2 Operation

Once the above connections are made and the appropriate jumpers are set, the EVM is ready to use.

The output voltage of the EVM can be selected by the VSEL jumper to either 3.3 V or 5 V. EN must be cycled when the jumper is changed, in order for the selection to be programmed. Other values of output voltage can be set by removing the VSEL jumper and populating Radj (on bottom) with a 10 kΩ. Values for R_FBT and R_FBB are then selected and populated in the designated locations. See the LM636x5-Q1 3.5-V to 36-V, 1.5-A, and 2.5-A Automotive Step-down Voltage Converter Data Sheet for more information.

The switching mode of the EVM can be changed by using the SYNC/MODE jumper; this selection can be made "on-the-fly".

To use the RESET function, a pullup resistor is required. A place for this resistor is provided on the bottom of the PCB (RPU). Values of 10 kΩ to 100 kΩ are appropriate. Be sure to limit the voltage on this pullup to less than the specified Abs max for this pin.

Some components in the EMI filter are not populated. The user is free to experiment with different EMI filter components as desired.

Loop gain measurements (Bode plots) can be made using the setup shown in Figure 1-4.

The EVM has been designed for maximum flexibility regarding component selection. This allows the user to place preferred components such as the inductor, the capacitors, or both, on the board and test the performance of the regulator. This way the power supply system can be tested before committing the design to production.