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[SOLVED] DC-DC Converter powering MCU

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mayd85

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Hello All,

I am designing a system using a 32-bit MCU operating at 5V. As the peripheral devices operating at 5V are large in number, I am planning to use a 5V, 2A DC-DC converter. The input voltage will be 16 - 36V. I have doubts about powering the MCU from the DC-DC converter, viz.

1. Will the power up overshoot of the DC-DC converter cause any problems to the MCU?
2. How much will the ripple in the DC-DC converter output affect the MCU performance?
3. Are there any other disadvantages of powering the MCU directly from a DC-DC converter?

I have not used a DC-DC converter in any of my designs so far. Hence, the doubts :) .

Thanks.
 

tpetar

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Hi Mayd85 and welcome to EDABoard,

You can power uC with DC/DC converter without problem, you just need to have stable and regulated voltage 5V, if you need 5V, also spikes and high ripple are undesirables and needs additional filtering. uC performance is not linked with ripple, but if you have bad power source spikes, high ripples or unstable voltage, this can cause restarting or damaging uC.
 

mayd85

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Hello Tpetar,

Thanks for the response. The spikes and ripple part is what i am more worried about. I understand that conventional LC filters employed at both input and output of the DC-DC will take care of the ripple and spikes to a great extent. If i have to use additional filtering, what type of filter can i use? Can you direct me to, say, an application note which explains this?
 

tpetar

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  • Input and Output Capacitor Selection.pdf
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  • Power Supply Noise Reduction.pdf
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Ice-Tea

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A properly designed DC/DC converter will have no spikes or ripple of a magnitude that would interact with your MCU. As I assume you did not power your projects out of thin air in the past, this serves as evidence of that. You probably used a trafo based wallwart, a switchmode based wallwart (which operates on a comparable mechanism as DC/DC converters, or a benchtop PSU of some sort which is in the end also based on some sort of switchmode converter (and thus has ripple etc).

If for some reason ripple/noise is too high you can add another LC stage. Operating principle of those is pretty simple: it's a low pass filter, letting DC pass (ie your 5V) and obstructing higher frequencies.
 
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mayd85

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Hello TpeTar & Ice-Tea,

Thanks a lot for your help. It will take me some time to go through the app notes, but the i have got the idea in general. Thanks again. :)
 

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