Decoding EMI suppression: Next-generation circuit technology revealed

This article provides a comprehensive introduction to practical application methods and strategies for suppressing electromagnetic interference (EMI) in DC/DC converters using integrated power MOSFETs and controllers. The key technologies in converter design are discussed, including PCB layout, packaging design and input filtering, etc., aiming to provide a systematic solution to enhance the EMI performance of the equipment.


Basic knowledge of electromagnetic interference

Electromagnetic interference (EMI) is a common problem in electronic equipment, especially in DC/DC converters using fast switching technology. High dv/dt and di/dt switching events in converters can produce broadband harmonics and ringing, and these disturbances can affect surrounding electronic equipment through near-field coupling. For example, body diode reverse recovery can cause significant ringing, affecting power lines and output buses such as USB lines.

EMI considerations in converter design

PCB layout

PCB layout is an important aspect of controlling EMI. Reasonable layout can effectively reduce EMI radiation and conduction. The layout should minimize the power loop area to reduce parasitic inductance and the spread of electromagnetic fields. The bootstrap capacitance and switching node of the high-side MOSFET should use the smallest possible loop area, taking into account the trade-off between switching power losses and EMI.


Package and pin design

Using optimized packaging and pin layout can significantly improve EMI performance. For example, the HotRod package optimizes switch node ringing and switching losses by reducing the parasitic inductance of the package. Proper pin layout can also reduce the area of the current loop, thereby reducing EMI.

input filter

The design of the input filter is also critical, and the attenuation of DM and CM noise can be optimized through hierarchical design. Using DM inductors and CM chokes with lower self-resonant frequencies can effectively filter out high-frequency and low-frequency interference.

Specific strategies for EMI

- Shielding and via stitching: Through metal shell shielding and via stitching technology, the coupling of radiated noise can be further reduced.
- Optimize the location of inductors and capacitors: Place inductors and capacitors as close to critical pins as possible to reduce the impact of EMI.
- Comprehensive layout considerations: During design, all high-frequency current paths should be comprehensively considered to avoid passing through sensitive components.

Through the above comprehensive measures, the EMI generated in the DC/DC converter can be effectively suppressed and the stability and performance of electronic equipment can be improved.