When an input source is present at
VBUS, the device checks the input source voltage to turn on REGN LDO and all the
bias circuits. It detects and sets the input current limit before the buck-boost
converter is started. The power up sequence from input source is as listed below:
- The device begins the POR sequence when VVBUS
> VVBUS_UVLOZ if there is a direct path from input to VBUS, or
otherwise when VAC1 or VAC2 >
VAC_PRESENT.
- 5 ms (typical) after a valid
voltage is first present at either VBUS or VAC1/VAC2 pins, the charger
starts the ACFET-RBFET detection, reads the resistance at PROG pin, and then
configures the charger power on reset (POR) default register settings
accordingly.
- If ACFET-RBFET are detected on the input source pathway,
the corresponding ACDRV turns on the pair.
- 20 ms (typical) after valid
voltage voltage presence, the I2C registers become accessible to
the host.
- As soon as VVBUS > VVBUS_UVLOZ (in
step 1 or after step 3), VBUS_PRESENT_STAT is set to 1. 150 ms (typical)
later, REGN is turned on.
- Once REGN is on, the charger starts the poor source
detection. After a good input source is detected (typically 30 ms if there
is no retry), PG_STAT is set to 1, then the ADC reads the ILIM_HIZ pin
voltage and VBUS voltage and updates the IINDPM and VINDPM registers
accordingly.
- When the poor source detection completes, the charger
performs D+/D- detection and updates the VBUS_STAT and IINDPM registers
accordingly.
- 30 ms (typical) after the D+/D- detection completes, the
converter starts switching to power SYS and charge the battery.