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I have been recently interested into creating my own CC2530 board for a Zigbee device and was following the sample schematics provided by TI. I am a newbie to board design and have some basic questions, here is my first one.

I understand that decoupling capacitors are needed with a power source to smooth voltage when it drops for different reasons during operation. The cc2530 has multiple pins connected to the power source.

Why does the sample circuit attach a capacitor for every pin? Wouldn't this be equivalent to one capacitor between power source and the ground, or do we need to make sure while designing the PCB to locate each capacitor as near as possible to the pin that it is smoothing?

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Yes, especially with RF devices. You want to follow the actual capacitance and package recommendations for these parts. You do need that 10u, 0.1u and 220pF values, even though they might seem redundant.

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  • \$\begingroup\$ Thanks for your answer, so the second part of my question: Do I need to ensure that each capacitor is located as near as possible to the corresponding pin in the PCB design? \$\endgroup\$
    – Bishoy
    Commented Mar 26, 2022 at 16:26
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    \$\begingroup\$ yes. As Lior says, follow the guidance TI gives you. There's a data sheet, there's high-speed layout application notes. Also, stay as close as possible to the design of existing demo/ evaluation boards. Typically, IC vendors put the design files online so you can replicate the design. RF design is not always trivial, and starting off a design that already works is much better than designing from scratch – especially, no offense, since you seem to be still building up basic experience and understanding, judging by these questions! \$\endgroup\$
    – Marcus Müller
    Commented Mar 26, 2022 at 16:32
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    \$\begingroup\$ Sure I am not intending to ignore the recommendations specially as I am a beginner :) But this is the one thing not mentioned (or at least I didn't find yet) in the datasheet/samples, which is if we should move the capacitors near to the pins. My guess is they are relying on the fact that people knows by experience and that is why I am asking experienced people here. Thanks. \$\endgroup\$
    – Bishoy
    Commented Mar 26, 2022 at 16:39
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    \$\begingroup\$ @Bishoy Use the reference design board layout (link) as a starting point, not just the schematics. Stay as close to this board layout as possible. \$\endgroup\$
    – TypeIA
    Commented Mar 26, 2022 at 17:00
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    \$\begingroup\$ @Bishoy - think about the time taken to deposit or dump energy into/from a capacitor. It's RC. If the resistance is higher, so is the time. If the capacitor is closer to the ic pins, the resistance of the wire between them is lower. \$\endgroup\$
    – enhzflep
    Commented Mar 27, 2022 at 4:43

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