The Vcm input (J3) is optional and sets the common mode of the output pins. The LMH5485-SP will automatically self-bias the output common-mode voltage to the mid-supply voltage if the Vocm pin is not connected. This is the optimal voltage for maximum output swing and best linearity.

The valid range of the Vocm is 0.94-V above the negative supply to 1.2-V below the positive supply. For example, on a ±2.5-V split supply, the Vocm pin can be set anywhere from −1.56-V to 1.3-V. With a single 5-V supply the valid range would be 0.94-V to 3.8-V. Remember, the outputs of the LMH5485-SP can swing from rail to rail; the maximum output swing available, however, is reduced when the Vocm pin is set to a voltage other than mid-supply.

If providing 50-Ω termination for the Vcm input signal source is desired, C6 can be populated with a 0-Ω resistor and R5 populated with a 50-Ω resistor.