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Usage of polarised capacitor in parallel with non-paralised capacitor

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Hi there,
I am studying the user manual of an evaluation board for a charging circuit. Link to the manual is below.
One design consideration caught my eye. I would like to know what the purpose of polarised 2.2uF capacitor (C204) is when there is already a 4.7uF capacitor (C203).
Many thanks in advance!


Compare the ESRs, and model the equivalent parallel impedance. :-+

Also, it's not obvious where they've placed all those capacitors, but it's generally a bad idea to put multiple different values in parallel right beside each other.  If they're spread around doing local bypass, that may be okay, but that might not be necessarily either.


In grad school, we had undergraduate students as cheap, yet clever, technicians.
I once hand drew a circuit (for a onesie) with analog and CMOS devices on the same Vectorboard, with +15 V and -15 V supplies.
To make the drawing less messy, I put a rectangle for each IC into the lower left-hand corner of the drawing, showing the power and ground connections, with appropriate bypass capacitors on each socket.
Actually, IIRC the drawing was explicit, showing the capacitor directly at the pins and wires from there to the power lines and ground symbol.
Invoking circuit theory, the tech substituted a single 1 uF capacitor for 10 0.1 uF capacitors.
With modern drafting, the careful location of the bypass capacitors is done at the PCB layout stage, moving the parts from a rats' nest to the neighborhoods of the devices.

David Hess:
The parts list says C204 is 2.2uF ceramic, so the schematic symbol is wrong.


--- Quote from: insanoff on November 27, 2022, 06:17:13 pm ---I am studying the user manual of an evaluation board for a charging circuit. Link to the manual is below.
--- End quote ---
Are they all populated? Evaluation boards often have extra footprints so the customers can try different solutions.


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