The TPS549A20EVM-737 contains a 10-Ω series resistor in the feedback loop for loop response analysis.

1. Download the Graphical User Interface (GUI) from www.TI.com.
2. Type fusion in the TI search bar.
3. Select FUSION_DIGITAL_POWER_DESIGNER from the search result.
4. Download and install the latest release version of the software. The most current version to date is version 1.8.325 of the Fusion Digital Power Designer.
5. Connect the USB Interface Adaptor EVM (see www.ti.com for more information) to J4 of the EVM. Ensure that Pin 1 of the USB interface adaptor (red wire) is connected correctly to Pin 1 of J4 on the EVM.
6. Connect the USB wire of the USB interface adaptor to one of the USB ports on the computer tower.
7. Ensure that the EVM is powered up and connected to the USB interface adaptor before opening the Fusion Designer GUI.
8. Double click the shortcut icon on the desktop for the Fusion Designer GUI. Use the online version.
9. Double click on the TPS40400, TPS4042x, ect (DEVICE CODE) from the Select Device Scanning Mode window as shown in Figure 7-1.
10. When the GUI is loaded (see Figure 7-2), verify communication between the GUI and the EVM by changing the frequency of the EVM.
    Note:

    The TPS549A20EVM is pre-set to a 400-KHz switching frequency.

11. Use the oscilloscope to monitor the switching frequency on the EVM on TP6.
12. Select a different frequency by clicking on the drop down box of the FREQUENCY_CONFIG:TPS53819 (TPS5391X).
13. Click on Write to Hardware and monitor the change of the switching frequency on the oscilloscope.

See the TPS549A20 datasheet (SLUSAS9) for more information regarding PMBUS registers.

Figure 7-1 Select Device Scanning Mode

Figure 7-2 GUI for the Fusion Digital Power Designer