nPM1300 hardware options for solar charging

[oc123]

Hello,

We are currently evaluating the nPM1300 as a key component on one of our new designs. This design must support both USB and solar charging using relatively low power solar cells with maximum power voltages and maximum power currents of ~4.5V and 50mA-200mA respectively. 

For the nPM1300 to work as a solar charger, it cannot try to draw more charging current than the solar cell can supply, otherwise the input voltage (from the solar cell) collapses. This is the behaviour we are currently seeing with the nPM1300 set to charging current 32mA when our solar cell (which acts as the input voltage source to the nPM1300) cannot supply the 32mA charging current that the nPM1300 is trying to draw. 

Do Nordic have any suggestions on how we could achieve this goal using the nPM1300? If solar charging support has even been discussed for this chip? If there is a firmware workaround that exists? Or, equally, if there is any hardware design that Nordic would suggest to achieve our goal and allow for dynamic regulation of the current drawn by the nPM1300 when the solar cell cannot supply the charge current requested by the nPM1300?

Thank you in advance,

Odhrán

[ChrisRu]

Hi,

I have an evaluation done too with a Solar-panel and a 1000mAH LiPo using a customized board.
Pitfall 1:
When the Sun is bright the floating voltage rose over the cut off Voltage and the nPM1300 protection hits
Pitfall 2:
When charging the current-microamp = <100000>; must set below the threshold where voltage drops below the 4.4V

Pitfall 1 solution. We add a diode in the power path which cuts 0.7V from the floating voltage (e.g. 5.6V(float) - 0.7 = 4.9V) not trigger the protection.

With this config we was able to have good charging setup.

Green, is the nPM1300 Blue, conventional solar charging module always charging.

Hope that helps.

Chris