Mobile Chip level lecture part 2 (Vbus rail Tracking class)

Added: 2026-06-01

[00:00:00]So hello guys uh you are welcome to easy tech academy you are welcome all right so you're welcome to mobile chip level class so uh this is a lecture that is going on on uh easy tech academy channel okay all right so uh this is our part two class okay whereby in our last class we talk about uh talk about the charging circuit so the term terms that you have to understand.

[00:00:32]So whenever you are working on mobile charging circuit. Okay. All right. So now let's do a revision on our last class. Okay. Let's try to do a little revision. So I'm going to open my my board.

[00:00:52]All right. So now in last class okay I tell you about u three times you have to understand okay that's the three things that I told you in that class okay uh also VPH or B system okay all right so I told you about these three guys. Okay, I told you that this is a 5 volt that is coming from the charger.

[00:01:30]This is a this is a battery this is the voltage that required to charge a battery which is coming from charging IC. So it's in between 3.7 vol to 4.2 two votes and also let this one which is the footage that is going to all mobile section PPH all right so I tell you into details about these three guys okay but now I told you in the last class that uh I'm going to tell you two things that whenever you have anything that related to mobile is not charging okay so you are finding two things. Um let me say basically you are finding two things. Okay. All right. You are finding two guys when a customer come to you and told you that techn as a technician that he or she mobile phone is not charging.

[00:02:38]Okay. So guys in just a brief you are finding two guys. Just have in mind that you are finding two guys. That's the basic that's the basic of finding mobile charging faults. Okay. First you are finding if your fee boss is available.

[00:03:04]If your feed bat is available.

[00:03:08]So that's the two guys you are finding.

[00:03:11]Basically, I repeat, basically that's the two guys you are finding. Okay, you have to check does the this guy is available.

[00:03:22]Does this guy come out?

[00:03:26]Okay, that's the two things basically you are dealing with. Okay. All right.

[00:03:34]So now I'm going to I will go on schematics.

[00:03:39]uh we shall go on schematics and uh we have to learn about that two guys and how to troubleshoot them. Okay.

[00:03:50]So now let me try to open my schematics.

[00:03:55]All right. Okay.

[00:04:01]So all right. So guys uh this is uh infin okay that's x 68 tob so that's what we want to use as a case study all right okay so now I told you that we are dealing with two guys whenever you have a charging fault Okay. So now let me tell you one thing before we move before we proceed.

[00:04:37]All right. Okay.

[00:04:40]See see this guy is another case study.

[00:04:47]Okay. All right.

[00:04:54]So this guy also it's another case case study. Okay, that's another case study. All right.

[00:05:10]But now we are dealing with these two guys Fibos and Fibat.

[00:05:25]So that's the that's the two guys you want to deal with now. Okay. All right.

[00:05:32]Now whenever you have issue on uh mobile is not charging. Okay.

[00:05:38]The first thing you have to check is your fibos. Let's start from fibos you know that this guy is the one that is coming from charot.

[00:05:49]Okay.

[00:05:52]And this guy is the one that will serve as a input.

[00:05:58]So it will ser as a input to charging IC to start work.

[00:06:07]If this guy is not present, if this guy is not present, charging IC cannot activate.

[00:06:16]Okay. The charging IC cannot activate.

[00:06:22]Charging IC need this guy Fibos to start work.

[00:06:28]Whenever foss reach to charging IC just know that the charging IC will horn now it will start a work what is work that charging IC is do so let me just in modern charging IC they have a lot of work that they are doing but let's just talk about the major work that is doing charging IC is like a step down. I see.

[00:06:58]Let me clean this guy.

[00:07:01]It serve as a step down.

[00:07:08]You know when we go into uh whenever you are talking about going to electronics music, you have what we call step up and step down.

[00:07:30]transformer.

[00:07:33]We have step up transformer. We have step down transformer. Okay. All right.

[00:07:38]So now charging IC is like a step down.

[00:07:43]It will step down this F bus which is 5 volt.

[00:07:49]Just have in mind that 5 volt cannot is not a voltage that is required to charge your battery battery. Okay, 5 volt is a voltage that charging IC will manage and subdue to a voltage that is required to charge battery. A voltage that is required to charge battery is from 3.7 volt generally to a mobile phone to 4.2 two volts.

[00:08:19]Any voltage greater than this, any voltage greater than greater than this, just know that your battery will have a problem because that's not require that's not the requirement.

[00:08:41]So if all 5 volt get to the battery to charge the battery.

[00:08:47]So that load is too much for the battery.

[00:08:50]That current is too much is too much for the battery. Okay. All right. So having in the mind that I is stepping stepping down stepping down this guy to the requirement voltage that is able to charge battery. Okay. Now that's the first cases you have to uh you have to study. Okay.

[00:09:17]What are the condition that can happen to this guy whenever you are troubleshooting charging problem? What are the condition?

[00:09:28]Let's check the condition that can happen to this guy whenever you are troubleshooting charging problem. Okay.

[00:09:37]So the different cases that that can happen.

[00:09:40]Okay. So let's go to the board.

[00:09:43]All right. So the first thing is that you know P bus generally is 5 volts.

[00:09:54]There is a possibility that this guy reduce.

[00:10:03]Sometimes you can see like two volts.

[00:10:15]Sometimes you can see even some little current uh current consumption on your multimeter. You just see that you just have some little number even or not up to 5 volts.

[00:10:30]So you just see that on the test bond of P bus this thing is appearing. So it's telling you that the voltage is not enough.

[00:10:43]Okay.

[00:10:44]All right. That's the first cases that usually happen to this guy. So this mean that you have to check if that five 5 volt is average is complete 5 volt which although you can have like sometimes you can have like 4.7 volt can have like 4.9 volt approximately they are still 5 volt so don't be confused but anything less than 5 volt just know that your mobile will not charge and if your mobile charge there some cases that the mobile will charge but but now this is what will happen it depend of it depend on the architecture of the charging cycle there are some architecture that we not allow to charge it whenever if that voltage is not enough so now let's say that for charging IC instead of 5 volt you see like 2 volt that is charging IC Okay. If two volt reach charging IC, if charging IC even step down this voltage, maybe we can have like one voltage.

[00:12:03]Sometimes can have like a even like a little voltage that will go to your battery connector.

[00:12:21]What happens is that when it's either one volt or this voltage get to this battery connector the power IC will sense that the phone is charging that cases you can see that your charging indicate you have the lead indicates the lead, the charging lead indicates that white lead. And in that case, when you change your check your uh mobile phone bar, the charging bar, maybe your phone is at like 65 percentage.

[00:13:03]You know that there's a logo that will behind it that will serve that the phone is charging.

[00:13:09]You see that logo also, but it will not increase.

[00:13:13]it will not increase.

[00:13:16]Why? Because that voltage is not enough.

[00:13:20]And where is the fault is coming from?

[00:13:22]From the fe. Because that feage is not enough. And there are some cases will not it will not even charge at all. It will not even charge. Okay. All right.

[00:13:33]So that's one case. That's the cases about this guy. And there is there is a there are sometimes that V balls can short the 5 volt will be short.

[00:13:55]So if 5 volts short if this 5 volt short zero voltage will go to charging IC phone will not charge at all.

[00:14:07]There are some cases that this fiber will not even appear at all. It will not even come.

[00:14:14]Okay. All right. So now let's go on schematics.

[00:14:23]Now let's try to trace.

[00:14:26]All right. So we all know that let me try to open the subboard.

[00:14:37]So all right. Okay.

[00:14:43]So now this our charging port. This our charging port.

[00:14:48]So this our five pin charging port.

[00:14:51]Okay. Can see that I'm on the leg.

[00:14:55]Okay. So this is the fib bus. So the fib bus is coming from the charging port.

[00:15:01]So after then it will get to the it will pass through this diode on the subboard. Okay. It through this diode it will go to this connector.

[00:15:15]So that's the that's the 5 volt connector.

[00:15:19]Can see this ion.

[00:15:24]So that's the 5 volt where you can check 5 volt this ion. Okay. Can see this where the fibos is coming from. So it's coming to this ion.

[00:15:36]All right. So that's how to track fibos free ray. Okay. That's how to track it.

[00:15:41]That's how to track it. Okay. So now if any problem happen to this guy.

[00:15:53]So just know that you have to trace the fibos ray from the charging port.

[00:15:58]What can cause the issue? Maybe it's not well fixed. Maybe there's a corrosion on it. Okay. Which is not allowing the current to flow. Okay. There is there can be a problem with this diode. This guy. Okay. All right.

[00:16:18]There there can be a problem with this with this guy also. This connector.

[00:16:24]That's how to track.

[00:16:28]Okay. There are sometimes if this ion remove there's no way for that guy to be transferred.

[00:16:36]And you know that from this connector through the flex it will go to the main board.

[00:16:44]Okay.

[00:16:46]So now in order to do finishing for this guy this subboard just come here check your 5 volt here. If your five vol is not coming just know that this subboard have issue.

[00:16:58]Okay. The issue can come from this guy.

[00:17:01]Maybe that diode has short or has any problem or your charger port. This diode or your charger port.

[00:17:12]Okay. But this this is the finishing for the subboard. Just check this connector. Now if we reach this connector what is the next next thing? So you have to trace your fib bus here.

[00:17:28]Okay you have to come uh where is the fibos test point. So this is the fib bus test point. This is the main board. So, so far when you test on this guy if Fibos available here and is accurate 5 volt or you have something like 4 7 volt or you have something like 4.9 volt.

[00:17:58]So approximately is still a 5 volt.

[00:18:03]All right. So now uh this problem usually occurs sometimes that you will have a reduction little reduction like this is because of the diode principle. You know that there's a diode on that subboard. Okay. So if voltage pass through diode sometimes so for that diode to switch it will conduct some little current.

[00:18:33]So that little consumption will make this voltage reduce little bit.

[00:18:39]Okay. But yet if you approximate this it will still give you 5 volt. So take note of that. Okay. So now if your 5 volt has reached this test point just know that your 5 volt has get to the main board. So there's nothing concerning with the subboard or the flex. So the flex also can be the issue.

[00:19:03]Maybe the the the Fibos Ray has has been cut. Okay. All right. So after then if your 5 volt is available here then you are good to go.

[00:19:14]What next? Your 5 volt is going to this guy.

[00:19:21]This is Fibos capacitor which is an input capacitor to OBP IC.

[00:19:31]If there is a problem with this capacitor, maybe this capacitor has been damaged short, you know that your 5 volt will not get to this OBP IC.

[00:19:42]And if this 5 volt doesn't get to the OBPC, your 5 volt will not get to the charging IC. So, it will not charge. That's how to trace a charging port. Okay? And now if there is a problem with your OVP IC sometimes this OB IC can short can short okay so we have different type of OBP IC there are some OBIC that can be that can be bypassed that there are OBIC that cannot be not be bypassed Okay. So in that case you have to find another OBIC of the same type in replacement.

[00:20:34]Okay. All right. So that's another class. Okay. Um we have something we call analog IC.

[00:20:47]IC and digital IC.

[00:20:55]Analog IC can be bypassed but digital IC cannot be bypassed. So that's another class. Okay. So let's continue. So now I have told you the work of OBP in the last class that is uh is a security that is measuring the guys called BOS.

[00:21:15]Okay. So I told you deeply on uh in last class that uh about the OBP work. So now let's continue. So after the OBP have tested the P bus and it pass through the examination of OBBIC then OBBIC will it will release the 5 volt.

[00:21:38]Okay. It will release the 5 volts. You can see know that in like in in last class I told you that when a signal is passing through different process the name will change or have attachment you can see that the V bus see the V the the V bus OVP voltage is different from ordinary VOS.

[00:22:06]This is what you have to understand whenever you are dealing with schematics.

[00:22:10]This is not ordinary feb that is now giving out this feed bus.

[00:22:17]It's not this feed bus is no longer a fe that is coming from your charger. Again this signal is telling you that this feed bus is the one that OBP has tested and tell the IC that this guy is good is good for you to use. So this guy is different from the OVP. That's why we have Fibos OVB.

[00:22:39]Okay. So I have told you in that last class that when signal is passing passing through um some process the name will change.

[00:22:49]Hope you get it guys. Okay. All right.

[00:22:53]So now this is going directly to the charging IC but not directly there must be an input capacitor.

[00:23:06]All right. So this is the input capacitor to the charging IC Fibos OVP. Now through this capacitor.

[00:23:21]Okay. Sorry. This is a coil.

[00:23:24]This is a coil. And not withstand the this is the this is the input capacitor.

[00:23:32]Okay. So if this guy if this guy has a fault, your phone will not charge. If this guy has a port because that's the fib right it will not charge. So now the when whenever you are troubleshooting whenever you are troubleshooting charging problem. So the first way to confirm your P bus that it is present totally present is this input capacitor.

[00:24:07]So when you put your multimeter probe on this guy and you see that you have 5 volts then f have been confirmed and good to go.

[00:24:18]So there's no need of checking this guy and you see that the voltage is accurate and not fluating. It's not going up and down. There's no it's not flunating. You see that everything is perfect is it maintain the standard of 5 volts. Okay.

[00:24:33]All right. So you know that the cases on 5 volt fibos line fib has been solved.

[00:24:41]Okay that's the perfect that's the perfect uh point to test. Okay you know that this charging IC is a ball is a ball charging IC. So you can't test the leg until you remove it. So that's the that's the it's either you test from this guy or from this guy for the input of the fib bus to the charging IC. Okay. So guys guys so now I hope you understand.

[00:25:16]So this is how to track this how to troubleshoot.

[00:25:20]Okay, you can see that uh with all this news that uh I am reading to you guys since uh maybe some minute ago now we are still talking about 5 volt tracking r so whenever when I told you that we are finding two guys you just take in your mind that uh it's just this these two guys that we are now finding in charging I you can see that there is many thing that comprises on on the road on the road of fibos ray. Okay, that can make phone that can make phone not to charge.

[00:25:56]So you see that that fibos is not ordinary foss is there are something comprises inside it. Okay. All right. So let's stop there. Let's stop here guys.

[00:26:08]So we are going to track febat footage in the next class. So let me see your comment. Let me see your comment. So let me see your comment and remember if you are new to this account remember to subscribe okay and click on like button okay. All right so guys I will meet you in the next class. Bye for now.