SLUA947A March 2019 – May 2020 BQ24072 , BQ24072T , BQ24073 , BQ24074 , BQ24075 , BQ24075T , BQ24076 , BQ24078 , BQ24079 , BQ24079T , BQ24230 , BQ24232 , BQ24232H , BQ24232HA
2 Configuring 1.2A Fast Charge
To configure the BQ2407x, a few calculations will need to be done to get the resistors that would be used to program the desired values. Parameters that need to be programmed include the input current limit RILIM, the fast charge current RISET, the fast charge timer RTMR, and in some devices like the BQ24074 where the termination current can be programmed, RITERM. Since the termination current depends on the fast charge current in the BQ24074, RITERM should be changed when RISET is changed to have the same termination current.
Figure 1. 1.2A Fast Charge Configuration - ILIM set to 1.5A with RILIM = KILIM / ILIM = 1610 / 1.5A = 1.07kΩ
- ICHG set to 1.2A with RISET = KISET / ICHG = 890 / 1.2 = 750Ω
- ITERM set to 0.05A with RITERM = (ITERM * RISET) / KITERM = (0.05 * 750) / 0.03 = 1.25kΩ
- Charge timer set to 6.65 hours; RTMR = (Time * 3600)/ (10 * KTMR) = (6.65 * 3600) / (10 * 48) = 49.9kΩ
- EN2 set High and EN1 set Low to set input current through ILIM
- KILIM, KISET, KITERM and KTMR are obtained from the data sheet