SLVSF02D March 2019 – May 2020 TPS23881
Hardware classification (class) is performed by supplying a voltage and sampling the resulting current. To eliminate the high power of a classification event from occurring in the power controller chip, the TPS23881 uses the external power FET for classification.
During classification, the voltage on the gate node of the external MOSFET is part of a linear control loop. The control loop applies the appropriate MOSFET drive to maintain a differential voltage between VPWR and DRAIN of 18.5 V. During classification the voltage across the sense resistor in the source of the MOSFET is measured and converted to a class level within the TPS23881. If a load short occurs during classification, the MOSFET gate voltage reduces to a linearly controlled, short-circuit value for the duration of the class event.
Classification results are read through the I2C Detection Event and Channel-n Discovery Registers. The TPS23881 also supports 1, 3, 4, or 5 finger classification for PDs ranging from Class 0 through Class 8, using the Power Enable and Port Power Allocation registers.