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<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>Pete,</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>If the high current peaks are a small fraction of the
time, you can "bypass" your way around it- I don't know if the ESP gadgets do
this- maybe you or others do. </SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>There are several systems that do this in either simple
or pretty complex ways. We called these techniques "BFC" for
big fat capacitor.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>If you have a high current spike that is drawn for some
time at some current- the product iT is charge- coulombs. Charge is also
CV, so you can charge up a cap and dump into your load. The simplest way
to do this to have big cap at the load fed by a low value resistor to limit
recharge current to something you can live with. If the duty
cycle is low, you can blast out a big pulse and then have plenty of time to
charge back up before its needed. The problem is usually that
in this simple case, you need to use a much larger cap 10x than just CV
would dictate because while the cap is discharging- the charge is depleting and
its voltage is falling (I/c =dv/dt). To limit the droop to
something liveable, you uses an 8x or 10x sized cap- this way it only droops 10
or 12% over the burst. </SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>The first time that I ever saw this trick was in two
way pagers way back when. The reciever on a pager drew nothing but when 2
ways came out, every now and then, they needed to send a little text
message and that drew a bunch of current. This was the
techniuque. In two way pagers, they engineered in the droop and started
with transmit power kind of dialed back and as the cap discharged, it turned up
the relative power in order to keep a constant total power output. Pretty
clever, this was early days of supercaps but they were high impedance, the newer
ones would be great- like from Maxwell. I think they just used a few
thousand uF tantalum or some kind of nice electrolytic like a Sanyo
OS-Con. </SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>There are quite a few systems that use this trick- I've
seen a lot of hobby (and pro) spot welders that do this. A lot of energy
harvesting systems take in energy as the can until they get enough and then do
their high powered thing and start the cycle again. Walmart had these
little solar powered LCD price tags (about 2 x 1" cell) that worked this
way. The host system had IR emitters in the ceiling that sent
command to the tags. The tags could always receive but they communicated
acknowldgements back to the system with an IR led when they could. The
time budget was something like an hour or something- better than sending a
person with a price gun etc.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>I saw a fancier system at Rockwell Automation- AKA
Allen Bradely. A common problem in industrial is "last gasp" mode on power
failures. In these little PLC's they need to shutdown in an orderly way
and it took someting like a minute. Batteries weren't an option in
most cases due to life. They came up with a clever little discrete circuit
using maybe 4 transistors and an inductor. It consited of a boost
converter that took the 24v and made something like 300v to charge a HV
cap. The same little circuit could turn around and become a buck converter
that could take the 300v and bring it back to 24v when the power failed.
This takes a different tack and uses a pretty nice bit of physics. The
energy in a capacitor is 1/2 CV^2, by boosting up the voltage they could
get this squared energy. Energy is Power x Time, (watt-seconds or
joules). When the engineer showed me his solution, I was amazed and we
couldn't make anything any cheaper or better really.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>I guess the ultimate in this is Xenon flash strobes
though I don't think phones have to rely on this for using LED flash- the
battery has such a low impedance, you just hammer it for a little
bit.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>I have a little Ryobi cordless nailer- I
don't know exactly how it works but the final action is a piston that
runs from an air resevoir. I don't know if it has a
little tiny air compressor that fills up the air resevoir or some
kind of piston run by solenoid to recharge the air. It
recycles really quickly. There is a tear down by AVe on the
web. I need to watch it again. </SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT><FONT color=#0000ff size=2
face=Arial><SPAN class=226354618-19112020> </SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020>If you know the peak current, duration, etc- you can
see if this works for the ESP32. The charge storage IT is good but the
energy storage with the 1/2CV^2 with a buck boost could work probably. I
would think that a regulators like Nick found would be simplest- its kind of
ideally suited excecpt for the 5v max Vin.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=226354618-19112020></SPAN></FONT> </DIV>
<DIV> </DIV><!-- Converted from text/plain format -->
<P><FONT size=2>Regards,<BR>John M. Wettroth<BR>(984) 329-5420 (home)<BR>(919)
349-9875 (cell) </FONT></P>
<DIV> </DIV><BR>
<DIV lang=en-us class=OutlookMessageHeader dir=ltr align=left>
<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B> TriEmbed
[mailto:triembed-bounces@triembed.org] <B>On Behalf Of </B>Pete Soper via
TriEmbed<BR><B>Sent:</B> Thursday, November 19, 2020 10:47 AM<BR><B>To:</B>
triembed@triembed.org<BR><B>Subject:</B> Re: [TriEmbed] Powering ESP32 from an
8v golf cart battery<BR></FONT><BR></DIV>
<DIV></DIV>
<P>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.<BR></P>
<P>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?<BR></P>
<P>-Pete<BR></P>
<DIV class=moz-cite-prefix>On 11/19/20 8:53 AM, John Wettroth via TriEmbed
wrote:<BR></DIV>
<BLOCKQUOTE cite=mid:72D34CFE8C5C482FB4AB6D2A87873B1A@Cheryl type="cite">
<META name=GENERATOR content="MSHTML 11.00.10570.1001">
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=136184213-19112020>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=136184213-19112020></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=136184213-19112020>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.</SPAN></FONT></DIV>
<DIV> </DIV>
<DIV><SPAN class=136184213-19112020><FONT color=#0000ff size=2 face=Arial>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.</FONT></SPAN></DIV><!-- Converted from text/plain format -->
<P><FONT size=2>Regards,<BR>John M. Wettroth<BR>(984) 329-5420 (home)<BR>(919)
349-9875 (cell<SPAN class=136184213-19112020>)</SPAN></FONT></P><BR>
<DIV lang=en-us class=OutlookMessageHeader dir=ltr align=left>
<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B> Nick Edgington [<A
class=moz-txt-link-freetext
href="mailto:nickedgington@edgingtonlabs.com">mailto:nickedgington@edgingtonlabs.com</A>]
<BR><B>Sent:</B> Wednesday, November 18, 2020 6:44 PM<BR><B>To:</B> Josh
Wyatt<BR><B>Cc:</B> <A class=moz-txt-link-abbreviated
href="mailto:jwet@mindspring.com">jwet@mindspring.com</A>; TriEmbed
Discussion<BR><B>Subject:</B> Re: [TriEmbed] Powering ESP32 from an 8v golf
cart battery<BR></FONT><BR></DIV>
<DIV dir=ltr>personal I like the <A
href="https://www.st.com/resource/en/datasheet/ld39130s.pdf"
moz-do-not-send="true">STM <FONT color=#03234b><SPAN
style="BOX-SIZING: border-box; background-size: initial; background-origin: initial; background-clip: initial"><B>LD39130SJ30R</B></SPAN></FONT> </A>which
is a good match for esp32 it will do 300ma with a 300mv drop the quiescent
current is a remarkable 1 ľA in green mode, 45 ľA 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,
<DIV><BR></DIV>
<DIV> The package a somewhat of a pain.<BR>
<DIV><BR></DIV>
<DIV>Nick</DIV></DIV>
<DIV><BR></DIV>
<DIV>I have a number of the regulator board I pictured earlier should you
be near Apex and want one.</DIV>
<DIV><BR></DIV>
<DIV><BR></DIV>
<DIV>nje</DIV></DIV><BR>
<DIV class=gmail_quote>
<DIV class=gmail_attr dir=ltr>On Wed, Nov 18, 2020 at 1:17 PM Josh Wyatt via
TriEmbed <<A href="mailto:triembed@triembed.org"
moz-do-not-send="true">triembed@triembed.org</A>> wrote:<BR></DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex">
<DIV dir=ltr>This is awesome info John, I'm enjoying the read.
<DIV><BR></DIV>
<DIV>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.</DIV>
<DIV><BR></DIV>
<DIV>Thanks,<BR>Josh</DIV></DIV><BR>
<DIV class=gmail_quote>
<DIV class=gmail_attr dir=ltr>On Wed, Nov 18, 2020 at 9:42 AM John Wettroth
via TriEmbed <<A href="mailto:triembed@triembed.org" target=_blank
moz-do-not-send="true">triembed@triembed.org</A>> wrote:<BR></DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex">
<DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2
face=Arial>Shane,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2 face=Arial>There
are a ton and its unfortunately one of these "it depends" kind of
things. But here are a few and why.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2 face=Arial>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.
</FONT></SPAN><SPAN><FONT color=#0000ff size=2 face=Arial>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.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2 face=Arial>Some
old favorites-</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2 face=Arial>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.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2
face=Arial>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.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2
face=Arial><SPAN><FONT color=#0000ff size=2 face=Arial>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. </FONT></SPAN></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2
face=Arial><SPAN>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.</SPAN></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2 face=Arial>Some
favorites lately (doing low cost stuff)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2 face=Arial>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.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2 face=Arial>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.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#0000ff size=2
face=Arial>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.</FONT></SPAN></DIV>
<DIV dir=ltr
align=left><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN> </DIV>
<DIV><SPAN><FONT color=#0000ff size=2 face=Arial>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?</FONT></SPAN></DIV>
<DIV><SPAN></SPAN> </DIV>
<DIV><SPAN><FONT color=#0000ff size=2 face=Arial>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.</FONT></SPAN></DIV>
<P><FONT size=2>Regards,<BR>John M. Wettroth<BR>(984) 329-5420
(home)<BR>(919) 349-9875 (cell) </FONT></P>
<DIV> </DIV><BR>
<DIV lang=en-us dir=ltr align=left>
<HR>
<FONT size=2 face=Tahoma><B>From:</B> Shane Trent [mailto:<A
href="mailto:shanedtrent@gmail.com" target=_blank
moz-do-not-send="true">shanedtrent@gmail.com</A>] <BR><B>Sent:</B>
Tuesday, November 17, 2020 9:57 AM<BR><B>To:</B> <A
href="mailto:jwet@mindspring.com" target=_blank
moz-do-not-send="true">jwet@mindspring.com</A><BR><B>Cc:</B> Pete Soper;
TriEmbed Discussion<BR><B>Subject:</B> Re: [TriEmbed] Powering ESP32 from
an 8v golf cart battery<BR></FONT><BR></DIV>
<DIV dir=ltr>John,
<DIV><BR></DIV>
<DIV>Thank you for your breakdown on voltage regulators. Would you mind
sharing some of your favorite part numbers in the "Modern BiCMOS
LDOs"? </DIV>
<DIV><BR>Thanks!</DIV>
<DIV>Shane</DIV></DIV><BR>
<DIV class=gmail_quote>
<DIV class=gmail_attr dir=ltr>On Mon, Nov 16, 2020 at 5:52 PM John
Wettroth via TriEmbed <<A href="mailto:triembed@triembed.org"
target=_blank moz-do-not-send="true">triembed@triembed.org</A>>
wrote:<BR></DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex">
<DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>There are several classes of dropout that are driven by
the design of the ouput stage</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>Vdropout</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>2v standard bipolar
linears like the 7805 use an NPN darlington output- nice low impedance
and easy to use.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>1v LM1117 type bipolar
linears use a Sziklai modified darlington with an NPN follower driven by
a PNP- pretty good comprimise</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>.5v LM2940 PNP pass element
parts have low dropout but some squirelly stability issues at times and
can have high quiescent at dropout</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>.1v PMOS or charge pumped NPN
pass element types that looks like a small resistance in
dropout. Quiescent can be very low.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><SPAN></SPAN><FONT face=Arial><FONT size=2><FONT
color=#0000ff>.</FONT></FONT></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial><FONT size=2><FONT
color=#0000ff><SPAN>Depending on the type of regulator, there are
subtlties that happen around dropout.</SPAN></FONT></FONT></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial><FONT size=2><FONT
color=#0000ff><SPAN></SPAN></FONT></FONT></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN>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.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN>My 2
cents.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2
face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV> </DIV>
<P><FONT size=2>Regards,<BR>John M. Wettroth<BR>(984) 329-5420
(home)<BR>(919) 349-9875 (cell) </FONT></P>
<DIV> </DIV><BR>
<DIV lang=en-us dir=ltr align=left>
<HR>
<FONT size=2 face=Tahoma><B>From:</B> TriEmbed [mailto:<A
href="mailto:triembed-bounces@triembed.org" target=_blank
moz-do-not-send="true">triembed-bounces@triembed.org</A>] <B>On Behalf
Of </B>Pete Soper via TriEmbed<BR><B>Sent:</B> Monday, November 16, 2020
10:46 AM<BR><B>To:</B> <A href="mailto:triembed@triembed.org"
target=_blank
moz-do-not-send="true">triembed@triembed.org</A><BR><B>Subject:</B> Re:
[TriEmbed] Powering ESP32 from an 8v golf cart
battery<BR></FONT><BR></DIV>
<P><BR></P>
<DIV>On 11/15/20 10:34 PM, The MacDougals via TriEmbed
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