SLUSDU0 September 2019 BQ21061
The VINDPM loop prevents the input voltage from collapsing to a point where charging would be interrupted by reducing the current drawn by charger in order to keep VIN from dropping below VIN_DPM. Once the IN voltage drops to VIN_DPM, the VINDPM loops will reduce the input current through the blocking FETs, to prevent the further drop of the supply voltage. The VINDPM function is disabled by default and may be enabled through I2C command. The VIN_DPM threshold is programmable through the I2C register from 4.2 V to 4.9 V in 100-mV steps.
On the other hand, the DPPM loop prevents the system output (PMID) from dropping below VBAT + 200mV when the sum of the charge current and system load exceeds the BQ21061 input current limit setting. If PMID drops below the DPPM voltage threshold, the charging current is reduced. If PMID continues to drop after BATFET charging current is reduced to zero, the part will enter supplement mode when PMID falls below the supplement mode threshold (VBAT - VBSUP1). NOte that DPPM function is disabled when PMID regulation is set to battery tracking.
When the device enters these modes, the charge current may be lower than the set value and the corresponding status bits and flags are set. If the 2X timer is set, the safety timer is extended while the loops are active. Additionally, termination is disabled.