3 Charging Current Issue Caused by Ground Shift

Apple spec provides the provision of port voltage requirements for lightning accessories and non-lightning accessories. No matter lightning or non-lightning accessories, the accessories port voltage should not be below specific threshold. If below specific port voltage, with lower terminal voltage, charging current will be smaller.

USB2.0 specification also makes provisions that the related ports voltage cannot be out of specific range ^[2].

Comparing Figure 3 with Figure 4, without and with additional resistor added, the charging current falls from 3A to 2.6A due to the voltage drop.

TPS2583x-Q1 and TPS2584x-Q1 integrate cable compensation function that can compensate the port voltage of accessories to required range ^[3].