The TPS25820/21 supports two Type-C current advertisements as defined by the USB Type-C standard. Current broadcast to a connected Sink is controlled by the CHG pin. For each broadcast level the device protects itself from a Sink that draws current in excess of the port’s USB Type-C Current advertisement by setting the current limit as shown in Table 3.
|CHG||CC CAPABILITY BROADCAST||CURRENT LIMIT|
|0||STD (500 mA for USB 2.0 port)||1.67 A|
|0||STD (900 mA for USB 3.1 port)||1.67 A|
|1||1.5 A||1.67 A|
Under overload conditions, the internal current-limit regulator limits the output current on the OUT pin as shown in the Electrical Characteristics table. When an overload condition is present, the device maintains a constant output current, with the output voltage determined by (IOS x RLOAD). Two possible overload conditions can occur. The first overload condition occurs when either: 1) input voltage is first applied, enable is true, and a short circuit is present (load which draws IOUT > IOS), or 2) input voltage is present and the TPS25820/21 is enabled into a short circuit. The output voltage is held near zero potential with respect to ground and the TPS25820/21 ramps the output current to IOS.
In either case the TPS25820/21 will limit the load current to IOS until the overload condition is removed or the device begins to thermal cycle. This is demonstrated in Figure 16 where the device was enabled into a short, and subsequently cycles current off and on as the thermal protection engages.