Hello,
My customer already has device with BQ24295.
Now they want to implement version of device, which can work without accumulator battery.
As I found on e2e in this case BQ24295 will going sleep and waking up 20 times per second. As result any changes in configuration will reset on power-on.
There we have another one aspect of question.
When we set CHG_CONFIG = 1 (charge enabled) we got next oscillogram on SYS:
When charge disabled (CHG_CONFIG = 0) we'll got:
In first case we got average voltage about 4.29 V with ripples. In second - 3.83 V without ripples.
As I understand the ripples are the result of switching half-bridge (HSFET + LSFET).
In second case 3.8 V it's a voltage from REGN LDO, but I'm not sure about it because I can't found path from REGN LDO to SYS output.
Generally as I understand when battery disconnected and charge disabled we should got 0 V on SYS. But we got 3.83 V. I can't find an explanation for it.
But at the same time this behavior are OK for our application with one refinement - we want voltage on Vout higher that 4 V without ripples. So we should disable charge and raise the voltage. But I don't understand how to set up VSYS in this mode.
Finally there are 2 questions:
- It's possible to got voltage above 4V on SYS pin without battery?
- How to configure BQ24295 into this mode properly?