Other Parts Discussed in Thread: TPS3779, BQ24075
Dear support team
I would like to build a battery charger incl. power path management with the BQ24078. As this chip does not feature an under-voltage protection (prevent discharging of the battery lower than 2.5V), I would like to add this feature with an additional voltage detector. Please consider the sketch of the proposed circuit:
Note the following comments:
- I added an inverter after the TPS3779. Like this, the SYSOFF Pin of the BQ24078 is LOW as long the detected battery voltage is above 2.5V (and thus the FET of the BQ24078 is on). Correct?
- The TPS3779 will be powered by a separate 3.3V buck-boost converter, which is connected to the BQ24078. In case of an under-voltage detection, the SYSOFF pin is driven HIGH by the TPS3779. As a consequence, the TPS3779 is not powered anymore. What would happen in this case? In my understanding, the BQ24078 would resume operation, the TPS3779 would again detect under-voltage and shut off the BQ24078. This would go forth and back and continues to drain the battery (?)
- Also I noted, that the charge voltage is 4.35V, is this correct? The charge voltage of our battery (and most Li-Ion batteries) is actually 4.2V though…
- Would you have any other solutions to propose?
Best wishes,
Lukas
