Overlapping LV Differential Input Specifications (VIHHP  VILLP)

Question: Why does the LV differential input spec (VIHHP, VILLP) overlap?

 

Answer:

The reference inputs and feedback inputs are capable of receiving differential signals. The input specifications VIHHP and VILLP describe the Highest Input HIGH Voltage and Lowest Input LOW Voltage when these input buffers are operating in differential mode. It may be confusing that these two input specs overlap each other. When these inputs are used as differential inputs, the "+" input is HIGH then the "-" input must be LOW, and vice versa. The VIHHP spec describes the possible voltage range of the HIGH input, and the VILLP spec describes the possible voltage range of the LOW input. The reason for the overlap of the specs is that these inputs can accommodate a wide range of differential voltage (400 mV up to V over a wide common mode range (800 mV to VCC . The common mode range is defined as the voltage at which the "+" and "-" input cross.