In the field of designing printed circuit boards (PCBs), EMC macro-models become increasingly useful to verify EMI performance of PCB with integrated circuits (ICs). This report discussed on estimations of RF currents due to the IC switching by using an IC EMC macro-model, LECCS-I/O, which had been developed to simulate RF power currents of ICs. We focused on not only the RF power current but also the output current of a CMOS I/O gate, since the EMI is caused by RF currents on both power distribution networks and signal lines. We constructed a LECCS-I/O model, with two current sources from measurements and verified the RF currents at power and output pins, comparing to another LECCS-I/O model with a single current source. Results showed that the both models estimate the power current with errors less than 5dB compared to measurements up to 500MHz. Considering the output current, the two-sources model also predicted accurately up to 500MHz, while the single-source model increased errors.