Using TP3, TP6 and TP9 oscilloscope probe PCB test points: The UCC14141-Q1 is a high frequency DC-DC module that requires careful measurement for accurately capturing transient events and measuring high frequency, AC ripple voltage. Remove the “witch hat” probe tip cover and ground lead from the scope probe. If scope probe ground springs are not available, wrap a piece of 22 AWG bare wire around the scope probe ground ring or use a fitted ground spring and insert the probe tip and ground into the EVM as shown in Figure 4-2.

Figure 4-2 UCC14141EVM-068, PCB Scope Probe Test Points

The EVM output nomenclature (VDD, VEE, COM) corresponds to what is commonly used when referring to isolated gate driver ICs. As shown in Figure 3-1, TP4 (COM) is the midpoint of a capacitive divider and is intended to connect to the COM pin of the isolated gate driver IC. When the UCC14141-Q1 is used to bias a gate driver IC, VDD (VDD-COM) and VEE (VEE-COM) are referred to with respect to COM. Therefore, COM is not considered as a virtual GND to the gate driver IC. Since the midpoint of the capacitive divider is sensitive to charge imbalance, for the purpose of probing the EVM, do not connect any ground-referenced, test equipment to TP4 (COM). A battery powered DVM can be used to measure VEE with respect to COM. When testing the EVM as a stand-alone bias power supply, oscilloscope probing of the secondary-side outputs is limited to TP3 and TP6 which are referenced to VEE. This means VDD shows an oscilloscope measurement of VDD+|VEE| and VEE shows |VEE|. Connecting any ground-referenced test equipment to COM can result in a false but safe overcurrent condition causing VDD and VEE to inadvertently drop out of regulation during light load operation.