ESP8266 Community Forum

- Sat Oct 22, 2022 6:52 am #95419 Hey guys,

I'm trying to do a design based on a WROOM-02 (replacement of a wemos d1, so stuck with that one) and need to do voltage regulation. Obviously the WROOM-02 needs 3v3@500mA (right? can't do with much less then that?) so finding a (V)LDO for that isn't a big issue. However, the power input is 12V and the SPI bus that we need to talk to is 5V, which means 5V pull-up MISO (the wroom is a slave). However, there is no 5V available for this, thus either a dual output LDO is needed (hard to source with the needed specs) or some other means are needed.

I could daisy chain regulators (better for efficiency of the 3v3 part? But that means needing a bigger 500mA 5V regualtor, just to regulate the 3v3 later. What alternatives are there? I could do a 5V zener for the pull-up, but how are we looking on consumption? We'd be talking super low power usage, just that of the pull-up ... and what value would be best for that?

- Sun Oct 23, 2022 5:21 am #95425 You can get an idea about voltage regulation from this design:https://www.pcbway.com/project/shareproject/Development_Board_ESP_WROOM_32U.html
This is an ESP WROOM 32U development board. If this design does not help, you can ask your question in the same website.

- Mon Oct 24, 2022 4:31 am #95432 Not sure how your link is relevant at all. They use a USB carrier giving them VUSB freely available.

Since a picture is worth more then words, here's what I'm talking about.

Right now however, I'd be using 2 resistors, R1 is the current limiter for the zener, So 5V (probably 4.7 or 5.1) will make the max current available to the pull-up R4. R4 would them limit this even more so. I'm not even sure I'd need R4 at all however, schematic wise it looks better (pull-up resistor R4 and current limiting resistor R1).

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