4.1 Enhancements

It would be relatively easy to implement a power bypass by adding a bypass power switch between the input voltage and the supply to the load switching regulator. All that is needed is a common cathode Schottky diode pair. The common cathode supplies the switching regulator input. One anode goes to the battery and the other anode to the input voltage. When the input voltage is present, the diode from the battery is reverse biased and the switch pulls power from the input voltage. When the input voltage is not present, the diode from the battery forward biases, the input voltage reverse biases and the output switcher pulls power from the battery. The only downside is the slight reduction in efficiency due to the power loss in the diodes.

Another potential enhancement would be to offload the load current conversion to an external delta-sigma ADC for greater resolution in the coulomb counting function. Several good application notes are available on Microchip’s website that cover this option.