Hello,
I'm creating a new thread as the previous one i have created has been put as resolved but actually the problem is persisting. (Here is the link of the previous thread : e2e.ti.com/.../620416 )
I'm still facing an issue with my bq25570. Indeed, when it is in charging mode, that is to say when a voltage is applied on VIN, VOUT can falls downs in unregular way under 2V that makes my CPU to reset.
The following setup is implemented:
- The energy source is a solar cell : 0.42W - 3V
- The storage elements are two supercap of 35F (2.7V) put in series
- VBAT_OV = 5.04 V
- VOUT = 3.36 V
- VBAT_OK_PROG : 2.32 V
- VBAT_OK_HYST : 3.10 V
VOUT fall down most of the time when a radio frame needs to be sent but not necessary, it can also occurs when the CPU wakes up. (Just for your information, a radio frame will loads arround 50mA for arround 1 or 2 seconds or even more). When an instability has been triggered, it seems that the system stays unstable for a certain time ... The instability can stop by itself or as soon as i cover the solar panel .... Sometimes, the VOUT drooping can occur after several hour without issue ...
I have one board on which all is OK, it didn't reset for more than 20 days. and it continues running well and sending arround 60 radio frame each day.
I thougt that putting a capacitor of 100uF on VBAT pin would solve the problem, but it didn't, i have also tried to increase CSTOR and COUT up to 100uF but without success, it was even worse ...
Here is my schematics :
Here is my PCB :
Here is a photo of the board :
Here are some screenschots :
| VOUT (Yellow) and VSTOR (Blue) : | VOUT (Yellow) and VIN (Blue) : | VOUT (Yellow) and VRDIV (Blue) : |
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| VOUT (Yellow) and VBAT (Blue) : | VOUT (Yellow) and VBAT_OV (Blue) : | VOUT (Yellow) and LPBOOST (Blue) : |
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Regarding the PCB, maybe there is not enough via between the top VSS layer and the bottom VSS layer.
We have also noticed when we decrease VBAT_OV to 4.5V for example (instead of 5.04V), there is no more issue or instability ...
It has been several month now we are searching for a solution but without success. We are considering to use another IC now if we cannot resolve this issue :(
