Is a 3-state input and programs the Input Current Limit/Regulation Threshold. A low will program a regulated fast charge current via the ISET resistor and is the maximum allowed input/output current for any ISET2 setting, Float will program a 100-mA Current limit and High will program a 500-mA Current limit. Note that initially the D+/D– detection will latch the charge mode according to the source detected (dedicated charger: ISET; USB Host: at 100 mA) until the ISET2 pin has changed states, indicating the processor or transceiver is controlling the pin.

The detection routine registers the input level (Low–High-Z–High) of the ISET2 pin typically 532 μs after applying input power (V_IN > 3.4 V – UVLO). After the detection routine is complete, which is typically 100 ms after a pullup on the D+ or D– line or after typically 570 ms if no pullup, the IC monitors the ISET2 pin for a change of state. If the state changes (Low–High-Z–High) from the one registered, for more than 5 μs, then the "detected" latched charge mode is released and is then controlled by the ISET2 pin. The completion of the detection routine varies due to the mechanical-plugging action of the USB cable; therefore, it is best to wait ≥ 600 ms after V_IN > 3.4 V to take control of the ISET2 pin.

The following illustration shows two configurations for driving the 3-state ISET2 pin: