Title says it: I'm working on building a high current USB charger for my devices so that I can integrate USB ports into my headboard. However, I'm having a few glitches.
- When I plug in a device, the voltage drops ~0.5V. Each device after drops it ~0.1V further per device. I have it up to 5.5V at the moment, and plugging in my devices will drop it to 5V. Yet it's charging my tablet just fine. Very fast actually even without declaring the current capability.
- My iPhone will not charge through this. I have a MAX14667 chip I am integrating, but was hoping I could get it to charge without it for testing purposes as they are small chips and pain in the butt to work with. Is this because I haven't declared the current capability with a resistor divider yet? The most I got is a "not supported" message from the iPhone.
- For the purpose of easy testing, I'm using a TI LMZ23605 module. However, for some strange reason the resistor values calculated by the TI site are not giving me 5V on either of the two modules I have prepped for a breadboard. Here is the schematic:
So my values are Rfbb = 1K, Rfbt = 5.6K + 352. This has given me 5.5V. Plugged in my tablet, dropped to 5V.