USB mini ports for charging

[CraigHB]

Not that much to it really. Just implement the charging circuit as shown in the typical application schematic on page 19 of the MCP73833 data sheet. Pair a couple of small signal N-channel MOSFETs in series with the PROG resistor ground connection. Connect the input gate of the MOSFET pair to the atomizer high side with a pull-down. What that does is float the PROG pin when the atomizer is energized which puts the controller in standby. When the atomizer is de-energized, the controller returns from standby and resumes charging. I use an MCU to provide a delayed control signal which avoids transients due to the converter, but for an unregulated mod, there should be no issue with using the atomizer supply to provide a control signal.