Gadgetory

everyone so we were talking with Asus about power design and I said you know what let's let's stop this and record it because a lot of this is over in my head so let's just get it on camera and go through it for viewership as well and I'm joined by Jonathan from Asus he's an ro GPM write work on the ROG products and we're gonna talk through some transient response some load line briefly things like that on vrm design it's really interesting information gives you a basic like a primer on the types of things ACS has to think about when they're building a PRM and so I guess we'll just point out here that this is really top-level stuff there we're not talking like specific use cases or edge cases or anything like that we're just primer only yeah so don't don't go and try to design a vrm with this because you'll need a lot more information well go through the basics today should be pretty fun and hopefully we'll have more content like this before that this video is brought to you by us and 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gets a little bit confusing because people a lot of people think that like adding more phases is better and this is true because when you add you know a second peter fourth PWM signal here you have to add a fourth power so now your power load is split between four components into three right and so when you add more face technically it's it's it's bad performance therm only better but when you're talking about the phase you're actually talking about the control signal how you're controlling so in our solution right now we're actually kind of using like more power stages per P double control signals running in parallel and that spreads the load while on you know removing the doublet which you know introduced some delay you know just an example at these two boards so you've got I think these are like the same board right except the prm's changed yeah so you've got a twin and and then an extended phase design yep so the heat load on the e-zine what does it look like thermally is it is it basically do they end up looking the same thermally or is like or just twin perform better or a while yeah so both of these right since the the components that are used are exactly the same the power spread across the same area and the difference is actually over here you can see these you can see these little tiny eye sees right yeah those are the doublers right so basically these had a little bit of heat but that's just like icy efficiency right virtually nothing okay so that's like kind of negligible but then over here is you know the toe ball comes in over here passes through these components and then this then goes through you know the bicho kind of provide power ultimately to the CPU right and we were else talking at how you've got the caps kind of evenly spaced you know your your power your a pen power can I just can't necessarily always be closest right you're over here right so when it comes in over here by the time you get to this part of the power plan there's a bit of like they can be like some our drop or like you know sometimes like the power doesn't distribute perfectly evenly across this entire distance okay and so we these capacitors kind of act as many batteries to hold the charge hold the charge and then like distribute it when necessary right right now these also function as you know ripple of ripple filtering right which is necessary if you know if you're using fewer phases right because this is something that is a weakness you know when you do have less faces this is electrical we can get into that in a little bit okay detail later but if you're concerned about thermal performance right what you really need to look at is how many power stages you have and if power stage is basically an ICU that comprises of a driver high side MOSFET and a low side MOSFET and actually between those three components the driver itself actually doesn't add any additional heat okay the fact that the driver is integrated with the high side low side MOSFET the impedances they can all be kind of tuned to be more more ideal for each other right so it's a more efficient package overall okay there's two things we were talking about mainly there's ripple and then there's transient response or I guess right these are the two parts that kind of cover the electrical performance part of okay all right and we just need to make sure one that I understand what you're talking about and then to that the viewer is how much time you're talking about so we'll go through I guess top level of ripple and a transient response so yeah this is the other half to kind of more phases as batteries because when you have more phases right they turn on kind of interns right right then basically so 6:16 phase on the bright-red yeah and then this is actually like the amount of ripple and you see it's not it doesn't remain constant across all duty cycles it changes hmm and this is actually like for example like the the equation for in pull rebook ripple current you can see it depends on the phase number it's the current over and phase number yeah and this is a maximum current I'm going this is the duty cycle okay right and so you can see over here like when you you know when you have less phases fewer phases right ripple is worse and as you get higher though you kind of see from 8 to 16 it kind of starts getting into a diminishing returns right and then right this is what we were talking about with the capacitors earlier where you can have input filtering also to kind of reduce like you know the input current to kind of not reduce it but to buffer the input input current and you know in general right like one capacitor ours is rated for five five thousand lamps which is you know so we've got a ripple current of under 16 on for phase 15 15 amps over there poor face yeah and so then you know you won't need as many capacitors as what we put on the board itself right which is why you know sometimes you might see like okay like one generation has fewer technical phases than another one right but the capacitance have remained the same is because you know the primary reason for why we're using those capacitors is actually not because ripple is an issue it's because of you know the you didn't write the input okay to buffer the 12 volt keep it stable to the BRM doubt it so now let's get into kind of like transient okay sure I'm so like what is transient response and like why is it important and so like I we were talking earlier right like this this is very simple sorry P equals it goes be VI right this is just power as both there's times current right is fairly easy to understand so what happens like you know when you're when you're providing power over to the CPU right as soon as the CPU kind of hits a high loader it's that's drawing more current right and so you got the current sense over here oh all right so the current sense has to come back to the PW has a feedback information to the PWM controller before the PWM and controller can start saying okay I need to give this I need to provide more current right so if you can imagine right if for example we're giving maybe like we're giving like maybe like 50 watts of power right if your current is starting to spike up you know it goes off from like you know 40 amps to like you know 100 amps right yeah well if you're talking about like 50 watts of power distributed between these two numbers right this is like this is gonna be like 0.2 volts this is gonna be all I just a really bad number um but you know much bigger than it's gonna be should we calculate it yeah we could all right so we we're gonna cut ahead a bit so that we can save some time I'm just plotting that it grabs and everything okay so so what are we looking at right now so right now you know this is the V tour this is the current and it's plotted against time right and so we have to pin it you have like V 2 and V 1 right here these dotted lines they represent a grid okay all right they represent like young this is at the same point so I say old Asian right same time on this and the scale on each one okay and so what happens is when you know your current kind of spikes up right mmm ideal world you'd be at the cutting your voltage of you at the drop and then basically stabilized right away to level out yeah well kind of match up the numbers have to align up right and so when you're when you're reacting over here it comes what actually ends up happening it usually there's a little bit of a because there's a lag time before when the people in control that can react to these so I guess ideally in a perfect world where you have no constraints you know basically a kind of square wave yep or it just it squares out at the edges on each of them but in reality you're you're on is this yes under shoot a different thing is that is it correct use the phrase under shoot for this or now uh or is that a different tactical term undershoot understand fun things you the term mom you guys long block yeah technically that's a different thing no that's that's correct okay but then you're getting into a lot of different ok well let's let's go back what you're saying that um so the we forego that for now um so let me brown these out okay so that you know so this is more of the this is more value what really happens but you know it at the same time frame kind of still flies here right so this will this will kind of dip right and then basically what happens what's happening over here right is because of you know P equals bi right the currents increasing right and the video the few moon control still taking time to react huh so the way you tune it is you start replenishing current at this point and the will make happen is in my kind of in my kind of increase over I say your party of v1 and then maybe under a little bit and then and then stabilized takes it a little bit to fit to to level out to where it needs to be right and what what's happening over here is this duration right you want this to kind of stabilize quickly and you have to make sure this this first peak is not it's not too low not too extreme yeah okay and so what is v1 and v2 you might be kind of like asking is like why does why does the voltage you can change right well if you're if you remember right you have what's called a DC load line uh-huh yeah right and that is the load line looks something like this so basically you know I took her and is going up right this is this this drop to this drop up here that's your low like taking effect okay and this is why I'm getting the load line is because like a lot of people control concerned about the electrical performance because they want the best overclocking capability right and a lot of people will think that like a zero low line is usually like the ideal scenario but what happens when you have a zero low line is you're basically forcing the voltage to try to stay at like v2 all the time okay and so what will happen is you know if you don't have a an appropriately steep low line right mm-hmm this reaction right here will increase as low line gets flatter okay so if you had like a low line let me if we're done with this let me yeah sure clean this real plank so if we so if we applied this over here this is this will basically look like this right b1 and they wanted me to okay this is basically working at I won this is a tie to and then if you have a shallower low line or if you have like a really flat low line right basically I won this will be this will be kind of the one prior asset okay and then e2 would price they'd say so basically it looked like I say basically this this will be like much bigger okay and then the selling time would be actually much long with a shallower load line yeah and so that's like that's why you would need maybe like that's why you need to kind of play around with you know your arms a lot right um I mean I think there is some truth to having a shallow line because I mean in general if the report is tuned very well right for the CPU characteristics I think you can get you can general get away with the shallower load line where you can because it can react properly and kind of dampen you know some of the ball to stabilize either stabilize the current quickly enough right but get like a perfectly flat load line for any CRM is actually extremely difficult order line I think um so that's kind of a quick primer on transient response with a little bit kind of scuffle around a little bit of my little story yeah okay part of the ladder that later date up right the importance of that is just that you know when you're talking about transient response like the magnitude of the the V min right that's like at like something like 50 millivolts right but then your ripple the difference between the two ripple is like something within 5 millivolts right right so it's like a magnitude greater you know of an issue than ripple even though ripple is something that you see may maybe constantly right but because you know as we said like the difference in CPU characteristics now because of the piece CJ yeah cuz of power saving the turbo boosts turbo booster then just having more chorus right having that dynamic current swing right it really changed our priorities yeah you know this is current prophecy yeah I mean if you remember we were stuck at four cores for like years yeah and not just that though if you think about like just like like something like three years ago x99 yeah but the King of Kings was the ten core you know recommendation process right now we're at eight cores on you know on top it's like we're kind of like baffled you know also everybody's like oh oh yeah I think he's selling a portable game well like we want more performance right and I guess this is what can be done at yeah point right now that's seems to be the trend of what's going on yeah oh we're just kind of going with the flow right you have to adjust the designs to match it yeah and so you know there's merits to everything you know everything's you know nothing's perfect right there's trade-offs you're always gonna have to make well you have time and cost - yeah time and money is the ultimate decider on just about everything so yeah yeah cool well I guess that'll give you a brief run-through of some basics from vrm basics so we'll we'll throw to potentially build Zoid video in the future with further discussion on all the stuff here today and thank you for joining me thank you we'll see you all next time