Hello all,
I am trying to make a solar charger such that solar cells will trickle charge a 18650 battery while the battery powers an arduino pro mini. This may be a long post but I want to explain my reasoning for the schematic.
When it comes to the parts: the main part is ofc the BQ25570 IC, there is also kind of an array of resistors used to set voltage divisions to set up V_OUT, overcharge voltage and MPPT tracking. I chose the values of the resistors by putting in desired values in an Excel sheet gotten from TI instruments here. The idea is using a set of jumper caps to set a specific MPPT ratio and also using the jumper caps on setting V_OUT and overcharge voltage.
For the capacitors were from reading the datasheet and using mostly typical values and the ones used in the solar application example.
Inductors were picked on the same principle. As a note, I am hoping to get a 3.6V output and around 12mA output.
Wasn't a long post after all but I would appreciate feedback on this and also if I need to clarify anything else.
Here is the schematic (do pls tell if quality is bad, I uploaded png):
I set it up as a 4-layer board. The Back copper layer is GND. The third layer is VRDIV and the second layer is VOC_SAMP. Here is the PCB routing on the 3D view (was unsure how to best show the 2D routing)
This is the image I mostly took inspo from for the schematic (it's in the datasheet as well):
Thank you for your time.
I am trying to make a solar charger such that solar cells will trickle charge a 18650 battery while the battery powers an arduino pro mini. This may be a long post but I want to explain my reasoning for the schematic.
When it comes to the parts: the main part is ofc the BQ25570 IC, there is also kind of an array of resistors used to set voltage divisions to set up V_OUT, overcharge voltage and MPPT tracking. I chose the values of the resistors by putting in desired values in an Excel sheet gotten from TI instruments here. The idea is using a set of jumper caps to set a specific MPPT ratio and also using the jumper caps on setting V_OUT and overcharge voltage.
For the capacitors were from reading the datasheet and using mostly typical values and the ones used in the solar application example.
Inductors were picked on the same principle. As a note, I am hoping to get a 3.6V output and around 12mA output.
Wasn't a long post after all but I would appreciate feedback on this and also if I need to clarify anything else.
Here is the schematic (do pls tell if quality is bad, I uploaded png):
I set it up as a 4-layer board. The Back copper layer is GND. The third layer is VRDIV and the second layer is VOC_SAMP. Here is the PCB routing on the 3D view (was unsure how to best show the 2D routing)
This is the image I mostly took inspo from for the schematic (it's in the datasheet as well):
Thank you for your time.