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Voltage regulation ESP-WROOM-02D/U (or any MCU?)

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oliv3r:
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?

A small schematic added to show what I mean (hopefully :p).

kripton2035:
P = U x I = (12-3.3) x 0.5 = 4.35W
really too much for the small 1117
you must input 5v at the 3.3v regulator...

oliv3r:
Thanks kripton for your response, but my question had absolutly nothing to do with that 1117 :D

But in that light, according to the datasheet, it's a 3V3 LDO with a 1A output current. Input voltage is upto 20V. I was under the impression that it could deliver the 1A when feeding it 20V. There's also no graph in the datasheet that would indicate this (input v vs current capability. So what makes you say this? https://eu.mouser.com/datasheet/2/115/AZ1117-1596017.pdf

Just a reminder to all responders, I'm wondering how to create a pull-up voltage for the MISO without adding a 5V LDO, but instead use a 5v1 zener.

DavidAlfa:
Nope.
It means "It will not explode up to 20V, and might will provide up to 1A output", doesn't mean it can provide all that at the same time.
Use a buck regulator, not that electric stove. LDO can be ok for small voltage drops, ex. from 5 to 3.3V, not from 12 to 3!

Anyways, read the datasheet of the device you're connecting to, and check the ViH level for digital pins.
Sometimes it's % of VDD, otyhers it's an absolute threshold.
For example, for the ESP8266 it's 0.75*VIO, meaning it will read "1" starting from (0.75*3.3)=2.475V.

When devices talk different voltage levels, what you should search is "voltage level translation" or "voltage level shifter".

oliv3r:

--- Quote from: DavidAlfa on November 12, 2022, 02:53:24 pm ---Nope.
It means "It will not explode up to 20V, and might will provide up to 1A output", doesn't mean it can provide all that at the same time.
Use a buck regulator, not that electric stove. LDO can be ok for small voltage drops, ex. from 5 to 3.3V, not from 12 to 3!

--- End quote ---

So how does one search for a proper part? buck/ldo doesn't matter much to me, in this quick sketch I did in the schematic, I just picked a sensible part, but it's not so sensibe! But how is one to know this based on the specs?

Regardless, thanks for the tip, and for the real thing I'll def. look for a buck ;)


--- Quote from: DavidAlfa on November 12, 2022, 02:53:24 pm ---Anyways, read the datasheet of the device you're connecting to, and check the ViH level for digital pins.
Sometimes it's % of VDD, otyhers it's an absolute threshold.
For example, for the ESP8266 it's 0.75*VIO, meaning it will read "1" starting from (0.75*3.3)=2.475V.

--- End quote ---
There is no datasheet :( So we dont' know. We only know that the other side supplies 12V and talks 5V. The ESP is known to have 5V capable IO's (this is well documented by now), but the output (MISO) is 3v3, so we need to pull it up to 5-ish volts. Its been known to cause problems. Alternative boards use a 5V ldo, but I'd rather avoid that if possible.


--- Quote from: DavidAlfa on November 12, 2022, 02:53:24 pm ---When devices talk different voltage levels, what you should search is "voltage level translation" or "voltage level shifter".

--- End quote ---
Ah, the whole point of this design, is to avoid the level shifter :)

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