NPR
[Music]
hi I'm the baby I brought to you by did you hear thank you Digi key this week it's mixperia
ladiator what is the new product introduction it's always known as impi by the week this week um okay
uh so this week we're looking at Next Period again uh some Engineers may remember them when they were
called nxp uh they now have a new bitching logo with this like cool X thing going on there uh and
we're gonna look at the nbm 51 and 7100 series of chips these are kind of interesting uh so these
are battery boost chips uh they're little qfns as you see here and uh the flyer which you know
I checked out and I saw this actually posted on social media a couple other people noticed it it's
a very interesting chip so this is designed to be used with lithium coin batteries not rechargeables
the premium metal lithium batteries like CR2032 you know I think there's also like 2016 and then
there's like the 25 40s um they're very small they're very energy energy dense but they have
a couple downsides that makes them tough for use with iot devices particularly ones that have
wireless transmission because you know you have that little burst of energy you need to transmit
the data over Bluetooth or zigbee or cellular or even Wi-Fi or you know ESP now or whatever
your Laura whatever your wireless transmission uh medium is and um if people really like coin cell
bathroom batteries because of their Ultra small size energy density and thinness so you know even
though we really love Lithium Polymer batteries here you know they're a little bit more expensive
than coin cells they do need to be recharged and I have recharging circuitry whereas coin
batteries you know they do have very good density and you can get them at grocery stores and users
can replace them so you know we've seen like the Apple uh location tags the eye tags and the tiles
they use coin batteries they last many many months because they're really smart about how they do
their energy management but then users can replace them very easily and the batteries can be recycled
um so you can pick up your standard CR2032 coin battery for you know 30 cents or less
um these are 3.2 millimeters uh thick and 20 millimeters wide they give you three
volts nominal and they have about like 220 240 uh milliamp hour uh batteries
um these nbm 51 and 71 chips also work with uh these oh man I'm gonna remember that lithium
cyanol chloride these are much more expensive but they're incredibly power dense and they give you
3.6 volts out notice that the even though there's 3.6 volts it's not a rechargeable lithium battery
these are still primary non-rechargeables these are often used for real-time clocks
um or other industrial uses where you really need extremely high power density and you
don't mind spending as you can see they're about five dollars a piece compared to the
um the lithium coin cell batteries but um both of these can be used with the NVM series okay so you
know here's you know showing a good example from the data sheet about when you and why you'd want
to use this so on the left uh you've got your standard coin cell battery lithium manganese
oxide again about you know 240 milliamp hour three volts nominal the cyanol 3.6 volt and you see the
energy density compared to Double A's which are 200 watt hours per kilogram um either lithium
coin Cell lithium metal coin cell batteries have about you know uh 50 percent more um energy per
gram and the lithium thionol has like two and a half times as much so a really big difference
so like why would you ever use alkaline batteries well first off alkaline batteries are you know
very expensive um and they're available also but they're much larger like you know even Triple A's
are the smallest batteries you can get are not anywhere near as small as your lithium coin so
they're not as thin um and of course you need like this the spring holder as well but the
most important thing that keeps people from being able to use coin batteries in a lot of
cases or they have difficulty is that internal resistance that's documented at the bottom
for your alkaline batteries and your Lithium Polymer and ion batteries
um and and most reusable rechargeable batteries your external resistance is really low it's under
gnome whereas for these lithium metal batteries the internal resistance resistance quite high
at the beginning of Life 10 ohms at the end of life 70 ohms so before you even get to
um sorry go to the next image I swap them before you even get the voltage out your current is
passing through what is called the IR the internal resistance which here is modeled as 9 ohms because
in this data sheet for the Energizer battery um they do show you how to calculate it it does you
know it's it's not purely linear depends a little bit under drain and how often you're pulsing it
but basically you know you're it's 10 ohms at least so let's say you're drawing um you know
100 milliamps out to a very small amount of time only for 10 milliseconds so you're drawing 100
milliamps out to transmit data over Bluetooth 100 milliamps isn't too much for your radio
that's going to give you a drop of uh one volt because you know 10 ohms 100 milliamps into the
math equals IR uh your voltage drop is going to be 1 ohm so what would normally be yeah oh no but uh
so what would normally be a three volt output across the battery is across the entire thing
two volts and two volts is probably going to be too low for your microcontroller or radio
to run and so you're going to get really bad performance you're not going to get the distance
you need even though you only needed that current for 10 milliseconds doesn't matter the instant
instantaneous voltage drop is still going to be there so what can you do well um you know
basically don't try to draw a lot of current from a coin battery that that's not what they're good
for instead what you can do is you can slowly sip current off if you're sipping only one milliamp
off instead of 100 milliamps then instead of a one volt drop you're going to get you know
a 10 millivolt drop or something or or less and for a lot of iot Wireless little sensor nodes
they're not transmitting constantly they're only going to be transmitting once every minute five
minutes ten minutes maybe once an hour like those little tile things they don't transmit constantly
they're just kind of saying hey I'm here and then they go back into an ultra deep sleep of you know
a couple microamperes or less of current uh during their deep sleep cycle so what the nvms seventy
one hundred fifty one hundred does as you can imagine is it slowly sips current from the battery
over a long period of time and then charges up this capacitor that it will store the current
charge into and then when your chip needs to you know drag that 100 milliamps out for that
quick burst of Wireless it's like boom I'm going to provide that to you but I'm
providing it to you off of a non-high internal resistance component like a low ESR capacitor
so uh here's how it works you've got the NVM chip here and you see on the left vbt that's
the battery and you have you know stabilizing capacitor there you've got your inductor because
inside is both a buck and a boost converter it's actually boost then buff the voltage gets boosted
up charges that cap on the top right of the schematic the very big c store boost it up to you
know 12 volts because you're um you want to store a high amount of power and the power is going to
be you know the voltage and the capacitance um you know you're for small scale capacitors you're not
going to be able to get really above 100 uh microfarads but you can get higher voltages
fairly easily without a lot of cost so it's easier to boost up the voltage to 12 volts
on the capacitor and then when your my controller says it's ready start you know it needs Uh current
um to transmit it tells the chip the chip converts from the boost mode to the buck mode
and it books down from that charge stored on the capacitor down to your 3.3 volts or 2.8 volts or
whatever you need you transmit the capacitor drains out and then the cycle begins again
so you do have to specify that c-store capacitor pretty well and there's the documentation you can
go through you know all the details basically you know as a rough idea if you're drawing 100
milliamps for 10 milliseconds you need a 100 microfarad 12 volts or 16 volt capacitor uh
you know there's conversion loss 20 here and there and of course you want to over specify
because temperature and the DC offset can affect the capacitance basically you end up with you
know about 100 um microfarads here I think that yeah the calculator here is uh sorry 10 yeah 100
microfarads um and then you also need a bypass cap on the input 10 microfarads to stabilize it and
you can go through it actually you do the math of like how many joules of current you know of power
do I need um so if you remember your introductory to electronics physics classes from college then
uh you know basically doing that math like a problem set in here um we followed the math and
then figure out the capacitor and then you just lay it out and they even show like look you know
here's how big the circuit is compared to your CR2032 um you still have enough space for your
little Wireless chip on the other side or even on the same side the capacitor is going to be the
largest component because again it does have to buffer all of that power off of the transmission
um but it does it all for you and then you know there's actually um two versions of this
chip well there's four versions total so you can program it over I squared C or SPI so we're going
to drive well why do I need to escort cspi you have to tell it for the buck and boost converter
you know what's the maximum voltage and how much current how often you're going to probably use it
and you can set some specifications over I squared to your SPI there's also whether they support up
to 5.5 volts or 11 volts output on the capacitor you know you're going to figure out whether you
need that extra voltage the extra power storage for the a for the 7 series versus the 5 Series
the I squared C version there is also um you while you can configure it over I squared C
it also does free ones so if you're basically you know you don't need to you don't want to tweak and
customize it or if your circuitry just doesn't have it you don't want to have to like boot up
and and configure the I squared C you want to just kind of run on its own the I Square C version does
have a free one so you can choose between the NVM 71 or 5100a and you know you don't have to
set the registers or you can if you want there's also an eval board um that you can use and you
can break off the it's kind of cute if you could snap off the board when you're done um but you can
use it to uh experiment with um different load settings different timing settings and there's
also a PC software that lets you do the I squared C register configurations if you if you so want to
do so again there is a free running mode as well so you know we're both probably wondering and I
just spent a lot of money no it's about a dollar it's um a pretty good deal and then of course your
inductor and capacitor will be he had 20 cents a piece each extra it does at your cost but it could
you know easily triple your expected life because you're not going to be losing um all that power
all that voltage to your internal resistance um by slowly sipping the power and then bucking down
when you need it and sending data over Bluetooth or Wi-Fi or Laura so a really good small solution
for coin cell battery powered projects from did you key in Xperia and let's sign up yeah bye NPR
[Music]