I'm planning a project that will use an alkaline battery (I can't use a lipo battery for this use-case) with a 5v step up converter to power a TinyZero processor.

Looking at the schematic, it looks like if I remove U2 (MCP73831) from the TinyZero board, that I should be able to plug in the 5V from the step-up converter into the board, and everything should work. It looks like Q1 would protect the battery from power coming from USB.

Is this correct? What about VBATT coming in through R8 to AD4? Is it ok to have 5~5.5V here?

Thanks!

Hi- yes, ignoring U2, operation is safe with 5V on the battery input, including R8(1M resistor will pull up to the internal protection diode on AD4). With U2 in place, you should not have problems(it's above 4.2V, so it will not try to charge, but below 6V so it shouldn't cause damage), but the datasheet does not specify operation for this condition(5v on VBAT) so it would be safest to remove it.

Thanks,
Ben