SLVSD02D March 2015 – June 2019 TPS65982
The system is design to either charge over Type-C or from the DC barrel jack. The TPS65982 detects that the DC barrel jack is connected to GPIOn. In the simplest form, a voltage divider could be set to the GPIO I/O level when the DC Barrel jack voltage is present, as shown in Figure 80. A comparator circuit is recommend and used in this design for design robustness, as shown in Figure 81.
This detect signal is used to determine if the barrel jack is present to support the 20 V PD power contracts and to hand-off charging from barrel jack to Type-C or Type-C to barrel jack. When the DC barrel jack is detected the TPS65982 at each Type-C port will not request 20 V for charging and the system will be able to support a 20 V source power contract to another device. When the DC Barrel Jack is disconnected the TPS65982 will exit any 20 V source power contract and re-negotiate a power contract. When the DC Barrel Jack is connected the TPS65982 will send updated source capabilities and re-negotiate a power contract if needed.
The PFET enable will be controlled by the DC barrel jack detect comparator depicted in Figure 81. This will allow the system to power up from dead battery through the barrel jack as well as the Type-C ports. Figure 83 shows the flow between changing from DC barrel jack charging and USB-PD charging. The example uses back-to-back PFETs for disabling and enabling the power path for the DC Barrel Jack. It is important to use PFETs that are rated above the specified parameters to ensure robustness of the system. The DC Barrel Jack voltage in this design is assumed to be 20 V at 5 A, so the PFETs are recommended to be rated at a minimum of 30 V and 10 A of current.
The TPS65982 in this design also provides the GPIO control for the PFET gate drive that passes the DC Barrel Jack Voltage to the system. Figure 83 shows the flow between changing from DC Barrel Jack charging and Type-C PD charging.