Are there any Espruino 1v4 voltage regulator specifications anywhere?

[espruino-discuss3]

Posted at 2015-02-10 by asez73

Hi, @gfwilliams
It happens that Limetrace sold me one Espruino rev 1v4 some months ago.
As noted in your github's page it has a different voltage regulator than the rev 1v3.

I was wondering what are it's specifications / references?

The idea is to use the ESP8266 as an uart<->Wifi device using it's low power modes described in espressif bbs.
In fact it shows a power peak to 450 mA for a few 30 ms but most of the time it stays far below (70 mA or so). It even can be put in a deep sleep mode at 10nA which is compatible with the general Espruino power consumption in deepSleep mode.

I hope a proper capacitor could leverage this power's peak and let a 'standard' Espruino board run on a battery operated mode.
This could help me produce a wifi sensor device that would connect only once a day or so for 20-30s transmitting it's data and then fall asleep with some recurring measurements done without the ESP8266 being awaken at all.

This also is a side effect of their AT firmware not being open source anymore. Which imply you have to use their modules with either your own firmware or just as an uart<->Wifi device without the benefits of these low power modes on the ESP8266 side.

[espruino-discuss3]

Posted at 2015-02-10 by @gfwilliams

Hi,

The Espruino 1v4 regulator is a Torex XC6202. The datasheet is linked - it'll do 150mA max, so it's possible it'd work with the ESP8266 and a big capacitor, but it could be a stretch.

I'd be really interested to see how you get on though.

The Pico is using the Microchip MCP1703T - unfortunately it's not pin compatible, but it has quite good quiescent current and is happy at 250mA normally.

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Posted at 2015-02-10 by asez73

Thank you!
Yes I think I am a bit too optimistic about a capacitor...
Need to study that but I would be suprised if the capacitor was not more expensive than the usual LM1117v33 and co...

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Posted at 2015-02-11 by @gfwilliams

Yes - although the LM1117v33 does have a 5mA quiescent current - so if you were thinking about running off a battery that's probably out the window.

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Posted at 2015-02-11 by asez73

You are right, finally the MCP1725-3302E/SN seems to be a much better choice with a quiescent current of 120 μA and a maximum current of 500 mA.
Furthermore, it has a shut down pin designed to reduce the quiescent current to less than 0.1 μA which is quite perfect. The Espruino board could control this pin when there is no need to provide power to the ESP8266. In fact, that would be a much more reliable solution than a huge capacitor.

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Posted at 2015-02-11 by @gfwilliams

Thanks! That's a really neat chip. There are loads of uses for a regulated supply that can easily be shut off.

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Posted at 2015-02-11 by asez73

Ok, so digging further there are others voltage regulators which 'could' be of some interest in various contexts:

1. TI reg113-33 Ultra Low Dropout Voltage: 250mV typ at 400mA, Output capacitor not required for stability and HIGH EFFICIENCY: IGND = 850 µA at IOUT = 400mA, Not Enabled: IGND = 0.01 µA
2. Ti TPS73633 Iq (Typ) (mA) 0.4, Output Capacitor Type Cap Free Ceramic
3. LTC3113 Regulated Output with Input Voltage Above, Below or Equal to the Output Voltage, 1.5A Continuous Output Current for VIN ≥ 1.8V, VOUT = 3.3V, Shutdown Current: <1μA. BEWARE output voltage is 3.8V if input voltage is more than 3.0V. I think it could be usefull with 2 NiCD batteries in series.

Clearly those 3 regulators are more expansive than the MCP1725-3302E/SN and they usually don't admit more than 5.5V in input...

If anyone has some experiences to share about this type of problem I'd be quite interested to share.

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Posted at 2015-02-12 by tage

I think that alternative #3 is a good choice. the input voltage range is interesting. I did not understand you warning about that Vout is 3.8V if Vin is above 3V. that is a misunderstanding. what the data sheet is talking about is that it can deliver up to 3A continuous current if Vin is at least 3V when Vout is 3.8V. if you have Vout set at 3.3V you will have 3A available even at much lower input voltage than 3V.

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Posted at 2015-02-12 by DrAzzy

#3 is a considerably bigger deal than the others; it's a switching regulator and requires a number of external components, though in exchange for that, you get higher efficiency, and in that case, the ability to do both buck and boost. Oh, and it's a 20-pin TSSOP w/exposed pad or DFN, and it costs almost ten bucks a pop at digikey.

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Posted at 2015-02-12 by asez73

Hi, yes, you are right:

1. @tage, I did not necessarily read all of the specs correctly. Yet, I read output of 3.8V if the input is more than 3.0V. The trouble, if I am right, is that 3.8V is more than the 3.6V specified for the ESP8266.
2. @drazzy, the real costs of all those alternatives, both in terms of BOM and PCB space, are much higher than the MCP1725-3302E/SN costs. That being said, it is a matter of goal in terms of functionality, more specifically autonomy on a battery operated mode. As a side inadvantage, the MCP1725 could be fitted in the prototyping area of the Espruino board.

And all those components won't support to high an input voltage.

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Posted at 2015-02-12 by DrAzzy

You can fit SOT-23 onto the Espruino Board prototyping area, too (some of those alternatives come in SOT-23-5). The pitch of SOT-23 is slightly finer, but it's no problem.

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Posted at 2015-02-13 by asez73

Ok, I have to purchase some components and make it happen now.