SDAA192 November   2025 UCC33020 , UCC33020-Q1 , UCC33410 , UCC33410-Q1 , UCC33420 , UCC33420-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Setup, EMI Filter and Layout
    1. 2.1 Setup
    2. 2.2 EMI Filter
    3. 2.3 PCB Layout
    4. 2.4 Faraday Shield
    5. 2.5 Schematic
    6. 2.6 Layout
    7. 2.7 EMI Results
    8. 2.8 Bill of Materials: BOM
  6. 3Summary
  7. 4References

2.1 Setup

To avoid coupling of the H filed coming from the integrated transformer of UCC33xx0-Q1 to the LISN, it is recommended to have tightly coupled connections between the positive and the return of the switching loop. The switching loop starts at the 12V battery supply. The switching loop goes through the LISN, and the loop finally connects to the input of the DUT PCB. The following images show an example of tight connections for the whole switching loop for CE and RE.

CISPR 25 CE Setup Figure 2-1 CISPR 25 CE Setup
CISPR 25 RE Setup Figure 2-2 CISPR 25 RE Setup

Comparison between tightly coupled connection and open loop connection; the following images show the difference between tightly coupled and open loop connection for UCC33420-Q1 CE Pout=0.5W.

Tightly Coupled Leads Figure 2-3 Tightly Coupled Leads
CISPR 25 CE Tightly Coupled Leads, Pout=0.5W Figure 2-4 CISPR 25 CE Tightly Coupled Leads, Pout=0.5W
Opened Leads Figure 2-5 Opened Leads
CISPR 25 CE Opened Leads, Pout=0.5W Figure 2-6 CISPR 25 CE Opened Leads, Pout=0.5W