[TriEmbed] Powering ESP32 from an 8v golf cart battery
Pete Soper
pete at soper.us
Thu Nov 19 09:46:30 CST 2020
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]
> *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 <mailto: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 <mailto: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
> <mailto:shanedtrent at gmail.com>]
> *Sent:* Tuesday, November 17, 2020 9:57 AM
> *To:* jwet at mindspring.com <mailto: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 <mailto: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
> <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 <mailto: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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> *Shane D Trent*
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>
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