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

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Not sure if I missed that:
The ESP-WROOM-02 datasheet says 500 mA max, but 80 mA average. 
Most likely the ESP will use a few hundred mA just for wifi transmit, which are short pulses. So an LDO would only see 0.7 W on average.


--- Quote from: Martinn on December 06, 2022, 07:23:40 pm ---Not sure if I missed that:
The ESP-WROOM-02 datasheet says 500 mA max, but 80 mA average.
Most likely the ESP will use a few hundred mA just for wifi transmit, which are short pulses. So an LDO would only see 0.7 W on average.

--- End quote ---
This is OK for thermal design, since wifi transmit peaks are in order of tens of milliseconds, and thermal inertia of even small SMD regulators is larger. You still need to be sure you don't exceed the maximum current of the regulator because they employ short circuit current limiting and that may get triggered not much beyond the maximum current. (Operating beyond maximum ratings is not guaranteed, no matter how short it is. Voltage may also drop more than one expects.)

Also wifi transmit peaks are too long to be practically handled by capacitors, so the regulator really needs to supply the full peak current. But it's OK to calculate junction temperature based on the average power and RthJ-A given in the datasheet.

Nominal Animal:

--- Quote from: oliv3r on December 06, 2022, 04:26:32 pm ---But I'll scourge LCSC to find a unidirectional one, as I really do not need the bidirectional of course.
--- End quote ---
Consider the TI TXU0304-Q1, which LCSC says it can ship in 3 days for $0.87 apiece, in TSSOP-14 footprint (0.65mm pitch, but hand-solderable).

I personally buy them from Mouser, where TXU0304PWR costs 0.87€ in singles and TXU0304QPWRQ1 1.03€ in singles, both in TSSOP-14, and well stocked (>18000 and >36000 in stock as of early December 2022).

I just created a small break-out board (15.24mm × 15.24mm) for it in EasyEda, here.  It's in Public Domain, but I haven't used it yet.  It is so simple there should be no risk of goofing it, as you only need the TSSOP-14 TXU0304 chip, and two 0.1µF = 100nF bypass capacitors in 0603.  You should be able to get and populate five such boards for less than ten bucks.

Of course, it is not just for SPI, though.  You can use the same level shifter for UART, and have two unidirectional (A to B) signals on top.  The same board works for TXU0204 as well, in which case the third signal is in the same direction as the fourth, so you can use it for example for UART with hardware handshaking (RTS/CTS).  And for TXU0104, which has all four signals in the same direction.

It might be better to leave the signal names blank (silkscreened completely white), so one could write the signal names on top depending on which chip is being used.  And if you don't care about the ENAble line, you could simply tie it in to VCCA or VCCB.  I left it out, so that one could use a jumper if one wants to tie it to a MCU pin, for example to multiplex SPI buses with devices that do not have or honor the CS pin.  Anyway, Public Domain, so do what you wish with 'em.  No warranties, though, as usual.

Thanks for that, but there's a dime a dozen of those breakouts :)

I was really looking for something tiny, just for the 1 pin (MISO), ideally in SOT23-3, though SOT23-5 can work just as well (GND, VCC-lo, VCC-hi, in, out). But I haven't scoured yet :D

Nominal Animal:
I've used SN74LVC1T45DBV in SOT23-6 quite happily.  These are unidirectional, except that side A has an extra pin that can control that direction.  For one-bit stuff, I'd love to use them still, but they're not easy to find right now; LCSC does have them (TI SN74LVC1T45DBVR) in stock for US $3.28 for ten (and in SC70-6/SOT-363, SN74LVC1T45DCKR, for US $3.31 for ten).

Mouser does have NXP 74LVC1T45GW-Q100H and 74AXP1T45GWH in SC-88/SOT-363 in stock, which seems to be very similar to the SN74LVC1T45 I've used before (except for automotive qualification or the exact logic level trigger voltages, respectively).  But SC70-6/SOT-363 is tiny, entire footprint 2.15mm × 2.40mm, six legs with 0.65mm spacing, so carefulling is needed.  SC-74/SOT23-6 is much easier for me, even if it is just a tiny bit larger (2.9mm × 2.8mm, with 0.95mm spacing).

Whatever you pick, I recommend you get ten even if you now only need one; they are that useful whenever one works with different voltage levels (which for me, is very often).


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