I have the BQ25798 IC on one of my project, it will charge the LiFePO4 battery but not Li-ion battery, as the LiFePO4 battery flat charge chart,
what are the voltage setup will be recommended for Trickle, pre-charge, CC, CV and recharge stage?
In addition, for a 3S configuration, what is Vsys range should be for a 5V/3.3V DC-DC converter load?
Nan Liu
Hi Nan,
The PROG pin resistor sets the converter switching frequency, default battery regulation voltage and default minimum system voltage at SYS. The defaults are relative to 4.2V LiIon x 1,2,3 or 4 so you will use the closest setting that is lower than your LiFePO4 regulation voltage. If this is for a 1S LiFePO4, I recommended setting for 1S 4.2V with /CE pin pulled high. Then the host can change the battery regulation voltage and minimum system voltage before pulling /CE pin low to enable charging. The charger automatically provides fixed 100mA trickle charge, I2C adjustable precharge (120mA default), adjustable CC (1A default), adjustable CV (default per PROG pin resistor). The voltage droop at BAT to trigger a recharge is set by the bits below:
after a deglitch time set by the bits below
in REG0x0A.
The SYS voltage output range is from the adjustable MINSYS setting in the register up to the battery regulation voltage.
In other words, the charger provides a minimum system voltage for a depleted battery and then follows the battery as it charges up to regulation.
Regards,
Jeff
