ESP8266 Community Forum

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?

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.

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).