SLUSF18A October 2023 – December 2023 BQ25638
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
The device terminates a charge cycle when the battery voltage is above recharge threshold, the converter is in constant-voltage regulation and the battery current is below ITERM. Because constant-voltage regulation is required for termination, the device does not terminate while IINDPM, VINDPM or thermal regulation loops are active. After the charging cycle is completed, the BATFET turns off. The converter keeps running to power the system, and BATFET can turn on again to engage supplement mode. Termination can be permanently disabled by writing 0 to EN_TERM bit prior to charge termination.
When termination occurs, the status register CHG_STAT is set to 111, and an INT pulse is asserted to the host. Termination is temporarily disabled when the charger device is in input current, voltage or thermal regulation. Termination can be permanently disabled by writing 0 to EN_TERM bit prior to charge termination.
At low termination currents, due to the comparator offset, the actual termination current may be 10 mA-20 mA higher than the termination target. An optional snubber circuit can be added from the SW pin to ground, to improve termination accuracy at low currents. Suggested values for the snubber circuit are 28 Ω and 3 nF.
In order to compensate for comparator offset, a programmable top-off timer can be applied after termination is detected. When the top-off timer is enabled and termination occurs, the status register CHG_STAT is set to 110. The top-off timer follows safety timer constraints, such that if the safety timers suspend, so will the top-off timer. Similarly, if the safety timers count at half-clock rate, so will the top-off timer. Refer to Section 7.3.5.5 for the list of conditions. The host can read CHG_STAT to find out the termination status.
Top-off timer gets reset by any of the following conditions:
The top-off timer settings are read in once termination is detected by the charger. Programming a top-off timer value after termination will have no effect unless a recharge cycle is initiated. CHG_FLAG is set to 1 when entering top-off timer segment and again when the top-off timer expires.