SLYT823 March   2022 LM25149-Q1


  1. 1Introduction
  2. 2AEF compensation
  3. 3AEF damping
  4. 4AEF performance with both compensation and damping
  5. 5Conclusion
  6. 6References
  7. 7Related Websites


As an excellent alternative to traditional bulky and expensive passive filters, active electromagnetic interference filters (AEFs) can help designers deal with ever-increasing EMI challenges, improve power density, and reduce the cost of power solutions. References [1] and [2] demonstrate an approximate 50% size reduction and >75% volume reduction with an AEF implemented in the Texas Instruments LM25149-Q1 buck controller.

Most AEFs use operational amplifier (op amp)-based active circuits to sense noise and inject an appropriate cancellation signal to reduce EMI, such as the AEF integrated into the LM25149-Q1. To achieve the best performance with this kind of AEF, the op-amp circuits need to be stable and the op amp should not saturate. Otherwise, the AEF would have worse performance and may even inject additional noise into the system [3]. This article discusses the proper compensation and damping techniques to achieve stability and the best performance of an AEF.