Other Parts Discussed in Thread: BQSTUDIO
Using BQ25895MRTWR with optional 900mA to 1000mA load on SYS. I've tried to configure V(sys_min) via SYS_MIN in REG03 to 3.7V (REG03==0x3E). My trouble is that when the V(battery) is low, such as 3.4V to 3.5V, and I turn on that optional 900mA to 1000mA load, the SYS voltage falls below the configured 3.7V, down to about 3.2V to 3.4V. Relative to V(bat), V(sys) is a little above it, but not as far above it to be the desired V(sys_min) of 3.7V. This situation persists for several seconds until my optional load turns itself back off due to insufficient voltage. It needs at least 3.5V. V(sys) = V(sys_min) = 3.7 volts would satisfy that. But V(sys) has fallen below that.
I've tried different BQ25895MRTWR register configurations, but haven't been able to improve the situation. I've attached a debug view of the BQ25895MRTWR registers during that several seconds of V(sys) < V(sys_min). One thing I notice is AllRegs[17] = REG11 = 0x90. I read this to mean the BQ25895MRTWR thinks V(bus) = 4.2V. I checked with a volt meter directly on pin 1, which remains at least 4.97V for the duration of this problem. (I used a scope for other measurements, to get dynamic info, but was too difficult for this measurement. The problem seems to be steady state, so I think the volt meter reading should be reliable and sufficient.) I wonder if the BQ25895MRTWR is giving up on maintaining V(sys) >= V(sys_min) because it thinks V(bus) has fallen too low. I did try setting AllRegs[13] = REG0D = 0x80 to avoid VINDPM, but the chip reset it to 0x13.
Below is a screenshot of all the BQ25895MRTWR registers during this steady state situation for several seconds of optional load turned on (900mA to 1000mA) and V(sys) < V(sys_min).
Thanks VERY much for your assistance.
