A 2 x VDD I/O buffer based on deterministic PVT variation detection algorithms to achieve slew rate compensation is proposed in this brief. By using the P-PVT and N-PVT Variation Detectors consisting of an inverter and a capacitor, the slew rate variation is significantly reduced against the PVT variation. Besides, the source-drain leakage current is reduced by turning off the auxiliary current paths after the charging and discharging transients are completed. The proposed design is implemented using a typical 40-nm CMOS process. The area of the I/O buffer is 0.216 x 0.052 mm(2). Based on post-layout simulations, the slew rate variation is reduced 38.29% after the process, voltage, temperature, and leakage compensation in the worst case.