Tool/software:
Hi,
So I am using the BQ25792 IC to charge in this case, a 3.3V LiFeP04 cell with VREG at 3.6V I am hoping to charge it at CC of 3A (this is what I set it to).
I am using I2C to configure the charger and it seems to be working except that when I plug in a flat cell (say 2.4V ) the CC phase lasts for about 10 seconds and after that the Charge current appears to be dropping pretty fast from 3A to 1.4A (effectively tapering away). This is happening before VBAT has reached VREG; It's almost as though CC- fast charge phase is skipped entirely? Charging status now says "Taper Charge" where it sort of stays there for a while, while charging and its charging at 1.4A.
This is not what I expected, I was expecting a slightly longer 3A CC phase (atleast longer than 10sec) until the VBAT reaches 3.6V (the regulaion voltage) and only after this voltage should the charger go into "Tape Current" and eventually "Termination Current!. It's like the IC chooses its own CC - Charge Current ?
When configuring the IC via I2C I disable the watchdog first, set my VBAT and then the Charge Current. Below is my screen grab for when IC is charging . Is there a know issue with this or I am just blind and not reading my datasheet well. Many thanks for your help!
