How to Handle TPS61089RNRR with Excessive Ripple and Noise

How to Handle TPS61089RNRR with Excessive Ripple and Noise

When dealing with excessive ripple and noise issues in the TPS61089RNRR , a boost converter from Texas Instruments, it's essential to understand the root causes and how to systematically address them. Let's break down the possible reasons behind the problem and how to resolve it step by step.

Understanding the Issue

The TPS61089RNRR is a high-efficiency boost converter used for Power ing various devices with a stable output voltage. However, ripple and noise can negatively affect its performance, especially in sensitive applications like audio or communication systems.

Ripple refers to unwanted fluctuations in the output voltage, typically caused by switching frequency or power supply fluctuations. Noise can be defined as any unwanted signal that interferes with the desired output, often originating from switching transients or external sources.

Possible Causes of Excessive Ripple and Noise Inadequate capacitor Selection The ripple and noise can result from improper selection of input or output Capacitors . Capacitors with poor quality, wrong type, or incorrect value can cause instability. Insufficient Grounding and Layout Issues Poor PCB layout, improper grounding, and inadequate routing of traces can introduce noise. Long traces, improper grounding, or a lack of decoupling can exacerbate ripple problems. High Switching Frequency The TPS61089RNRR operates at a switching frequency of 2.5 MHz. If the layout is not designed properly, these high frequencies can cause significant noise and ripple. External Interference Electromagnetic interference ( EMI ) from other components or nearby power sources can contribute to the ripple and noise. Poor Filter Design The output filter might not be optimized, or missing altogether, leading to higher ripple levels. Filters help smooth out the voltage, reducing ripple. Step-by-Step Solutions

Now that we know the potential causes, let’s dive into the solutions to reduce or eliminate ripple and noise:

1. Check Capacitor Selection

Input Capacitors: Ensure you're using a low ESR (Equivalent Series Resistance ) ceramic capacitor for the input side. A typical value would be 10 µF or higher for stable operation.

Output Capacitors: Use high-quality, low ESR capacitors. A combination of ceramic and tantalum capacitors (e.g., 22 µF ceramic and 10 µF tantalum) is ideal for reducing ripple.

Ensure that the capacitors meet the recommended specifications outlined in the TPS61089RNRR datasheet for optimal performance.

2. Improve Grounding and PCB Layout

Minimize Trace Lengths: Keep high-current traces as short and thick as possible to reduce resistance and noise. Separate Power and Signal Grounds: Create a solid ground plane to minimize the interference between power and signal circuits. Decoupling: Place decoupling capacitors close to the IC pins to filter out high-frequency noise. This will help reduce the switching ripple. Inductor Placement: Position the inductor as close to the IC as possible to minimize high-frequency noise coupling.

3. Use an Appropriate Filter

If not already in place, design a proper output filter. This can be done using a low-pass filter to smooth out the ripple. Typically, a small inductor combined with a low ESR capacitor will do the trick. You can also add ferrite beads to the input or output to further reduce high-frequency noise.

4. Shielding and EMI Protection

Physical Shielding: Add metal shielding around the boost converter to reduce electromagnetic interference (EMI) from external sources. Ferrite Beads and Snubber Circuits: Use ferrite beads at the input or output to reduce high-frequency noise, or a snubber circuit across the switch for better noise suppression.

5. Adjust the Switching Frequency (if possible)

If the noise persists due to the high switching frequency, try adjusting the frequency slightly. Some designs may allow fine-tuning of the switching frequency, which can help reduce noise. However, always ensure that this doesn’t interfere with the efficiency or stability of the boost converter.

6. Use a Power Supply Filter

For particularly sensitive applications, add a dedicated power supply filter at the output. A bulk capacitor can help stabilize the voltage and reduce noise, especially in systems where even small fluctuations are problematic.

7. Test and Verify

After implementing these changes, perform rigorous testing with an oscilloscope to verify the reduction in ripple and noise levels. A clean, stable DC output with minimal ripple should be the goal. Final Thoughts

Excessive ripple and noise in the TPS61089RNRR are often caused by poor capacitor selection, improper layout, or insufficient filtering. By following these steps, you can systematically address the issue, ensuring a more stable, noise-free power supply for your application. Remember, each system is unique, so it may take some fine-tuning to achieve the desired results.

If you follow the suggestions closely and validate your changes, you should see significant improvements in the performance of the boost converter.