[TriEmbed] Powering ESP32 from an 8v golf cart battery

Wed Nov 18 12:17:31 CST 2020

This is awesome info John, I'm enjoying the read.

>From personal experience, the ESP32S (and ESP8266) can be pretty power
hungry when the radios are on, and are particularly sensitive to
brownouts... I try to use something with at least 300mA and with good,
stiff caps.

Thanks,
Josh

On Wed, Nov 18, 2020 at 9:42 AM John Wettroth via TriEmbed <
triembed at triembed.org> wrote:

> Shane,
> There are a ton and its unfortunately one of these "it depends" kind of
> things.  But here are a few and why.
>
> Most of the stuff I do is pretty small, low current stuff and 2.7 or 3.3v-
>  an 8 bit uP and a display with some RF.  Very low quiescent parts
> suitable for circuits with sleep mode, etc.  A lot of my stuff lives
> outside and runs on a 12v battery so I try to shoot for -40C operation and
> 16v Max vin.  Temp range matters for capacitors mostly and dropout.  I buy
> almost exclusively from Digikey.  Their search engine and service is
> amazing even if they cost a bit more.  I tend to design very low power
> things and like low Iq for sleep operation.  Generally very low Iq means
> poor HF rejection (you need loop gain)- in RF stuff, I'll compromise on Iq
> and shut the block down, etc.  I prefer newer parts, there has been so much
> progress in the last 15 years, its amazing- there is no reason to use a
> 7805 for any real design- even cheap stuff.  There are better and even
> cheaper alternatives if you're building more than a few hundred.  At low
> volumes, 7805's can be awfully cheap but they're really only designed as
> 60/120 Hz type regulators in a traditional AC supply.
>
> Some old favorites-
>
> Micrel (Mchip owns Micrel linear now) MIC5203, 5205 series of BiCMOS
> types.  PNP pass element but controlled drop out current.  16v  50/150 mA,
> Iq 1 mA max.  Micrel invented BiCMOS pretty much and its good to see that
> Microchip is keeping a lot of their parts.
>
> Microchip 1791 is a great HV regulator- 30v max in, 70 mA out, load dump
> (48V), Iq 70 uA.  Microchip makes tons of cheap analog parts these days and
> lot of good linears. They acquired Telcom semi many years ago which was a
> big CMOS linear company (like Maxim). Newer CMOS stuff is good but the
> older stuff is not so good- done on large processes and traded Low Iq for
> performance- very slow load and line transient recovery, no PSRR, etc.
>
> Toko TK11625 and TK1150, Digikey dropped Toko but I still have a lot of
> these around- they're officially obsolete but they're plentiful everywhere
> and there are newer alternatives. Available in TO-92, 100 mA, Tk71150 is 5v
> LDO with good HF rejection for low noise for a  post after a switcher,
> Quiescent is OK at 300 uA,  Seiko makes similar BiCMOS parts, can be hard
> to find these days.  Microchip basically copied these regulators to create
> their line and DigiKey wants to keep Mchip happy.
>
> TI TLV1117 A "special" very low Iq LM1117 variant, quiescent of 100 uA.
> Better PSRR and dropout.  Good in 3 Alkaline of 1 LiIon to 2.5v apps.  Max
> Vin is 5.5v, only downside.
>
> Some favorites lately (doing low cost stuff)
>
> Diodes Inc AP-7381 series.  Available in TO-92 option still for quick
> perfboard builds and breadboard.  Cheap.  Very low Quiescent, 50/150
> mA variants.  Digikey large stocks always.
>
> ABLIC S-812Cxx series.  1uA Iq, 10-100 mA output depend on voltage.
> Quiescent useful for running a real time clock or deep shutdown on a HV
> input.
>
> Anything that Maxim or LTC/ADI makes are invariably awesome but low volume
> pricing (<10k) is awful.  Real customers pay nothing like those prices
> believe me.  I have odds and ends of Maxim leftovers but never have what I
> need.  TI has better pricing but isn't innovating much in this area- the
> TLV1117 is an exception- excellent.
>
> In your Golf Cart app, what's your load current min and max and vin min
> and max. Any big line or load steps? Temp range and size could help too.
> Any special operation needs like sleep?
>
> After 25 years in Standard Products at Maxim, I can talk Linear IC's more
> than anyone cares to listen.  Take care- shoot me a private mail or call if
> you have specific questions.
>
> Regards,
> John M. Wettroth
> (984) 329-5420 (home)
> (919) 349-9875 (cell)
>
>
> ------------------------------
> *From:* Shane Trent [mailto:shanedtrent at gmail.com]
> *Sent:* Tuesday, November 17, 2020 9:57 AM
> *To:* jwet at mindspring.com
> *Cc:* Pete Soper; TriEmbed Discussion
> *Subject:* Re: [TriEmbed] Powering ESP32 from an 8v golf cart battery
>
> John,
>
> Thank you for your breakdown on voltage regulators. Would you mind sharing
> some of your favorite part numbers in the "Modern BiCMOS LDOs"?
>
> Thanks!
> Shane
>
> On Mon, Nov 16, 2020 at 5:52 PM John Wettroth via TriEmbed <
> triembed at triembed.org> wrote:
>
>> I'll put my 2 cents in here for a few subtleties.  I defined
>> probably 1000 different linear and switching regulators at Maxim in my 25
>> years.
>>
>>
>> Vout plus dropout is pretty good overall.  But don't forget that dropout
>> is defined where the output voltage drops 100 mV.  Its coming out of
>> regulation and all the goodness that linears give you stops happening.  You
>> also want to do this at max load, max output tolerance and worst temp.  The
>> drop out for bipolars decreases for higher temps which helps but at very
>> cold temps, it can grow- a lot a very cold.  This is not allways well
>> specified.
>>
>> There are several classes of dropout that are driven by the design of the
>> ouput stage
>>
>> Vdropout
>>
>> 2v      standard bipolar linears like the 7805 use an NPN darlington
>> output- nice low impedance and easy to use.
>> 1v      LM1117 type bipolar linears use a Sziklai modified darlington
>> with an NPN follower driven by a PNP- pretty good comprimise
>> .5v     LM2940 PNP pass element parts have low dropout but some squirelly
>> stability issues at times and can have high quiescent at dropout
>> .1v     PMOS or charge pumped NPN pass element types that looks like a
>> small resistance in dropout.  Quiescent can be very low.
>> .
>> Depending on the type of regulator, there are subtlties that happen
>> around dropout.
>>
>> Old bipolar regulators like the 7805 have a drop out of about 2v
>> conservatively.  The output is an emitter follower darlington stage which
>> is 2 vbe's (.7v each) and 2 Vce sat (about .2v each).  This is about 1.8v.
>> Since the output is a follower, it has a gain of 1 and are generally very
>> well behaved with very little thought given to bypassing and stability.
>> High frequency rejection is poor and accuracy is somewhat poor.
>>
>> First generation  bipolar LDO's like the LM2940 etc, used a PNP output
>> stage with a grounded NPN pulling its base down.  These parts have two Vce
>> sats in the dropout path (about .5v).  These  transistors have gain on top
>> of the error amp gain and get unstable without following the the bypassing
>> instructions closely.  The output cap becomes the dominant pole and the ESR
>> of the output cap has to in a specific range- neither two small or two
>> large.  The other annoying feature of this class is as you approach
>> dropout- the beta provided by the PNP pass element goes south and they can
>> draw lots of current at or near dropout trying to keep the PNP in
>> saturation.  In low power circuits, this can cause a sort of latching
>> action and flatten a battery in no time.
>>
>> The LM1117 type second gen bipolar LDO's have a NPN follower ouput.
>> These have the benefit of a follower but only moderate dropout
>> performance.  They were basically invented to make 3.3v from 5v which a
>> 7805 couldn't do.  Good for point of load but kind of mediocre otherwise.
>>
>> Modern BiCMOS LDO's generally have a PMOS pass element and some MOS and
>> Bipolar circuits..  These can have very low quiescent, very low noise and
>> the lowest dropout possible.  They are also pretty stable with most loads
>> but take a signicant cap on the output usually.  Something like a 10 uF
>> ceramic.  Microchip make some good  low cost parts in this class.  Probably
>> my favorites.
>>
>> There are all CMOS LDO's that share most of features of the last category
>> but don't get the low noise and high accurancy generally.
>>
>> One other issue is your 8v battery.  The charging voltage on a Lead Acid
>> could be over 10V which is a common abs max for many linears.
>>
>> My 2 cents.
>>
>>
>>
>>
>>
>>
>>
>>
>> Regards,
>> John M. Wettroth
>> (984) 329-5420 (home)
>> (919) 349-9875 (cell)
>>
>>
>> ------------------------------
>> *From:* TriEmbed [mailto:triembed-bounces at triembed.org] *On Behalf Of *Pete
>> Soper via TriEmbed
>> *Sent:* Monday, November 16, 2020 10:46 AM
>> *To:* triembed at triembed.org
>> *Subject:* Re: [TriEmbed] Powering ESP32 from an 8v golf cart battery
>>
>>
>> On 11/15/20 10:34 PM, The MacDougals via TriEmbed wrote:
>>
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>
> --
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> *Shane D Trent*
> Patent Agent
>
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