SDAA401 June   2026 ISOW1050 , ISOW3080 , ISOW6441 , ISOW6442 , ISOW6442-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Enhancing EMC Performance Through Board Design Techniques
    1. 2.1  HF Decoupling Capacitor on Pin 1 and Pin 16
    2. 2.2  Capacitor Bank and Relative Placement
    3. 2.3  Ferrite Bead π-Filter on Supply Rails
    4. 2.4  Isolated Copper Island (KOZ) Under Ferrite Beads
    5. 2.5  Common-Mode Choke on the CAN/RS-485 Cable (ISOW3080 and ISOW1050 Device)
    6. 2.6  Post Island Capacitor
    7. 2.7  Series Resistors or Low-Pass Filter on I/O Traces
    8. 2.8  Y-Capacitor Between GND1 and GND2 (Safety-Critical)
    9. 2.9  Interlayer Capacitor (Substrate Capacitor in the Isolation Region)
    10. 2.10 100µF Bulk Capacitor at VDD Input Rail
  6. 3Summary
  7. 4References

2.1 HF Decoupling Capacitor on Pin 1 and Pin 16

The integrated DC-DC converter switches at ≅60MHz. This frequency (60MHz) along with all harmonic frequencies appear in both radiated and conducted emissions spectrum. A 100nF X7R ceramic capacitor placed directly at VDD (pin 1) and VISO (pin 16) provides a low-impedance shunt path at the fundamental frequency. The capacitor must be placed symmetrically between the supply and ground pin on both sides so that effective inductance from the device supply pin to the capacitance terminal is the same as the device ground pin to the capacitance terminal. (Refer to C27 and C28 placement in the ISOW1050DWEEVM evaluation module).

ISOW6441 ISOW3080 ISOW1050 Schematic Reference From the ISOW1050DWEEVM Evaluation Module for the Mentioned Techniques Figure 2-1 Schematic Reference From the ISOW1050DWEEVM Evaluation Module for the Mentioned Techniques

EMC performance can be further enhanced by using a reverse geometry capacitance (for example 0306YD104KAT2A, see references) or 10nF capacitance (for example GCM155L81E103KA37D, see references) which has much higher series resonant frequency (SRF) and lower equivalent series resistance and equivalent series inductance (ESL/ESR).