Power Filtering: Large Electrolytic vs (MLCC x N)

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cackland
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Power Filtering: Large Electrolytic vs (MLCC x N)

Post by cackland » Fri Nov 20, 2020 9:00 pm

Hey guys,

Quick question regarding power filtering. This isn't specific to modular synths, more so power filtering for power distribution boards for FPV drones. However thought I'd ask the trusty engineers on here.

Generally a 220uF to 1000uf electrolytic capacitor is used for the power filtering on these systems, however wondering in a general sense, could the use of several MLCC low ESR capacitors in series work in the same manner?

What is the benefit to using a large electrolytic over many smaller MLC capacitors?

Thanks

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MikeDB
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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by MikeDB » Sat Nov 21, 2020 7:07 am

Switch mode power supply experts such as Slobodan Cúk tend to now recommend MLCCs exclusively.

Main problem with MLCCs is ensuring the upstream components can take the inrush current as with lots of them in parallel there is a very low ESR. Don't put them after a 7805/12/15.

However solar panels convertors have almost all converted to using MLCCs as they have so much longer a lifetime.
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MikeDB
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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by MikeDB » Sat Nov 21, 2020 7:09 am

duplicate
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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by socom93 » Sat Nov 21, 2020 5:12 pm

cackland wrote:
Fri Nov 20, 2020 9:00 pm
Hey guys,

Quick question regarding power filtering. This isn't specific to modular synths, more so power filtering for power distribution boards for FPV drones. However thought I'd ask the trusty engineers on here.

Generally a 220uF to 1000uf electrolytic capacitor is used for the power filtering on these systems, however wondering in a general sense, could the use of several MLCC low ESR capacitors in series work in the same manner?

What is the benefit to using a large electrolytic over many smaller MLC capacitors?

Thanks
Well an easy answer is space, tantalum and electrolytic both have really higher capacitance density than mlcc.

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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by Grumble » Sat Nov 21, 2020 5:16 pm

cackland wrote:
Fri Nov 20, 2020 9:00 pm
could the use of several MLCC low ESR capacitors in series work in the same manner?
Parallel :sstorm:

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MikeDB
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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by MikeDB » Sat Nov 21, 2020 6:16 pm

socom93 wrote:
Sat Nov 21, 2020 5:12 pm
Well an easy answer is space, tantalum and electrolytic both have really higher capacitance density than mlcc.
Having just laid out several dozen 0402 4.7uF MLCCs I'd tend to say that isn't the case anymore. There were also some 0201s of the same value but they are still a bit expensive (8c vs 1c).
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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by socom93 » Sun Nov 22, 2020 3:58 pm

MikeDB wrote:
Sat Nov 21, 2020 6:16 pm
socom93 wrote:
Sat Nov 21, 2020 5:12 pm
Well an easy answer is space, tantalum and electrolytic both have really higher capacitance density than mlcc.
Having just laid out several dozen 0402 4.7uF MLCCs I'd tend to say that isn't the case anymore. There were also some 0201s of the same value but they are still a bit expensive (8c vs 1c).
Wow 0402 4.7uF ? They must only withstand something like 6 or 10v ?

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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by cackland » Sun Nov 22, 2020 5:39 pm

Yeah the voltage rating is the killer.

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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by cackland » Sun Nov 22, 2020 5:41 pm

MikeDB wrote:
Sat Nov 21, 2020 6:16 pm
socom93 wrote:
Sat Nov 21, 2020 5:12 pm
Well an easy answer is space, tantalum and electrolytic both have really higher capacitance density than mlcc.
Having just laid out several dozen 0402 4.7uF MLCCs I'd tend to say that isn't the case anymore. There were also some 0201s of the same value but they are still a bit expensive (8c vs 1c).
What was the overall capacitance?

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Re: Power Filtering: Large Electrolytic vs (MLCC x N)

Post by MikeDB » Sun Nov 22, 2020 7:32 pm

socom93 wrote:
Sun Nov 22, 2020 3:58 pm
MikeDB wrote:
Sat Nov 21, 2020 6:16 pm
Having just laid out several dozen 0402 4.7uF MLCCs I'd tend to say that isn't the case anymore. There were also some 0201s of the same value but they are still a bit expensive (8c vs 1c).
Wow 0402 4.7uF ? They must only withstand something like 6 or 10v ?
Spot on !!

0201 6.3v
https://lcsc.com/product-detail/Others_ ... 35103.html

0402 10V
https://lcsc.com/product-detail/Multila ... 03694.html
Personally I hate cats ! Charlie the jackdaw on my shoulder also hates cats as his mother was killed by one so I had to raise him until he set off to procreate his lineage.

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