How to Address Noise and EMI Issues in TPS54328DDAR Power Supplies

How to Address Noise and EMI Issues in TPS54328DDAR Power Supplies

1. Introduction

The TPS54328DDAR is a highly efficient and widely used DC-DC buck converter. While it provides excellent performance in terms of power efficiency, users may encounter issues related to noise and electromagnetic interference (EMI). These issues can negatively affect the power supply’s performance and may also cause malfunctions in nearby sensitive electronic devices. In this guide, we will explore the root causes of these problems and how to address them effectively.

2. Understanding the Problem: Noise and EMI

Noise and EMI are unwanted electrical signals that interfere with the normal operation of circuits. In the case of the TPS54328DDAR, this can manifest as:

Electromagnetic interference (EMI): High-frequency noise generated by the switching of the power supply. Conducted noise: This type of noise travels along power lines or other wiring, affecting other components. Radiated noise: EMI that spreads through the air, potentially affecting other nearby electronic devices. 3. Possible Causes of Noise and EMI

Several factors can contribute to noise and EMI issues in power supplies. Some common causes include:

Inadequate Filtering: Insufficient or poorly placed filters can allow high-frequency noise to propagate. Improper PCB Layout: A poor PCB design can create unintentional antenna s or paths that amplify noise and EMI. High Switching Frequencies: The TPS54328 operates at relatively high switching frequencies, which can cause noise if not properly managed. Grounding Issues: Poor grounding techniques can cause noise to loop through the system, making it more difficult to eliminate. Lack of Shielding: Inadequate shielding around the power supply and sensitive circuits can allow EMI to leak. 4. How to Solve Noise and EMI Issues

To resolve noise and EMI issues in TPS54328DDAR power supplies, follow these step-by-step solutions:

4.1 Step 1: Improve Input and Output Filtering Add more input capacitor s: Use ceramic capacitors (e.g., 10µF and 0.1µF) at the input to reduce high-frequency noise. Enhance output filtering: Use additional LC filters (inductor and capacitor) to reduce noise at the output. Adding a small ceramic capacitor (0.1µF to 1µF) between the output and ground can help. Use a low ESR (Equivalent Series Resistance ) capacitor at the output to better filter high-frequency noise. 4.2 Step 2: Improve PCB Layout Minimize the loop area: Ensure that the power and ground paths are as short and wide as possible to reduce inductance and resistance. Separate power and signal grounds: Use a star grounding technique, where all grounds connect at a single point, preventing noise from traveling into sensitive areas. Route high-frequency switching paths carefully: Minimize the length of high-current paths and avoid running these traces parallel to signal traces, as this can introduce noise. 4.3 Step 3: Shielding and Enclosures Use shielding: Enclose the power supply in a metal shield to contain radiated EMI. The shield should be grounded to prevent it from becoming a source of interference. Close the shield: Ensure the shield is securely grounded at the power supply’s input and output to prevent EMI from escaping. 4.4 Step 4: Proper Grounding Techniques Ensure solid ground connections: Use low-inductance ground planes and connect all grounds at a single point to minimize noise coupling. Connect all capacitors and other filtering components directly to the ground plane to prevent noise from returning to sensitive areas. 4.5 Step 5: Adjust Switching Frequency (if applicable) Lower switching frequency: If possible, use external circuitry or adjust the settings to reduce the switching frequency, as higher frequencies tend to generate more EMI. Use a frequency modulation technique: Some designs include a modulation feature to spread the switching frequency, which can help in reducing EMI. 4.6 Step 6: Use EMI Mitigation Components Add ferrite beads : Ferrite beads can be added to the input and output lines to filter high-frequency noise. Use common-mode chokes: These help to filter out noise from both the power lines and the ground line, minimizing conducted EMI. Install snubber circuits: A snubber circuit placed across the switch can reduce high-frequency ringing during transitions. 5. Testing and Validation

After implementing these solutions, test the power supply under operational conditions:

Use an oscilloscope to measure noise levels at the input and output. Check EMI levels using an EMI receiver and ensure the system complies with relevant standards (e.g., CISPR 22, EN 55022). Perform thermal checks to ensure that the modifications have not affected the power supply’s thermal performance. 6. Conclusion

Addressing noise and EMI issues in TPS54328DDAR power supplies involves a combination of proper filtering, PCB design, grounding techniques, and shielding. By carefully considering these aspects and following the outlined steps, you can minimize noise and ensure stable, interference-free operation of the power supply, leading to better overall system performance.