A display device includes a display panel, a display panel driving circuit, and a power management integrated circuit that generates driving voltages, receives driving set data from a timing controller, stores driving hex values corresponding to the driving set data in first internal registers, and determines voltage levels of the driving voltages based on the driving hex values. The power management integrated circuit divides the driving hex values into upper and lower decimal values, derives a result decimal value by applying the upper and lower decimal values to a first authentication-formula, generates a result hex value based on the result decimal value, compares an authentication hex value corresponding to authentication data received from the timing controller with the result hex value, and selectively operates in a normal mode or in a protection mode based on a comparison result between the authentication hex value and the result hex value.