I found the link
https://www.analog.com/en/products/power-management/battery-management/coulomb-counter.html
however there is no further useful information.
You need at least 22 bits of analog conversion
which gives 0.000024 % accuracy - I dont see why.
That's for high dynamic range when the load varies.
Many devices alternate between high current and low current modes (active v. sleep mode). The
active current might be 100mA, the sleep current 5uA. If you want 1% accuracy for both cases
thats 21 bits or so...
However there's an easier way - use a diode shunt to give a logarithmic voltage reading representing
the current, makes for great dynamic range at the expense of accuracy (but estimating battery
capacity is a rough and ready thing anyway). 10-bit ADC is probably good enough then.
The main downside to using a diode in this way is that temperature correction may be needed for
reasonable performance as diode forward voltages depend on temperature as well as current.