SLUSDV2A May 2020 – May 2021 BQ25798
In this scenario, both ACFET1-RBFET1 and ACFET2-RBFET2 are present. VAC1 / VAC2 is tied to the drain of ACFET1 / ACFET2, ACDRV1 / ACDRV2 is connected to the gate of ACFET1 / ACFET2. This structure is developed to support dual-input connected at VAC1 and VAC2. At POR, the charger detects both ACFET1-RBFET1 and ACFET2-RBFET2 present, then updates ACRB1_STAT and ACRB2_STAT to 1.
|PIN OR REGISTER FIELD||STATE|
|External MOSFETs||ACFET1, RBFET1, ACFET2, RBFET2|
|VAC1 pin||Connected to input source 1|
|VAC2 pin||Connected to input source 2|
|ACDRV1 pin||Connected to ACFET1/RBFET1 gate terminals|
|ACDRV2 pin||Connected to ACFET2/RBFET2 gate terminals|
0: ACFET1/RBFET1 Open (Path Disabled)
1: ACFET1/RBFET1 Closed (Path Enabled)
0: ACFET2/RBFET2 Open (Path Disabled)
1: ACFET2/RBFET2 Closed (Path Enabled)
0: Allow ACDRV1 or ACDRV2 on if all requirements met
1: Force ACDRV1 and ACDRV2 off
0: Force ACDRV1 Off
1: Turn ACDRV1 On if all requirements met
0: Force ACDRV2 Off
1: Turn ACDRV2 On if all requirements met
In dual input mode, the ACDRV automatically turns on the ACFET-RBFET of the path where a valid input is first presented, without host intervention.If the two inputs are presented at VAC1 and VAC2 exactly at the same time, ACFET1-RBFET1 with higher priority (port #1 is primary) is turned on while ACFET2-RBFET2 stays off (port #2 is secondary). EN_ACDRV1 is automatically set to 1. If a valid input is presented on the second path while the first path is already on with a valid input, the ACFET-RBFET of the second path remains off. If desired, the host may manually perform a switch between power paths by switching the values of EN_ACDRV1 and EN_ACDRV2. Both EN_ACDRV bits may be updated in a single I2C write operation to minimize the transition time. Note that programming EN_ACDRV1 = 1, EN_ACDRV2 = 1 at the same time to turn on both ACFET1-RBFET1 and ACFET2-RBFET2 is not allowed, and will be ignored by the charger.
To transition from one input to the other, the device first turns off the initially active ACFET-RBFET pair, waits until the VBUS voltage drops lower than VBUS_PRESENT, and then enables the new ACFET-RBFET pair. During this change over, the converter stops switching for a short period of time.
If two valid voltages are present at VAC1 and VAC2 and the source on the connected path becomes invalid because of VAC_UVLO, VAC_OV or IBUS_OC, the charger automatically swaps the input without any host engagement. Any time that the converter autonomously swaps the source paths, it will also update the EN_ACDRV1 and EN_ACDRV2 bits accordingly in order to indicate the active power path.
With only one valid input presented at either VAC1 or VAC2, the ACFET1-RBFET1 and ACFET2-RBFET2 can not be both turned off by setting REG0x13[7:6] = 00. Instead, the host should set DIS_ACDRV = 1 to force both ACFET-RBFET pairs off. With input sources present at both VAC1 and VAC2, the host can turn off the two ACFET-RBFET pairs by setting either REG0x13[7:6] = 00 or DIS_ACDRV = 1.