ESP32 Forum

I am designing a PCB using the ESP32-D0WDQ6, which will be running the Wi-Fi pretty much full-time. I'm trying to decide on the bulk capacitor for the chip, would it be preferable to use a:

100uf 1210 XR5 10V MLCC: https://www.digikey.com/product-detail/ ... ND/3891450

or…

220uf 1411 6.3V tantalum polymer: https://www.digikey.com/product-detail/ ... ND/2231003

My concern is the ESR on the tantalum, low for a tantalum at 35mOhms but I'm wondering if the much lower ESR ceramic will handle the Wi-Fi currents spikes more effectively, or if the extra 120uf from the tantalum would be more effective towards handling the spikes. Also wondering if more than 100uf is needed or useful for the ESP32. The ceramic costs about $0.10 more from the board house I will be using but I’m not concerned about the price. I don't expect my usage to ever exceed the 2000 hour rating on the tantalum although it is possible it could, so that weighs a bit on my decision also. Operating temperature won't be an issue, the board will be in a housing at room temperature which will also have a few other ICs and components, but nothing which will create a lot of heat. My main concern is how the performance characteristics of the two capacitors relate specifically to the needs of the ESP32, and which one would be superior. Any insights would be much appreciated.

To be clear, this would be replacing the 10uf C13 capacitor in the datasheet section 2.1, and will be placed as close to the chip as possible behind the other components. https://www.espressif.com/sites/default ... es_en.pdf

My intuition tells me that it probably matters much. Good call on using an 10V ceramic, though, as ceramics loose a lot of capacity when used close to their voltage rating. If you're worried about the ESR of the tantalum, I'd just add a small (1uF) ceramic next to it; WiFi power use tends to be mostly spikey and the 1uF can soak up those spikes.

ESP_Sprite wrote: ↑

Mon Aug 24, 2020 8:06 am

My intuition tells me that it probably matters much. Good call on using an 10V ceramic, though, as ceramics loose a lot of capacity when used close to their voltage rating. If you're worried about the ESR of the tantalum, I'd just add a small (1uF) ceramic next to it; WiFi power use tends to be mostly spikey and the 1uF can soak up those spikes.

Thank you for that, much appreciated. I was wondering if you thought the 220uf tantalum with the 1uf ceramic would be more preferred than the 100uf ceramic alone? If it was your board what would you use? Or what about a 220uf tantalum with a 10uf ceramic, along with the 100nf? I see there's 2x 10uf caps and a 1uf used in the data sheet, is that 1uf necessary to filter a certain range of frequency? I guess part of what I'm wondering is if the 220uf is overkill at all or if it will lend some benefit when paired with another small ceramic bulk cap. I've seen mentioned on this site by moderators that the 100uf is definitely preferred over a 10uf or a pair of them, and now am wondering if more would be better.