power management for ruggedized, high performance IoT

requirements
- high output current (at least 10A + derate)
- range of output voltages from 5V to 24V
- maximize usage of battery capacity
- efficient operation
- provide safe, robust, predictable power to output

output profile
most of the devices are sensors with batteries so they follow a typical IoT power profile:
- moderate (>10mA) or high current (>1A) current during transmit
- low (1mA) very low current (100uA) all other times

output operating conditions
all topologies assume some time of switch or protection device on the output to provide some kind of control for:
- surge current or overvoltage protection at the output
- undervoltage and overvoltage at the input
- overcurrent protection
- slow start
- software control or hot plug control
- must operate with a high impedance source (e.g. a Li-Ion battery) which will dip during high current pulses

In addition the devices must be very efficient, consuming energy on the order of 1% (or worst case 10%) of the load. In practice this is difficult to achieve with OTS load switches because they typically consume several mA _or_ do not operate over the current or voltage ranges required.

possible topologies
with that in mind here are some possible concepts

before the output controller
- undervoltage boosting controller: this controller normally operates as a load switch but when voltage sags at the input (e.g. when customer sensor transmits) a boost controller with fast startup holds up the output voltage
- supercap ORed to battery to provide a lower impedance source during brownouts
- lower the impedance of the battery pack, remove intermediate sense resistors and control FETs

after the output controller
- a load switch (from main battery) ORed with a battery at the output. This would only work if Z_output_battery << Z_input_battery. And you'd have to maintain two batteries
- a load switch (from main battery) ORed with a supercap at the output. This might work better esp if controller electronics for the supercap can be avoided
- to what extent can ceramic or poly caps help?
- hot power supply on standby... like a gas powered plan on the grid but those are slow and I suspect this would be too
- regulate the output: just include a fixed output with a buck, boost, pass-through boost or buck-boost. There are some devices with pretty good efficiency at low currents (although not all support 10A outputs)

controllers
- OTS load switch: nothing in the Iq, voltage and current we need
- OTS "other": a few options exist, often for different reasons (like an automotive cold crank holdup from ADI)
- MOSFET: could work, single or back to back
- MOSFET driver: with MOSFETs
- ideal diode controller with back to back FETs
- load switch controller with external FET or back to back FETs
- power prioritizer (e.g. LTC4417)
- a combination of regulators and ORing/prioritizer

other
- vendor collaboration. controls to enable/disable the sensor or to have an interrupt could be utilized

All of these are subject to analysis and benchmarking.