Electronics > Beginners
BOM prob. ESR Output Capacitor - TPS5560200
Docara:
Hi
I'm following primarily TIs workbench software for a 13.2V(nom) to 3.8V converter. The output is going into a LDO (200mA DO) Linear for the final 3.3V. (thanks Dave for your 1cent reg series check out AP2127K-3.3) ;D
The Schematic states a 47uF 2.0mOhm ESR output multiple layer ceramic capacitor is required, I will be needing 30-40 of the little f**kers and I'm getting hit for between £0.41 and £1.00 EACH even on LCSC!! Even if I bang in a couple of lower values I'm getting stung
Do I really need an ESR here, if yes what is the importance of ESR in this location, why such a low value and what alternatives could I use - I don't really know when to use different types of caps in situations like these (Dave if your watchin' mate hint hint :-+)
Lastly, for completeness, on the data sheet of the AP212 the input and output caps are a 1uF.
Thanks
thinkfat:
How about just putting two or three of these:
https://lcsc.com/product-detail/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT_SAMSUNG_CL10A226MQ8NRNC_22uF-226-20-6-3V_C59461.html
If you're really concerned about ESR. Normally, ESR for a MLCC capacitor is a minor issue. For very high switching frequencies, ESL is maybe more important.
Docara:
Hi thinkfat,
In answer to your question, it is because I do not know enough about the implications or reasons for using an ESR Cap in a given situation.
Hence why I was asking why you need an ESR cap here.
I prefer to put caps in with a higher voltage head room than 2V ish, so I have been looking at the 10-25V ranges
thinkfat:
Not sure what you think an "ESR Cap" is. ESR -> Effective Series Resistance, it's a parameter of every capacitor, so the design asks for a 47µF capacitor with very low ESR.
You can use any MLCC capacitor for that, usually their ESR is in the single-digit milli-Ohm range. If you think the ESR is not low enough, just put a couple of them in parallel.
10V will be fine, I'm sure you'll find something on LCSC for little money.
They get expensive at higher capacities and smaller footprint size, but 22µF is available in 0805 size for less than 10 cents, just put three of them.
Docara:
I don't know what ESR is or how it impacts a circuit that's why I have posted a question here
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