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

Thu Nov 19 13:16:52 CST 2020

You have a huge inductor in the motor, which will put huge transient spikes
everywhere, and that includes the places you don't want them. I am not sure
you can overdo the isolation. Al the rules apply single-point grounding, Pi
networks of L's and C's are a good start. An isolated DC-DC converter would
not be overkill.  I am sure you mention it but what is the bus voltage out
of the battery.

Nick

On Thu, Nov 19, 2020 at 10:46 AM Pete Soper via TriEmbed <
triembed at triembed.org> wrote:

> Thanks for sharing, this, John. The other day trying to gauge how much
> Paul's golf cart battery would be drained with a linear vs switching
> regulator a very quick glance of ESP32 stuff gave a guestimate of about
> 4.7V*50mA (but I guessed this wasted power wasn't relevant to Paul). But I
> hadn't thought at all about peak currents as they relate to regulator
> choice, and more importantly how much time is spent at those higher
> currents.
>
> But I'm writing to wonder how much help decoupling the regulator and
> minimizing inductance might help with transient scenarios like you describe
> below? Or would the cap dumping current just fake out the regulator and
> simply make the droop happen a little later?
>
> -Pete
> On 11/19/20 8:53 AM, John Wettroth via TriEmbed wrote:
>
> That's a nice part Nick.  Like a lot of modern parts on small process, its
> kind of designed around one LiIon cell operation.  I like the "green mode"
> stuff.  LTC and Maxim make some parts like that.  The difficulty with
> switchover type parts is when you have a big load transient (eg- a transmit
> burst).  If the part is in the low quiescent mode, it can droop and cause
> havoc.I noticed it has a forced green mode pin which could alleviate this
> with some thought in software.  A lot of times, its easier to have a
> seperate regulator for the high current case or if they can be split up.
>
> I didn't realize that these ESP devices require so much current, I've only
> played with one on the bench pretty casually.  For the 8v input case, you
> really might want to consider a buck converter unless the high current only
> runs very intermittently.  The power wasted in a linear could create
> potential heat problems.  You're talking about getting rid of 1.5 watts
> from your 8v source.
>
> I agree with Nick on those DFN packages- awful, you're into hot air or
> oven reflow.  I like parts that come in a variety of packages including
> through hole, this is getting rare these days.
>
> Regards,
> John M. Wettroth
> (984) 329-5420 (home)
> (919) 349-9875 (cell)
>
> ------------------------------
> *From:* Nick Edgington [mailto:nickedgington at edgingtonlabs.com
> <nickedgington at edgingtonlabs.com>]
> *Sent:* Wednesday, November 18, 2020 6:44 PM
> *To:* Josh Wyatt
> *Cc:* jwet at mindspring.com; TriEmbed Discussion
> *Subject:* Re: [TriEmbed] Powering ESP32 from an 8v golf cart battery
>
> personal I like the STM *LD39130SJ30R*
> <https://www.st.com/resource/en/datasheet/ld39130s.pdf>which is a good
> match for esp32 it will do 300ma with a 300mv drop the quiescent current is
> a remarkable 1 µA in green mode, 45 µA in normal mode which matched with
> the ULP mode on the esp32,  Not a problem with a golf cart but important
> for low power sensor. and to top it of STM will send you a couple for just
> the shipping cost,
>
>  The package a somewhat of a pain.
>
> Nick
>
> I have a number of the regulator board I pictured earlier should you be
> near Apex and want one.
>
>
> nje
>
> On Wed, Nov 18, 2020 at 1:17 PM Josh Wyatt via TriEmbed <
> triembed at triembed.org> wrote:
>
>> 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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>>>>
>>>
>>> --
>>> [image: photo]
>>> *Shane D Trent*
>>> Patent Agent
>>>
>>> 919-348-0061 | shanedtrent at gmail.com
>>>
>>> ShaneTrent.com | Skype: skype:shane.trent1
>>> <#m_-2812097307455768919_m_133033098193379331_m_189338381597980778_SignatureSanitizer_SafeHtmlFilter_>
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