MPQ8632-12 voltage ripple issue

DC-DC Power Converters
1

dear managers,

we have to improve voltage ripple ot the MPA8632-12. Could you please guide debugging point below schematic.

Vin : 5.6V
Vout:0.8V
Fsw : 500kHz
Iout : 2A

Volatge ripple : 92mV → simulation result : under 5mV → target : 10mV under

could you please check debugging point on schematic?

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Thank you for advanced!

2

First thing, are you sure you are measuring correctly? The correct way to measure is with a very short ground lead, tied right to the output capacitors. Or a differential probe over the output caps.

If you have a long lead to ground somewhere else, that could be your problem.

3

Hello daejung.kim,

After reviewing the schematic that you’ve posted, the only thing I could find was that VCC should have a 1uF ceramic capacitor should be decoupled to GND. Doing this would add stability to the internal logic of the schematic, which may also contribute to stability of the overall output voltage.

Here is an example schematic that should fit within your application for suggested values for other possible things that may be missing from the MPQ8632-12 datasheet, which should would be a great resource to reference as well:

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Hopefully this helps.

Best,
Krishan

4

Hello Daejung,

I understand you’re facing a similar issue with output ripple in your DC/DC converter. I had a comparable problem and managed to significantly reduce the ripple by making adjustments to the output capacitors. Here’s what worked for me:

  1. Increase the number of ceramic capacitors on the output:
    Ceramic capacitors have low ESR and ESL, making them highly effective for reducing ripple.
    In my case, I added four 100µF ceramic capacitors in parallel, which greatly improved the output
    stability.

  2. Avoid tantalum and electrolytic capacitors:
    These types of capacitors typically have higher ESR and ESL, which can worsen ripple and noise
    issues. Stick to ceramic capacitors for optimal performance.

  3. Results in my case:
    After replacing tantalum capacitors with ceramic ones, the output ripple on my PCB dropped
    from 500mV peak-to-peak to just 68mV peak-to-peak.

  4. Recommended resource from Texas Instruments:
    I also recommend reviewing this document for detailed insights on understanding and reducing
    output noise in DC/DC converters:
    Understanding, Measuring, and Reducing Output Noise in DC/DC Switching Regulator.
    This resource provides excellent guidelines and practical advice that can help you further refine
    your design.
    Let me know if you need any additional details or insights