I am designing a hybrid power supply. The system is such that it will house an LDO and a switching regulator as well. The system has long intervals of sleep mode. Every now and then it wakes up and transmits/receives data. Its the transmission/reception times that a lot of current is drawn and the SMPS kicks in.
I intend to make use of a system whereby the current consumed is measured and the relevant supply is switched. One of the ways I can do that is using a current sensing resistor. The current is measured using an ADC and we turn on/off relevant MOSFETs that channel power from the LDO/regulator.
Now, my concern is about the MOSFETs. The MOSFETs need to be very high speed as the power source must be switched from LDO channel to switching regulator.
What is the average switching time for a MOSFET ? Also, can I speed up the switching time of a MOSFET by manipulating the gate voltage ? I understand that gate capacitance is an important parameter here. Is my plan of action of using MOSFETs for this a good approach ? Kindly advice.