> None of the tablets and phones I have tested are capable of even starting up on USB power alone: With a dead battery or removed battery they simply won't even power on.
This is likely to combat instability. A large sudden spike in current draw that has to be supplied by the wall wart a few feet of wire away from the PCB can trigger a brown-out. Especially with the usual quantity of decoupling capacitors, specced around having a large current source on tap much closer to the point of use.
This is likely to combat instability. A large sudden spike in current draw that has to be supplied by the wall wart a few feet of wire away from the PCB can trigger a brown-out. Especially with the usual quantity of decoupling capacitors, specced around having a large current source on tap much closer to the point of use.