1 Introduction

Smaller DC/DC bias supplies, such as IIB modules with small component footprint and high-power density are becoming more in demand in numerous applications. IC level transformers with isolation technologies using high frequency power conversion are the main technology drivers enabling smaller IC packages and higher power density. One of the challenges of this trend is EMI. UCC33xxx-Q1 family of devices is part of this trend with ultra-small 4x5x1- $\mathrm{m}{\mathrm{m}}^3$ package and 64MHz switching frequency.

In order to deliver the power from the primary to the secondary side, UCC33xxx-Q1 use a burst frequency in the range of 100kHz-500kHz depending on the load condition. The burst frequency can be explained as low frequency buckets and within these buckets the device switches at a high frequency of 64MHz.

For CE, whose frequency range is 150kHz-30MHz, a pi filter is used to mitigate the burst frequency magnitudes. For RE, whose range is 30MHz-200MHz, the switching frequency and the harmonics are the target and the PCB layout plays a crucial role to keep the target below the limits.