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I have been researching the ESP 12, and I am ready to hook it up. Because the Wi-Fi uses high current, it has been advised to add a stabilizing capacitor across the Vcc and ground terminals of the ESP 12. These are on opposite sides of the ESP 12.

I am wondering whether the capacitor should be right beside the Vcc, or right beside the ground.

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Ideally, a decoupling capacitor should be as close as you can get it to both the supply terminals of the device. However, when the supply terminals are far away, you must compromise. The underlying goal should be to minimize impedance in the local power supply, which means minimizing trace inductance.

The best solution would probably be a solid ground pour, and then placing the decoupling capacitor near Vcc and tying it to ground with big via or a few small vias.

If you do not have the stackup to do a ground pour, then place the capacitor near Vcc or ground, and connect the capacitor to the far terminal with a relatively wide trace.

Keep in mind, the ESP12 has its own local small value decoupling for handling high-frequency power requirements; the decoupling that you are placing should be designed to supply larger transient supply spikes (for instance, when the radio kicks in). As a result, the frequencies that this decoupling cap must handle are lower, and therefore the impedance requirements are somewhat relaxed (meaning a short length of trace in between cap and module isn't such a huge issue). I have done a design incorporating an ESP12 module, and I used a single 47 uF ceramic cap, placed near the VCC pin of the module. Depending on the nature of your power supply, you may want to use more decoupling, perhaps several 47 uF ceramics in parallel.

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  • \$\begingroup\$ I am just using a perfboard. So, would it be best to put the cap hear Vcc, and use a thick solid wire to ground? And thank you for the suggestions of appropriate capacitance. \$\endgroup\$ – Fed Mar 18 '17 at 17:33
  • \$\begingroup\$ Yes, with perfboard, it's probably best to use a large electrolytic and maybe a small electrolytic or big ceramic (with lowish ESR) in parallel, and as long as you have reasonable gauge wire, it'll be fine. \$\endgroup\$ – uint128_t Mar 19 '17 at 0:58
  • \$\begingroup\$ So would you say a 10uF and a 220uF in parallel, both near Vcc, sharing a 20 gauge solid wire to the ESP12's ground? If not, could you suggest a combination? \$\endgroup\$ – Fed Mar 19 '17 at 1:31
  • \$\begingroup\$ Yeah, that's probably sufficient \$\endgroup\$ – uint128_t Mar 19 '17 at 1:33

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