I'm designing a simple device with a single cell LiPo that I want to be chargeable from a single solar power cell. As I start to look through the data sheets, I'm seeing that the battery charging is typically done just by providing a constant voltage output to the battery.
For instance, LTC3106, page 19:
Or LTC3105, front page:
Note position of batteries in line with the load??
These circuits seem to be designed to charge the batteries in question by providing a constant 4.2V power to a single cell battery. Is this really safe? Is this equivalent to trickle charging? Everywhere I've read that a LiPo needs a very specific type of charging discipline, such as MCP73831 (which I use in all of my projects without issue.) For instance, is it actually safe to charge a single cell lipo with a constant-voltage, variable current source and no cut-off?
Can someone more familiar with battery chemistries and charging process help enlighten me? (PS: I am not EE-trained, I am a home hobbyist.)