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EPC joined Digi-Key's Anissa Lauer for a discussion about the evolution of semiconductor materials and the factors necessary for another semiconductor material to displace silicon in next generation power conversion designs.
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Welcome to digitise live Google hangout I'm a Nestle! Our product manager at the Tiki today we're hanging out with efficient power conversion.
Discussing the evolution of summit conductor materials currently is becoming more difficult to enhance performance so silicon? Based MOSFETs because of this customers are looking to other technologies to anyways to boost their performance with us today to discuss one of these.
Technologies is EPC to discuss their enhancement mode gallium nitride power. Transistors here from EPC we have CEO Alex lado executive director of application engineering Michael de ROI and marketing director vinegar!
While you are watching a pcs presentation if you have any questions.
Please tweet us using hashtag DK h o a and you will have a short.
Q&A after the presentation now we'll turn this: Over to EPC is up and blow everybody. Out there I'm Alex Leto Rene younger is a to my right and Michael de.
Roy to my left let's get started talking about gallium nitride a pretty exciting.
New technology in the world of semiconductors. Just get started here all right and today we're gonna. Start by telling you about the ideal power switch showing you why gallium nitride is pushes closer and closer?
To that ideal and we'll also talk about when gets ready for you in particular ready now for many people we've been reduction for three! Years and the transition is occurring quickly and we'll give you some demonstrations of some new applications for devices and take. Your questions we've been in this business for a long time I started.
Off with the late 70s making power. MOSFETs and throughout all that time the:
Same questions are asked and the same things are wanted by our customers and the power switch wishlist! Is not change probably in a hundred years everybody wants lower. On resistance this lower on resistance means less conduction losses less eat generated.
Everybody and once devices are faster faster means you get less switching losses and usually it means? That you can make your certain small also less capacitance fascinates has to be charged in discharge.
That adds power dissipation it also adds to the amount energy? The emphasis of life from your drivers to power the transistors folks wanting smaller and smaller is usually cheaper. If you take up less based on your printed circuit board now you can buy less printed:
Circuit board that's pretty expensive real estate and then finally everybody's asking for lower cost so let's see why gallium nitride materially improves. Employees character presence in order to do that I'm gonna start with why gallium nitride and I'm gonna make a comparison? Between silicon gallium nitride and silicon carbide to show you how these wonderful material properties of gallium nitride actually theoretically create his superior device.
There are three main physical properties of the crystal that are important to this discussion. The first one is the bandgap energy and I'm showing. You for silicon in the center of this chart and the bandgap energy is the energy.
That binds the together in the crystal for silicon it's 1.12 well how tightly the atoms are bound in the crystal contributes. To something called the breakdown field that's the second one down and that.
Tells you how hard it is to break the atoms apart and that break down the field! In silicon is point three it also tells you how close you can put terminals together in a device before: They arc and then finally you have electron mobility which tells you how easily electrons float through the crystal now let's compare with gallium nitride and silicon?
Carbon you can see that both gallium nitride and silicon carbide have a much wider band games 3d electron volts. Versus 1 that means the atoms are much.
More closely tied together in the crystal. And what that means is you have a much higher breakdown electric field a factor?
Of 10 better for both gallium nitride and silicon carbide what that means is you can bring your electrical terminals.
10 times closer together and therefore the resistance between. Those terminals will be 110 so not only have you made your device smaller.
But less resistance between the terminals and in fact you can pack.
Ten times more electrons in that small distance:
What that means as you get ten times ten times ten or a thousand times better theoretical? Performance now let's compare the third characteristic the mobility and you can see that gallium nitride has the best mobility: Of all three semiconductor types and that means the electrons can scoot around with the least amount of resistance.
This translates into a graph that we're showing right now we're on the vertical axis we put the on resistance of a 1 millimeter square device?
That theoretical best on resistance you can get for that device for a given breakdown voltage and the breakdown voltage is on the horizontal axis and we've! Drawn where epcs gallium nitride Egon fats are on this theoretical curve silicon in the upper left is the least efficient of the three.
Materials today after 35 years of producing power mosfets you can actually buy power MOSFETs right on that theoretical limit? And you can see that EPC is already a factor of three to a factor of ten.
Better than the theoretical limit for silicon with our early generations of enhanced both gallium nitride field effect transistors and as the technology! Improves we follow that era and get closer and closer to the gann? Look and you can see the gallium nitride is superior to silicon carbide and that's because:
Of the mobility of the electrons that. We saw in the prior slide so what is this feat. Well for one thing it means the egan effects.
Are smaller and I'm showing you a comparison between an. Actual silicon device and an equivalent en fat now you can't that is is is much smaller if you looked at the silicon device inside this package:
The Egon if that would still be five times. Smaller but why do I show it compared to a packaged transistor. That's because our Egon feds do not require the bulky cumbersome and expensive.
Plastic packaging that are required of silicon transistors so this is a real comparison of how much space it would take on your? PC board for equivalent performance so you get bets are much smaller Egon effects are much faster today. And on this graph I'm comparing a common figure of Merit or fom where.
You multiply the on resistance of the device. Times the charge that it takes to apply to the gate to turn it from?
On to off or off on and this R cubed product the smaller is the more efficient that device is relative to other! Products and here are comparing against the state-of-the-art in silicon power MOSFETs you have Infineon international rectifier silicon expand. Fairchild devices represented here and our EPC 2001 100 volt again fat on the far left and it is at times!
Better than the best silicon in the world that translates into efficiency? And in this chart I'm showing you the efficiency of a point of load converter.
One of the most common types of power supplies you can find in this world on the vertical? Axis the efficiency of this point load controller on the horizontal axis the output current and we're. Comparing MOSFETs again starting against them again we picked the best MOSFETs in the world and this!
Is 12 volts in 1.2 volts out operating at one megahertz switching. Frequency and you can see the Egan FET point alone? Converter is a full three to four points better than the had been the MOSFET.
Epc
Based this is showing the family of devices our second generation of products. Are listed on the Left they range from 40 volts all the way up to 200 volts from 4 milli! Ohms all the way up to 100 milliohms comes in five different die sizes just recently we introduced a a middle.
Sized die size from showing highlighting here the epz 2016 and you can see the various. Features of this chip scale package these devices. Have interleaved drain and source electrodes they're soldered.
Bumps and then there is a gate in the substrate in this intermediate. Size it's 2.1 millimeters by one point six millimeters that's pretty tiny and that produces a hundred both device with! A 16 milli ohm on resistance also in the last month we introduced the two!
Zero one eight 150 volt intermediate voltage a device which I'm highlighting. Here again interleave drain and source gate and substrate electrodes it's it's three point.
Six by one point six millimeters and it's 25 milli ohms these parts are available today by pushing the Buy.
Now button on our website are going to digit key and buying it off the. Shelf there a few weeks ago we introduced our third generation of Eagan fats these devices are faster and a better figure of Merit:
Than our second-generation parts they ranged with 40 volts all the way up to a hundred volts.
And we sized them to be much smaller than the second generation part so you. Can see the on resistance ranges from 125 all the way up to 500 milli ohms and that's because we're aiming.
At smaller power level applications such as envelope tracking and wireless power the capacitances or charms? The gate charge the drain charge they're all much much smaller than our second generation devices and the product of on resistance times charge is also.
Improved what does this really mean but means! That these vices are fast as can be now let's give you an example now we're gonna talk about a buck converter. This is the EPC 9 107 demonstration board which is available today from digit 8 or through?
An EP C's website I ended a hit it uses two of these EPC 2 0 1 5 he ganz bets. They're 40 volt fats and I'm showing you a switch node waveform from this power supply and you'll:
Notice that the rise time from this demonstration. Board is about 1.1 nanosecond and 15 amps.
That is pretty fast especially when you consider that the driver IC which is the Texas Instruments ln 5 1 1 3. Is switching in 1.2 nanoseconds so these parts are transitioning faster than their driver IC also you'll notice.
Because of the very efficient layout that there is only.
A 3 volt overshoot at 15 amps so we have a 28 bold signal here with 3 volts of motor. Overshoot and that is approximate very efficient very tightly here's the efficiency you can get from this from this demo board in black we have. 12 volts in in red we have 24 volts in all of them 1.2 volts out and they're all.
Operating at one megahertz and we're comparing it against the best MOSFETs. We can find as you can see there's several percentage points difference in efficiency:
Between our gig and fence and any MOSFET that you can get out there plus you can go all the way up to 24 volts me and. Put in 1.2 volts on the output and still get 84 85 percent efficiency so what is the time.
To convert when is the time to get rid of those aging power MOSFETs and go with. Meighan fast well over the last 35 years we've had experience with MOSFETs. Converting over from old bipolar transistors and we found that there are four main things.
That control the rate of conversion of a new technology. In the semiconductor world first of all did it enable significant new capabilities if it did those were the early adopters.
Those were the the applications that converted immediately because there was no other way to do it secondly is it easy to use.
The easier a new product or new technology is to use the more likely an engineer can get their first generation or first passed:
A system to work well the less amount of word it takes? The less amount of time it takes therefore the more. Likely it is that these devices will be used third is it very cost effective to the user because in the end nobody's.
Going to convert and make their system cost more as a result and finally. Is it reliable these products aren't reliable enough! For the application there's no reason to convert no matter?
How much encompasses so let's take a look at some new capabilities the the Egan fat which has been around for about three or four years? Is primarily enabling applications that require high speed couple of examples are envelope tracking and wireless power you'll see a demonstration!
Wireless power in a minute and our third generation he and feds are a good.
Illustration that on your left-hand side of the chart is an actual. Waveform of our EPC 8007 driven by an LM Phi 1 1 3 driver from!
Texas Instruments this is on our new demo board that you. Can buy from digi-key on 9 0 to 7 and the rock has and fall times on this are. Each about 1/2 a nano second even though the driver IC is putting.
A gauge signaling as a rise in full time. A 1.2 nanoseconds these parts are switching in half the time of their own input signal half a nano second this is the first time you can. Power you can switch this kind of voltage this kind of power level in some nanoseconds:
Feeds and as a result of the higher gain on the right-hand side of this chart you can see the gain curve versus frequency. For the 8002 another member of our generation 3 family and at 1 gigahertz. We still have 22 DB of gain 11 DB of gain at 2 gigahertz and in fact a little over 7 DB gain at 3 gigahertz so:
These parts can be used well into the gigahertz range they can be used to make switching power supplies? Well in the tens of megahertz are they easy to use well there are just like a mosfet: EP C's enhancement mode gallium nitride FETs were designed to look just like a MOSFET except there are a couple of things.
You have not be keeping them these parts are very high frequency part and a high V capability makes them more sensitive. To circuit layout EPC has many papers on our website and our demo boards as well that use very very special layout techniques. In order to reduce or to reduce ringing and make?
These devices perform with extremely high efficiency second. Thing is that the eighth a little bit more sensitive? Than our lost bet it is a maximum voltage 6 volts of the gate beyond you can.
Damage the device before you need appetite. Regulation on the gate because it takes about four and a half bowls to turn this part on then the new IC is about. In the marketplace such as the need LM 5 1 1 3 or the LM 5 1 1 4 from Texas Instruments uh chef regulate.
This gate voltage make it easy to use of course one of the things that makes these. Egan fence easiest use is if they're available right now off the shelf from digit key order. It now you can get it tomorrow are they cost effect the answer is that today.
You get feds are a little bit more expensive than in Austin but let's look at how that how that goes into the future: And in order to do that I'm gonna compare the cost of a silicon wafer!
Versus a an Egan wafer now silicon MOSFETs and Egan.
Pets are all built on on wafers and these wafers. Go through a wafer fab and if you build one of these wafers on gallium nitride vs. so I can even compare.
The cost by looking at five elements starting material growing the epitaxial crystal the case of gallium nitride that's gallium nitride. In case of silicon and silicon Oh fabricating.
It in the wafer fab where you put. Masks and you etch them and all sorts of things.
There you test them you assemble when you add it all up that's the that's the cost of comparisons: That we're looking for and in 2012.
We can look on the on the. Chart here and see the starting material is the same well that makes sense because both are egan wafers and silicon! Wafers start with a silicon week but the EPI growth in EDM growing this gallium.
Nitride crystal on top of silicon is more expensive. Than growing a silicon crystal on top absolutely the wafer fab costs are the same and that's because our egan process. Is much simpler than silicon but we're still running at lower volumes testing is the same and assembly.
For an Egon fat is half the cost of a silicon mosfet. The reason is we don't need a package: And the silicon mosfet reject is half.
The cost so what about the future well we are working with various equipment manufacturers to make a next-generation machine for grown gallium nitride Fe and we believe. That by 2015 we will have the cost substantially the same as growing silica net at higher volumes our wafer fab cost be lower and overall: In 2015 we believe that you can fast will cost significantly less than of silicon power austin but are they:
Reliable and the answer is yes we have millions and millions of hours of high stress testing. Behind us now this is just showing you a few selected charts.
On the upper left you can see the armed resistance after a thousand: Hours of burning under maximum stress on the upper right you can see threshold voltage in after a thousand hours you can see on the lower left a power supply: A series of power supplies that were run for 3000 hours under maximum.
Stress and on the lower right you can see our devices chip scale devices that were stressed four thousand.
Hours with Maxim voltage on them and high: Humidity environment so even though there's not an encapsulation inside of epoch see our our bairdi can last. For thousands of hours and even a high:
Humidity environment so yes they are alive now let's go to a product demo I'm going to turn it over here. To Michael de Roy who's going to show you some new applications for our Egan fence!
Hi everyone thank you Alex today I'm going to demonstrate. Two systems the first is a wireless. Transfer technology it's very exciting technology that's emerging today particularly for the cell phone mobile device charging market and in this instance we're gonna.
Have to demonstrate the this board here which is a loosely coupled this consider loosely coupled where the to the source on the device have some. Separation between them and it is operating. At six point seven eight megahertz which is the lower is TM frequency band in this demonstration here.
I have a source board I have a source. Coil I have a device board a coil and a device or as you:
Can see I've powered it up and I have this little hockey puck with.
An LED in it and as I bring a closer.
Here you could see how the light is turned on as I bring it further away it has this energy.
There this system has a peak efficiency of around 70 percent using the gallium nitride transistors and when we built. The same system with MOSFETs equivalent MOSFETs.
We're getting around 66 percent efficiency and that is giving the gallium nitride version a four percent advantage. Point next I'll demonstrate the Class D audio system here we have a bridge tied load a stereo clasp the! Audio system it is capable of 150 watts into a dome.
Speakers or 250 watts into for our speakers the system uses the epc 2016 devices. And the LM five one and three gate driver this system has no heatsink and can operate at full power! Without a heatsink I'll turn it on and play some music for you and turn up the volume.
Unfortunately the stage of the link doesn't do it justice but we'll. Talk about why do again feds offer? Us a superior class the audio system the no Mahon.
Resistance coupled with the lower half the capacity of these devices offers higher efficiency and lower distortion of the switching white foam and that translates.
Into a higher damping factor or low open-loop output impedance those are critical factors when looking for total harmonic distortion that is imposed. On the audio signal all right well we want to reverse apologize for Michael selection easy but other: Than that we're gonna move back back and show you a little bit about our products.
Okay so you just heard that the future of semiconductor materials.
Is here today and you're ready to get started I'll be PC and digiti make that really easy for you to do with. A full line of development boards and demonstration circuits sock the digiti even get it started right away for every product voltage.
We have a half bridge development board this is a partial circuit essentially the power.
Block that contains the Egan fetch and average configuration with. Onboard gate drive dead time control and the optimal layout so we've taken care of all the critical components:
You can get a really quick easy evaluation the switching performance of these sentence the latest additions?
This family is the EPC nine zero to seven which features. One of our latest Gendry and feds the 40 volt EPC 8007 we also have a growing.
Family of full demonstration circus these are complete.
Converters and inputs cases are closed loop the latest addition that we were talking about earlier?
Is the d9 1:07 which is a 28 Volt to 3.3 volt buck converter operating out of megahertz and using our optimal layout. Techniques now we make all of the design files for art for our board available on our website so if you go to EPC co.com this. Is what the front page of our website looks like and if you click on to demo boards down.
Here in the EPC store behind the full listing of development boards and demo circuits along with all of their.
Design files available for download which you click on the Buy Now button today you can have your board delivered tomorrow from tajiki.
Okay alright thanks very much and I think now we're ready to take some questions ok the first question coming through what. Are the key advantages of APCs enhancement mode transistor?
Is compared with power MOSFETs the biggest: Advantage that people find is that they are so fast and that enables. New applications but in addition to being fast they're very small and so people have been able?
To miniaturize their systems what a load converter is and half the size and and the size! Compared with the high speed they reinforce each other you can get very small inductors and capacitors. Because you're offering higher frequencies and and of course they're pretty easy to use and they're immediately available ok we have another question.
Does the again have a body diode how does it compare to silicon MOSFETs and forward voltage drop reverse recovery characteristics.
Yes it does have a body diode and I'd like to just take a second and show. You what it looks like I think. I have a picture here to show you how it operates just give?
Me one second and we'll see it it states the seconds which. Are under this here we go vinegar so how does the diode work so this is the part of our seminar.
That we're giving around the world right now and this is what a cross-section cartoon. Looks like of our en FET on the left you can see a source of the right you can see a drain and those little circles.
With minus signs represent the electrons that are everywhere except underneath the orange cake now if you apply a positive? Voltage on the gate it will bring the electrons. To the surface because opposite charges attract and that's why we call it enhancement mode you.
Have to put a voltage on the gate to get the electrons to complete.
This circuit now if you look at this device from the other direction you can see that applying a positive voltage from the drain: To the gate would do the same thing sucks the electrons up and therefore it conducts just like a diode in the reverse direction.
Except the mechanism is different in a power MOSFET it actually uses a PN Junction diode and that's actually. Pretty inefficient because it has minority carriers what that means is that you're gonna have a reverse recovery time from these minority carriers that have!
To die away slowly in our en fence. We don't have it and therefore you have zero qrr or recovered.
Charge one disadvantage is that this diode has a slightly higher forward drop and I'm showing you the drain source or the source drain.
Current on the vertical axis compared to the source drain voltage for the diode drop on the horizontal axis. And you can see for an Egon fat it's somewhat higher than for a MOSFET and therefore if you're. Using the diode a lot the forward drop will give you well it will it will be more inefficient?
With an Egon fat but you have no reverse recovery charge and therefore you will gain efficiency. From that in general it's more efficient?
To not use the diode either MOSFET or negan all right what kind of questions? Do we have coming up how do I assemble a pcs enhancement mode Gant transistors I think we actually: Have a some some good stuff on our website and I'm gonna go to our website and and show that?
To you here in one second take a look at this so if you are doing a front.
Page of our website you'll see the the storefront.
And you'll see also a library on the left and one of the books says assembly resources. Click on that book you'll get to a landing page that has a series? Of articles and videos that show you not just how to assemble but how to disassemble.
This stuff and of course they're starring. Our own Michael Deroy and he plays no music in the background so that very good we also quick reference guides that! You can get which are good for if you're if you're.
Trying to get a technician in your engineering lab to to follow a recipe.
Formula these should give that to you I can add to that for production we put a lot of information in our data sheets: On how to design the pad solder mask and the stencil so following. Those guides most of the manufactures we've.
Work with have being very successful at sending out devices to the ports I think we have another.
Question up here and that's uh let's see paralleling how about parallel well the devices do parallel quite well I and his matter!
Of fact you can go back to our website and you'll find. It in the same place under a Gantt: Fed basics and if you click on that you'll get to landing page for vet basics and you have to go into design basics that's?
Where we are we're designing and then you'll find a whole tutorial on how to pair all you get events! They're actually quite amenable to paralleling and in fact we have a demo board what's the number on that. The PPC nine one zero eight nine zero one seven has parallel he can't fence.
In it so you can actually buy a demo board that has them on it or read our article. And you'll see how to do it it's very straightforward okay there's another question can I design my PCB with. Again fence with only two conductor layers I think the answer is yes you can we we again under design.
Basics you'll see layout techniques and I'll show you various ways of doing it the the new devices.
That we've just come out with our generation? Three are particularly laid out it's being extremely.
Efficient in a two two layer PC board in general we find our car engineers want to use more layers for more. Functions and features but it can't be done with two can we have another question the high frequency cap of the devices.
Could be an issue with layout of my circuit board what must I be mindful of laying out my circuits. Michael yes okay I'll turn it over the:
Real well the high frequency cap you you got to keep in mind needs to be low the equivalent series inductance. That's the first key we'll look at so in general the devices that we're working with are very small so the bus capacitor that.
High frequency capacitors will also be small and you want to choose capacitors that I've got a low profile. Profile that will also keep the inductance.
Down and then in terms of that if you follow our guidelines for the optimal layout it will also help you to keep the inductance in the loop.
