Hello Kerr,
CHRG_DET H and L conditions depend on CHRG_POL.
If CHRG_POL is connected to GND, then CHRG_DET output pin is active low. Otherwise, when CHRG_POL is connected to VBAT then CHRG_DET output pin is active high.
To be precisely, when CHRG_POL pin is at GND then CHRG_DET is in active low open-drain mode with external RCHRGDET(100K) connected to VBAT. When CHRG_POL pin is at VBAT then CHRG_DET is in active high open-source mode with external RCHRGDET (100K) connected to GND. This pin is 5V tolerant.
Per Battery charging spec: In order for the Power Management Unit (PMU) to know if a portable device was attached to a charging port, the PMU would receive a signal from the PHY; it is recommended that the interface between the PHY and the PMU be an active low, open drain, charger detect signal, as shown in the following image.
Best regards,
Diego.
