I am looking to use the TPS2511 for a USB charging port. I want to test with TPS2511EVM but have two questions from looking at the eval board schematic.
1. Why is the input voltage limited to 20V? The TPS54240 looks like it is okay with input voltages up to 42V. I see there's a limit of 35V for C2. There also is a limit on the EN pin of 5V, which from resistor divider R8/R9 corresponds to input voltage of 25.6V. From this, it looks like I'd be safe running with a 24V input (which is what I'd like to do). Perhaps I'll modify the resistor divider to give a little more margin, but is there anything I'm missing?
2. Can you explain the implementation of nCS used in this evaluation board? From reading the TPS2511 datasheet and looking at the schematic, it seems the design is to bump up input voltage when charge current reaches more than half of the current limit. But why would input voltage need to be bumped up? The only thing I can surmise is it's to compensate for the 70mOhm impedance of the TPS2511, but this voltage drop difference from 500mA-1.5A is pretty low, especially considering TPS2511 says it can operate anywhere from 4.5-5.5V input.
