Phase compensation in an I/O (input/output) circuit includes variable, programmable slope. A phase compensation circuit can apply phase compensation of one slope and dynamically change the slope of the phase compensation to allow for better tracking of environmental conditions. The phase compensation circuit can generate a linear code to apply phase compensation to lock phase of an I/O signal to a phase of a timing signal. The circuit selectively adjusts the linear code with a variable, programmable slope, where the slope defines how much phase compensation is applied per unit change in the linear code. The circuit applies the adjusted linear code to a lock loop to lock the phase of the I/O signal to the phase of the timing signal.