The CY23EP05 cannot deliver a slew rate of 1.5V/ns at the 30pF load. The spec for rise/fall time @ 30 pF load and 3.3V operation with high drive (-1H) setting has a maximum of 1.2ns. Since the rise/fall time is measured from 0.8V to 2.0V, this gives a minimum slew rate of 1.2V/1.2ns = 1V/ns. The CY23EP05 has the fastest edge rate among our buffers-- the CY2305C only supports 1.2V/1.5ns = 0.8V/ns minimum edge rate. The only way to get a 1.5V/ns or faster edge rate from any of our devices is to significantly decrease the load to around 15pF.