So I wasn't thinking very hard when I designed a circuit to selectively power the analog portion of my design and ended up with this:
So I have a SOT-23 on the board where the FET is, with no place for a resistor on the gate/base terminal. A normal enhancement mode N-channel FET would not work here, since there is no way to bootstrap the gate. Alternatively, a P-channel FET would not work, since there would be no way to turn off the FET because the microcontroller can't drive the gate close enough to 5V.
I thought about using a BJT, but there is no space on the PCB for a base resistor. Is there any part that would fit into a SOT-23 footprint that acts as a load switch in this situation (I can mess with the pin settings on the GPIO pin from the microcontroller).
The uC is a LPC4337 with programmable pull-up and pull-down resistors. The (short circuit) drive current is 87mA source and 77mA sink. The pull down current is 93uA and the pullup current is -62uA.
The analog load is fairly complex to characterize, but it consists of a IBIS4-14000C image sensor 53mA peak @ 3.3V and 2 * WM8216 video ADCs with 118mA peak @ 3.3V each. The 3.3V is supplied through a dedicated LDO for the analog portion, and the peak current is about 300mA. The highest voltage requirement is the V_reset for the sensor, which needs 4V supplied from the 5V switched analog regulated down to 4.0V through a TPS76301 LDO (300 mV dropout voltage). Therefore, the switched analog supply should not drop below 4.3V. The other voltages have negligible current.