supply voltage and enable/disable an external N-channel FET for a secondary supply. The ADM6819 has the ability to monitor two supplies. When more than two voltages require sequencing, multiple ADM6819/ADM6820 devices can be cascaded to achieve this. The devices operate over a supply range of 2.95 V to 5.5 V.
An internal comparator monitors the primary supply using the VSET pin. The input to this comparator is externally set via a resistor divider from the primary supply. When the voltage at the VSET pin rises above the comparator threshold, an internal charge pump on the GATE output enhances the secondary supply FET.