WEBVTT NOTE This file was exported by MacCaption version 7.0.13 to comply with the WebVTT specification dated March 27, 2017. 00:00:01.034 --> 00:00:03.770 align:center line:-1 position:50% size:47% Continuing from the previous slide, 00:00:03.770 --> 00:00:09.176 align:center line:-1 position:50% size:44% I have chosen two key features that are commonly looked out for 00:00:09.176 --> 00:00:14.248 align:center line:-1 position:50% size:32% in the DC-DC converter in our session. 00:00:14.248 --> 00:00:16.583 align:center line:-1 position:50% size:48% There are more than just these two. 00:00:16.583 --> 00:00:20.854 align:center line:-1 position:50% size:41% Some datasheets may consist of hundreds of pages 00:00:20.854 --> 00:00:24.324 align:center line:-1 position:50% size:53% highlighting features and specifications. 00:00:24.324 --> 00:00:26.526 align:center line:-1 position:50% size:33% Let's focus on these two. 00:00:31.298 --> 00:00:36.970 align:center line:-1 position:50% size:52% The first feature is high-output stability. 00:00:36.970 --> 00:00:41.541 align:center line:-1 position:50% size:49% The other is low-power consumption. 00:00:41.541 --> 00:00:46.647 align:center line:-1 position:50% size:44% How does one validate that these two features are met? 00:00:46.647 --> 00:00:49.149 align:center line:-1 position:50% size:27% In an ideal situation, 00:00:49.149 --> 00:00:52.653 align:center line:-1 position:50% size:26% the expectation for high output stability 00:00:52.653 --> 00:00:58.892 align:center line:-1 position:50% size:42% is that the output voltage (Vout) should always be constant. 00:00:58.892 --> 00:01:03.297 align:center line:-1 position:50% size:32% In reality, we all know that this is not the case. 00:01:03.297 --> 00:01:07.100 align:center line:-1 position:50% size:36% There are too many factors and considerations 00:01:07.100 --> 00:01:09.937 align:center line:-1 position:50% size:49% that would impact the output voltage. 00:01:12.205 --> 00:01:17.077 align:center line:-1 position:50% size:36% This reduces the variables in the design, 00:01:17.077 --> 00:01:24.451 align:center line:-1 position:50% size:60% but we must at least be certain that the output of the DC-DC converter is reliable 00:01:24.451 --> 00:01:29.089 align:center line:-1 position:50% size:35% to prevent malfunction or degraded performance. 00:01:29.089 --> 00:01:36.063 align:center line:-1 position:50% size:53% The key characteristic to look for for high-output stability in the datasheet 00:01:36.063 --> 00:01:42.569 align:center line:-1 position:50% size:47% is the load and line regulation as well as load transient response. 00:01:42.569 --> 00:01:44.271 align:center line:-1 position:50% size:26% On the other hand, 00:01:44.271 --> 00:01:48.241 align:center line:-1 position:50% size:34% we also need to ensure that the DC-DC converter 00:01:48.241 --> 00:01:53.413 align:center line:-1 position:50% size:58% doesn't always draw power from the source when it is not operating. 00:01:53.413 --> 00:01:57.517 align:center line:-1 position:50% size:47% One might think that when a device is put to sleep or standby, 00:01:57.517 --> 00:02:00.854 align:center line:-1 position:50% size:35% it will not consume power. 00:02:00.854 --> 00:02:03.523 align:center line:-1 position:50% size:20% In fact, it does, 00:02:03.523 --> 00:02:07.694 align:center line:-1 position:50% size:42% thus leading it to waste energy. 00:02:08.829 --> 00:02:11.732 align:center line:-1 position:50% size:34% While we know that a small amount of current 00:02:11.732 --> 00:02:16.403 align:center line:-1 position:50% size:32% would be consumed during sleep or standby, 00:02:16.403 --> 00:02:22.142 align:center line:-1 position:50% size:48% does the designer have to measure such low current? 00:02:22.142 --> 00:02:26.079 align:center line:-1 position:50% size:42% Do they have the means to perform such measurements? 00:02:26.079 --> 00:02:33.487 align:center line:-1 position:50% size:49% The possibility of the low current would range in terms of micro, nano, 00:02:33.487 --> 00:02:37.791 align:center line:-1 position:50% size:36% and sometimes all the way to pico and femto amp. 00:02:37.791 --> 00:02:44.865 align:center line:-1 position:50% size:52% This is where the conversion efficiency and quiescent current are spelled out. 00:02:44.865 --> 00:02:48.835 align:center line:-1 position:50% size:36% Let's look into more details of these characteristics 00:02:48.835 --> 00:02:51.138 align:center line:-1 position:50% size:31% and how it is validated. 00:02:54.741 --> 00:02:58.345 align:center line:-1 position:50% size:41% We'll start with load regulation. 00:02:58.345 --> 00:03:05.919 align:center line:-1 position:50% size:42% What it focuses on is the ability to maintain output stability 00:03:05.919 --> 00:03:08.822 align:center line:-1 position:50% size:42% despite the change of the load. 00:03:08.822 --> 00:03:14.494 align:center line:-1 position:50% size:55% The load change can happen throughout the entire operation of a device. 00:03:14.494 --> 00:03:19.433 align:center line:-1 position:50% size:50% Let's take a smartwatch, for example. 00:03:19.433 --> 00:03:25.806 align:center line:-1 position:50% size:40% When the screen is turned on and showing the time, 00:03:25.806 --> 00:03:30.043 align:center line:-1 position:50% size:31% it is probably operating at an optimum state. 00:03:30.043 --> 00:03:35.082 align:center line:-1 position:50% size:32% But as soon as it is set to measure a heartbeat 00:03:35.082 --> 00:03:38.318 align:center line:-1 position:50% size:30% or blood oxygen level, 00:03:38.318 --> 00:03:43.623 align:center line:-1 position:50% size:34% it is probably operating at its highest load condition. 00:03:43.623 --> 00:03:48.862 align:center line:-1 position:50% size:46% The ability of the DC-DC converter to maintain the output voltage 00:03:48.862 --> 00:03:51.765 align:center line:-1 position:50% size:43% regardless of the change in load 00:03:51.765 --> 00:03:56.436 align:center line:-1 position:50% size:44% is how load regulation is defined. 00:03:56.436 --> 00:03:59.406 align:center line:-1 position:50% size:45% A typical method of performing such measurements 00:03:59.406 --> 00:04:04.678 align:center line:-1 position:50% size:38% is to use a DC power source to provide a constant source 00:04:04.678 --> 00:04:08.849 align:center line:-1 position:50% size:32% while an electronic load emulates the use case 00:04:08.849 --> 00:04:11.818 align:center line:-1 position:50% size:36% of what I've just described. 00:04:11.818 --> 00:04:17.958 align:center line:-1 position:50% size:41% This graph depicts actual data taken from the output voltage 00:04:17.958 --> 00:04:23.296 align:center line:-1 position:50% size:31% that is able to maintain within ± 1%, 00:04:23.296 --> 00:04:26.199 align:center line:-1 position:50% size:47% despite the change of load current, 00:04:26.199 --> 00:04:28.101 align:center line:-1 position:50% size:28% which is really good. 00:04:34.474 --> 00:04:37.144 align:center line:-1 position:50% size:46% Line regulation, on the other hand, 00:04:37.144 --> 00:04:43.283 align:center line:-1 position:50% size:37% focuses on the input portion of the DC-DC converter. 00:04:43.283 --> 00:04:48.688 align:center line:-1 position:50% size:46% As battery levels would deteriorate over a period of usage, 00:04:48.688 --> 00:04:54.494 align:center line:-1 position:50% size:57% the characteristic of line regulation determines how well the DC-DC converter 00:04:54.494 --> 00:05:03.170 align:center line:-1 position:50% size:56% is able to maintain a stable output voltage despite the change in input. 00:05:03.170 --> 00:05:09.876 align:center line:-1 position:50% size:47% Similarly, a DC power source and electronic load would be used. 00:05:09.876 --> 00:05:11.845 align:center line:-1 position:50% size:31% Referring to the graph, 00:05:11.845 --> 00:05:16.082 align:center line:-1 position:50% size:47% what you see here is that despite the change of input voltage 00:05:16.082 --> 00:05:19.719 align:center line:-1 position:50% size:23% from 8 V to 12 V, 00:05:19.719 --> 00:05:24.991 align:center line:-1 position:50% size:43% the output voltage is maintained in the 3.3 V range. 00:05:27.827 --> 00:05:32.666 align:center line:-1 position:50% size:41% The third characteristic that is critical to output stability 00:05:32.666 --> 00:05:35.902 align:center line:-1 position:50% size:41% is the load transient response. 00:05:35.902 --> 00:05:39.606 align:center line:-1 position:50% size:41% This is measured against time. 00:05:39.606 --> 00:05:45.145 align:center line:-1 position:50% size:37% A good example to explain is a sudden change of load, 00:05:45.145 --> 00:05:48.848 align:center line:-1 position:50% size:40% thus creating a surge current. 00:05:48.848 --> 00:05:54.721 align:center line:-1 position:50% size:50% The DC-DC converter will have to recognize that change immediately 00:05:54.721 --> 00:05:58.892 align:center line:-1 position:50% size:56% and recover the voltage and current state. 00:05:58.892 --> 00:06:06.999 align:center line:-1 position:50% size:62% The speed of the DC-DC converter to recover is defined as the load transient response time. 00:06:06.999 --> 00:06:09.436 align:center line:-1 position:50% size:31% Referring to the graph, 00:06:09.436 --> 00:06:15.809 align:center line:-1 position:50% size:38% the output current increases from 5 mA to 500 mA. 00:06:15.809 --> 00:06:18.144 align:center line:-1 position:50% size:34% During the same interval, 00:06:18.144 --> 00:06:22.882 align:center line:-1 position:50% size:39% the voltage level dipped for a couple of microseconds 00:06:22.882 --> 00:06:28.455 align:center line:-1 position:50% size:51% before stabilizing within the tolerance. 00:06:28.455 --> 00:06:30.290 align:center line:-1 position:50% size:26% On the other hand, 00:06:30.290 --> 00:06:34.494 align:center line:-1 position:50% size:50% when the current dropped from 5 mA, 00:06:34.494 --> 00:06:39.799 align:center line:-1 position:50% size:32% the voltage would surge before stabilizing. 00:06:39.799 --> 00:06:44.938 align:center line:-1 position:50% size:36% The load transient is really the amount of time taken 00:06:44.938 --> 00:06:48.008 align:center line:-1 position:50% size:41% for the output state to stabilize. 00:06:48.008 --> 00:06:52.112 align:center line:-1 position:50% size:42% Typically, a designer would use a power source, 00:06:52.112 --> 00:06:55.982 align:center line:-1 position:50% size:30% an electronic load with a pulse capability, 00:06:55.982 --> 00:07:00.153 align:center line:-1 position:50% size:34% and also, an oscilloscope to measure across time. 00:07:05.992 --> 00:07:11.364 align:center line:-1 position:50% size:45% Moving to the second key feature of a DC-DC converter, 00:07:11.364 --> 00:07:14.267 align:center line:-1 position:50% size:19% is efficiency. 00:07:14.267 --> 00:07:17.437 align:center line:-1 position:50% size:35% The word speaks by itself. 00:07:17.437 --> 00:07:25.111 align:center line:-1 position:50% size:48% We want our devices to be as efficient and as lean as possible. 00:07:25.111 --> 00:07:27.914 align:center line:-1 position:50% size:38% Nothing should go to waste. 00:07:27.914 --> 00:07:30.483 align:center line:-1 position:50% size:40% You will know that your circuit is not efficient 00:07:30.483 --> 00:07:33.486 align:center line:-1 position:50% size:33% when heat is generated. 00:07:33.486 --> 00:07:35.322 align:center line:-1 position:50% size:29% As much as possible, 00:07:35.322 --> 00:07:40.493 align:center line:-1 position:50% size:41% we want to keep the efficiency close to 99%. 00:07:40.493 --> 00:07:45.699 align:center line:-1 position:50% size:42% However, this is rarely the case in the real world. 00:07:45.699 --> 00:07:47.500 align:center line:-1 position:50% size:24% In this case study, 00:07:47.500 --> 00:07:54.974 align:center line:-1 position:50% size:42% the DC-DC converter efficiency ranges from 75% to 86%, 00:07:54.974 --> 00:08:00.347 align:center line:-1 position:50% size:39% depending on the load and input voltage conditions. 00:08:00.347 --> 00:08:04.918 align:center line:-1 position:50% size:31% This graph tells us that the lower the voltage, 00:08:04.918 --> 00:08:08.221 align:center line:-1 position:50% size:30% the more efficient it is. 00:08:08.221 --> 00:08:10.323 align:center line:-1 position:50% size:35% Based on this information, 00:08:10.323 --> 00:08:16.529 align:center line:-1 position:50% size:54% the designer can make the right decision to design accordingly. 00:08:16.529 --> 00:08:18.531 align:center line:-1 position:50% size:40% To perform this measurement, 00:08:18.531 --> 00:08:22.702 align:center line:-1 position:50% size:51% on top of the power supply and e load, 00:08:22.702 --> 00:08:25.705 align:center line:-1 position:50% size:43% a current meter is also required, 00:08:25.705 --> 00:08:28.641 align:center line:-1 position:50% size:50% as there is a need to measure power. 00:08:32.612 --> 00:08:37.917 align:center line:-1 position:50% size:51% Last, but not least, is quiescent current. 00:08:37.917 --> 00:08:42.455 align:center line:-1 position:50% size:35% It is the amount of current that a DC-DC converter 00:08:42.455 --> 00:08:46.993 align:center line:-1 position:50% size:38% would draw from the battery or power source 00:08:46.993 --> 00:08:50.397 align:center line:-1 position:50% size:47% when it is operating in sleep mode. 00:08:52.098 --> 00:08:57.904 align:center line:-1 position:50% size:45% You would be surprised at some really poorly designed converters. 00:08:57.904 --> 00:09:00.774 align:center line:-1 position:50% size:37% Have you ever encountered a situation where 00:09:00.774 --> 00:09:05.011 align:center line:-1 position:50% size:39% the battery of your device would be completely drained 00:09:05.011 --> 00:09:08.081 align:center line:-1 position:50% size:49% even though you didn't put it to use? 00:09:08.081 --> 00:09:09.816 align:center line:-1 position:50% size:25% I'm sure you have. 00:09:09.816 --> 00:09:12.452 align:center line:-1 position:50% size:32% If you look at this graph, 00:09:12.452 --> 00:09:17.657 align:center line:-1 position:50% size:39% the input current and voltage still show a significant value, 00:09:17.657 --> 00:09:21.194 align:center line:-1 position:50% size:35% despite the output current being set to 0. 00:09:23.596 --> 00:09:30.537 align:center line:-1 position:50% size:55% A really good DC-DC converter would keep this value as low as possible. 00:09:30.537 --> 00:09:32.505 align:center line:-1 position:50% size:21% To validate this, 00:09:32.505 --> 00:09:35.875 align:center line:-1 position:50% size:52% on top of the power source and e load, 00:09:35.875 --> 00:09:40.046 align:center line:-1 position:50% size:33% you would really need a sensitive current meter 00:09:40.046 --> 00:09:43.783 align:center line:-1 position:50% size:31% that is able to measure really low current. 00:09:47.520 --> 00:09:51.224 align:center line:-1 position:50% size:32% I've just shared with you five key characteristics 00:09:51.224 --> 00:09:57.630 align:center line:-1 position:50% size:39% of a DC-DC converter that often requires validation. 00:09:57.630 --> 00:10:03.102 align:center line:-1 position:50% size:46% You have probably noticed by now that there are certainly challenges 00:10:03.102 --> 00:10:05.839 align:center line:-1 position:50% size:48% to perform all these measurements. 00:10:05.839 --> 00:10:08.441 align:center line:-1 position:50% size:52% Some of the most common challenges 00:10:08.441 --> 00:10:13.012 align:center line:-1 position:50% size:49% are that several different instruments need to be put together 00:10:13.012 --> 00:10:16.082 align:center line:-1 position:50% size:30% to function as a whole. 00:10:16.082 --> 00:10:20.553 align:center line:-1 position:50% size:47% This will be a real problem especially when you are only given 00:10:20.553 --> 00:10:23.756 align:center line:-1 position:50% size:47% a small space in the lab to work on. 00:10:23.756 --> 00:10:27.727 align:center line:-1 position:50% size:40% Space is definitely a concern. 00:10:27.727 --> 00:10:32.298 align:center line:-1 position:50% size:47% It also involves complicated wiring. 00:10:32.298 --> 00:10:38.071 align:center line:-1 position:50% size:54% You need to develop a test program to perform all the instances of validation, 00:10:38.071 --> 00:10:42.141 align:center line:-1 position:50% size:48% not to mention that each instrument has to be synchronized 00:10:42.141 --> 00:10:48.281 align:center line:-1 position:50% size:47% so that the measurement of voltage, current, power, and time 00:10:48.281 --> 00:10:51.618 align:center line:-1 position:50% size:49% is captured at the correct timestamp. 00:10:51.618 --> 00:10:57.457 align:center line:-1 position:50% size:42% I'm sure you have encountered such challenges in your testing.