WEBVTT 00:00.920 --> 00:02.240 I have a question for you. 00:02.240 --> 00:07.080 Can you tell me in comment section what is reflection in single high speed net? 00:07.480 --> 00:10.120 Hello people, welcome to stream PCB YouTube channel. 00:10.480 --> 00:13.760 In this video we are going to talk about signal integrity. 00:14.240 --> 00:19.200 For this topic I am referring to Signal Integrity Simplified book by Eric Bogatin. 00:19.360 --> 00:23.000 I guess nothing else is required to understand this topic very better. 00:23.200 --> 00:29.200 So if you wanted to go in very detail, you can click over the link given on the description and follow 00:29.200 --> 00:29.800 this book. 00:30.800 --> 00:37.480 Now before starting this topic, I want to thank EMA EDA for supporting steam PCB and providing all 00:37.480 --> 00:43.440 the learning material which I will be sharing with the world through this YouTube channel so people 00:43.440 --> 00:48.600 you can go to their website and get security CIS simulation tool free trial. 00:48.880 --> 00:54.040 I'll put link in the description because very soon I am going to start simulation part further on this 00:54.040 --> 00:55.000 high speed series. 00:55.880 --> 00:56.120 People. 00:56.120 --> 01:01.280 You can support this channel as well by enrolling into steam, PCB, mixed signal and high speed board 01:01.280 --> 01:02.280 design courses. 01:03.200 --> 01:07.200 With that said, let's move to our topic signal integrity. 01:08.360 --> 01:11.040 Let's start with what is high speed signal. 01:16.160 --> 01:30.280 So the signal which has clock frequency greater than or equal to 100MHz and rise time less than or equal 01:30.280 --> 01:34.240 to one nanoseconds are high speed tracks or high speed signals. 01:36.520 --> 01:40.840 Another question that we can ask what is what is signal integrity? 01:43.080 --> 01:50.960 So signal integrity refers to all the problems arise due to interconnects in any high speed product. 01:51.080 --> 01:53.960 That is what is signal integrity is all right. 01:54.120 --> 02:00.960 So you can say all the problems due to. 02:04.440 --> 02:08.800 Transmission line or interconnects. 02:13.920 --> 02:16.520 In any high speed products. 02:19.080 --> 02:19.680 All right. 02:19.680 --> 02:21.680 So here we used another term. 02:22.200 --> 02:24.520 Transmission line and interconnect. 02:25.400 --> 02:26.840 So let's talk about that. 02:27.000 --> 02:31.000 What are transmission line and interconnects to discuss further. 02:31.920 --> 02:35.800 In transmission line let's suppose we have a transmitter. 02:36.880 --> 02:37.240 All right. 02:37.280 --> 02:39.880 Which kind of generate the signal. 02:40.480 --> 02:43.480 And we have a receiver. 02:43.520 --> 02:44.040 Right. 02:44.360 --> 02:50.600 And between transmitter and receiver we have interconnects. 02:51.040 --> 02:57.720 So when I'm using this term interconnects it refers to everything between transmitter and receiver. 02:57.720 --> 03:09.110 For example it refers to package it referred to tracks in a board or PCB. 03:10.110 --> 03:17.030 It referred to vias that we are using for layer change, and after layer change we are again routing 03:17.030 --> 03:18.630 our tracks on a PCB. 03:21.070 --> 03:31.270 Then again go back to package at the other side, or you can say at the receiver side, and then our 03:31.270 --> 03:32.910 signal will finally receive. 03:33.190 --> 03:39.950 So everything comes between transmitter and receiver is a part of interconnect. 03:40.790 --> 03:41.350 All right. 03:41.470 --> 03:47.390 And whenever interconnects are not properly designed either by the chip manufacturer or by the hardware 03:47.390 --> 03:53.430 designer or PCB designer, then see problems arise. 03:55.550 --> 03:55.870 All right. 03:55.870 --> 03:59.150 So we will discuss that in very detail later. 03:59.550 --> 04:01.750 Let's move to our another point. 04:02.310 --> 04:07.470 So we can divide all type of C problems into three major categories. 04:10.630 --> 04:22.990 So first category is noises, and under noises the C problem comes a a problem is ringing. 04:23.510 --> 04:24.110 All right. 04:24.990 --> 04:26.190 So how ringing looks. 04:26.550 --> 04:28.430 So suppose we have a signal here. 04:28.430 --> 04:32.150 And it just oscillate and then stabilize itself. 04:32.950 --> 04:37.510 So if you are seeing this kind of waveform then this is related to ringing. 04:39.030 --> 04:42.950 We will discuss cause and solution of these problems later. 04:43.310 --> 04:45.390 Another problem can be ground bounce. 04:50.070 --> 04:51.750 So this is our zero volt. 04:53.750 --> 04:58.070 And instead of a constant zero volt on this you will see some spikes. 04:59.190 --> 05:03.150 It can be positive negative or in both direction right. 05:03.230 --> 05:05.110 So this is due to ground bounce. 05:07.070 --> 05:09.150 Another problem can be reflection. 05:13.910 --> 05:15.710 So how reflection waveform looks like. 05:17.510 --> 05:19.790 It will be like something like this. 05:19.950 --> 05:20.430 Right. 05:20.430 --> 05:22.550 So here you can see first reflection here. 05:23.710 --> 05:25.590 Second here like that. 05:27.830 --> 05:29.350 Then another noises. 05:29.350 --> 05:30.350 Problem is. 05:34.830 --> 05:39.710 Near end crosstalk and far end crosstalk. 05:43.830 --> 05:47.390 So here we can take an example how it looks like. 05:50.870 --> 05:52.310 So this is our. 05:54.190 --> 05:57.870 So ideally let's suppose this is our aggressor net. 05:58.790 --> 05:59.310 All right. 05:59.350 --> 06:04.150 So crosstalk means we have a aggressor net and we have a victim net. 06:04.270 --> 06:09.910 So because of some signal is going to transfer on egress on it. 06:09.950 --> 06:13.110 It is causing some spikes on victim minutes. 06:13.310 --> 06:13.790 Right. 06:14.790 --> 06:19.670 So if it is causing a positive spike on victim net then. 06:21.910 --> 06:23.150 Due to this rising. 06:24.510 --> 06:29.910 Okay, that will be our next or near end crosstalk. 06:30.510 --> 06:38.590 And if it is causing negative spike then it will be fixed or far end crosstalk. 06:40.350 --> 06:40.630 All right. 06:40.670 --> 06:42.590 And this is our aggressor net. 06:46.550 --> 06:48.110 Another problem can be. 06:52.070 --> 06:52.950 Switching noise. 07:01.630 --> 07:03.510 So here we have two waveforms. 07:03.910 --> 07:06.660 This is again a kind of crosstalk Talk. 07:06.700 --> 07:07.140 Right. 07:08.020 --> 07:18.420 So one aggressor net it is switching but it is causing some problems in the victim net waveform. 07:18.620 --> 07:19.340 Right. 07:19.380 --> 07:19.580 Right. 07:19.580 --> 07:20.020 This. 07:21.780 --> 07:22.140 Right. 07:22.140 --> 07:23.860 So this is kind of switching noise. 07:24.500 --> 07:30.500 Another problem again comes under noises is load capacitance. 07:35.620 --> 07:40.460 So how load how waveforms looks like for load capacitance case. 07:41.300 --> 07:43.100 So it will be like this. 07:44.180 --> 07:48.780 If you see any these kind of waveform it can be in positive and negative both direction. 07:49.620 --> 07:52.820 Then this is happening due to load capacitance on the line. 07:54.460 --> 07:55.100 All right. 07:55.500 --> 08:05.620 Similarly we can move to another noise problems that can be due to attenuation okay. 08:07.260 --> 08:08.940 So how waveforms looks like. 08:09.180 --> 08:13.700 If there is attenuation in your track due to something. 08:13.980 --> 08:14.260 All right. 08:14.300 --> 08:15.500 We'll discuss that later. 08:16.100 --> 08:19.860 So ideally the waveform should be like this right. 08:20.020 --> 08:32.900 But due to attenuation it couldn't able to reach the full uh you can say uh the full voltage and start 08:32.940 --> 08:33.660 slowing down. 08:37.700 --> 08:38.140 Right. 08:38.180 --> 08:40.220 So these are all the attenuated waveforms. 08:42.100 --> 08:42.540 All right. 08:42.540 --> 08:44.060 So these are some problems. 08:44.060 --> 08:49.220 Similarly you can go for uh you can look for non monotonicity. 08:49.460 --> 08:51.140 That is again a problem. 08:51.140 --> 08:53.940 You can go for power bounds. 08:54.180 --> 08:59.460 So similarly like ground bounce you will see spikes on power lines or power planes. 09:00.460 --> 09:01.100 All right. 09:01.340 --> 09:03.460 So these are all the noise problem. 09:03.500 --> 09:05.220 Let's look for second category. 09:05.540 --> 09:09.300 And second category is EMI and EMC. 09:11.820 --> 09:12.300 Okay. 09:12.340 --> 09:13.460 So I'm just going to tell you. 09:13.500 --> 09:14.460 Definition here. 09:14.580 --> 09:17.820 So EMI is most related to electromagnetic. 09:17.860 --> 09:22.940 Emission from your hardware or chip or tracks. 09:22.980 --> 09:23.180 Okay. 09:23.220 --> 09:27.220 So that is emission from board or from PCB. 09:28.020 --> 09:29.060 Or from product. 09:29.100 --> 09:32.100 You can say anything right now. 09:32.140 --> 09:36.780 EMC is related to compliance right. 09:37.100 --> 09:41.860 So it is effect of emission to your board. 09:42.140 --> 09:46.180 So that means your board is sitting somewhere inside a product. 09:46.540 --> 09:49.820 And we have another part which is causing. 09:50.580 --> 09:52.340 The electromagnetic emission. 09:52.580 --> 09:53.100 Right. 09:53.140 --> 09:56.820 And it is kind of affecting your PCB right. 09:56.900 --> 10:05.460 So your PCB should be protected for both of the cases for emission, for electromagnetic interference 10:05.460 --> 10:10.740 and for electromagnetic It's all right for both of the cases. 10:10.740 --> 10:13.060 Your PCB should be designed like that. 10:14.460 --> 10:15.020 All right. 10:15.180 --> 10:18.420 Let's discuss the third category, which is related to timing. 10:20.820 --> 10:21.220 Okay. 10:21.540 --> 10:26.500 So timing is basically we are talking about clock period. 10:26.780 --> 10:27.140 Okay. 10:27.940 --> 10:29.740 So we have one clock period. 10:30.340 --> 10:30.900 All right. 10:31.740 --> 10:44.940 And we basically allocate that clock period to let's suppose 5 to 10 processes okay. 10:45.220 --> 10:54.420 And due to signal integrity if the if something happened to this timing or this clock period okay. 10:54.460 --> 10:55.580 Either it can be delay. 10:55.580 --> 10:56.740 It can be attenuation. 10:56.740 --> 10:59.100 It can be anything okay. 11:00.020 --> 11:02.660 So it will cause interrupts. 11:02.780 --> 11:08.460 Or you can say halt in these processes right. 11:08.740 --> 11:10.570 Or stop these processes. 11:11.450 --> 11:11.970 Right. 11:12.010 --> 11:14.930 So these are all the problems which comes under. 11:14.970 --> 11:18.690 Under the timing related signal integrity issues. 11:18.850 --> 11:19.010 Okay. 11:19.050 --> 11:21.050 We'll discuss that in more detail later. 11:22.170 --> 11:29.490 If we'll explore more under these three categories, we'll get to know about 25 different problems. 11:29.490 --> 11:33.170 Even more than that different signal integrity problems. 11:33.210 --> 11:33.850 All right. 11:34.010 --> 11:37.250 So we have to understand the root cause of these problems. 11:37.250 --> 11:40.130 And what are the solutions okay. 11:41.650 --> 11:50.970 Another step is now we can further devise divide these 25 or more than that problems into six major 11:51.090 --> 11:55.410 parts that we are going to cover in upcoming videos. 11:55.810 --> 11:59.850 So I hope this video was useful for you and you have learned couple of things. 12:01.010 --> 12:07.170 In case of any doubt, or you have any questions you can put in the comment section, I will reply you 12:07.170 --> 12:08.090 there ASAP. 12:08.690 --> 12:09.090 Thank you. 12:09.130 --> 12:10.370 See you on the next video.