In a standard buck module configuration, the positive output connection (V_OUT) is connected to the internal inductor and the return connection is to the device ground (PGND).

In the IBB configuration, the system ground (SYS_GND) is connected to the V_OUT of the device and the device return path is now the negative output voltage (-V_OUT). Therefore, the buck output is now the system ground, and the buck "ground" becomes the negative output voltage. This shift in topology allows the output voltage to be inverted (with respect to the input voltage).

Figure 1-1 shows the connections for taking the buck regulator and converting it into an IBB.

The connection changes are detailed in the following list:

1. Reassign the buck positive output as system ground.
2. Reassign the buck regulator ground nodes as the negative output voltage node.
3. Positive input remains the same.

Figure 1-1 Converting From Buck to Inverting Buck-Boost Topology