SNVAA61 February 2023 LM5168 , LM5168-Q1 , LM5169 , LM5169-Q1
When using a buck converter as an inverting buck-boost, the connection changes limit the voltage range from input to output that the part can safely operate at. The ground (GND) pin of the IC is no longer referenced to 0 V, and it is now the output of the converter. As a result, the maximum voltage over the IC can be calculated as VIN minus -VOUT. For example, if the input voltage is 60 V and the output is -80 V, then the voltage over the IC is 140 V. In the case of the LM5168, this configuration would exceed the maximum input voltage of 115 V across the part listed in the data sheet. It is important to keep the input and output voltage difference within the maximum voltage rating of the IC.