The UCC33421-Q1 integrated isolated power solution simplifies system design and reduces board area usage. Proper PCB layout is important in order to achieve optimum performance. Here is a list of recommendations:

• Place decoupling capacitors as close as possible to the device pins. For the input supply, place 0402 and 0805 ceramic capacitor between pins 2 and 3 (VINP) and pins 4, 5, 6, 7 and 8 (GNDP). For the isolated output supply, place 0402 and 0805 ceramaic capacitora between pins 10 and 11 (VCC) and pins 12, 13, 14, 15 and 16 (GNDS). This location is of particular importance to the input decoupling capacitor, because this capacitor supplies the transient current associated with the fast switching waveforms of the power drive circuits.
• Because the device does not have a thermal pad for heat-sinking, the device dissipates heat through the respective GND pins. Ensure that enough copper (preferably a connection to the ground plane) is present on all GNDP and GNDS pins for best heat-sinking. Placing vias close to the device pins and away from the high frequency path between the ceramic capacitors and the device pins is essential for better thermal performance.
• If space and layer count allow, it is also recommended to connect the VINP, GNDP, VCC and GNDS pins to internal ground or power planes through multiple vias of adequate size. Alternatively, make traces for these nets as wide as possible to minimize losses.
• Pay close attention to the spacing between primary ground plane (GNDP) and secondary ground plane (GNDS) on the PCB outer layers. The effective creepage and or clearance of the system reduces if the two ground planes have a lower spacing than that of the device package.
• To ensure isolation performance between the primary and secondary side, avoid placing any PCB traces or copper below the UCC33421-Q1 device on the outer copper layers.