Resistors R1, R2, R3, and R4 are all 0 Ω resistor components. The input terminals (IN+ and IN-) have corresponding sense lines so that the inputs to the device can be terminated on the lines with 50 Ω to an oscilloscope. This allows the input signals to be observed with minimal loading and distortion. All input connections are through SMA connectors. If the input signal to the device does not need to be evaluated on an oscilloscope, R3 and R4 can be left uninstalled. However, your input signal may need to be terminated if the oscilloscope's 50 Ω setting is not connected.

The TLV3601EVM has an optional resistor pad on the input (R5) side of the device meant for termination of the input signal. R5 can be populated with a 100 Ω resistor if applying an unterminated LVDS signal to the board. Alternatively, it can be populated with a 50 Ω resistor if applying a function generator output that needs a 50 Ω termination. One of the inputs would be GND and the board would be operating in split supply in this situation. Otherwise the pad can be left unpopulated.

Figure 6-3 Input Side Schematic