The PG pin goes
LOW to indicate a good input source when:
- VBUS above
VVBUS_UVLO
- VBUS above battery
(not in sleep)
- VBUS below
VACOV threshold
- VBUS above
VPOOSRC (typical 3.8 V) when IBADSRC (typical 30 mA)
current is applied (not a poor source)
- Completed Section 9.3.2.3