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힌트: 여러 단어는 쉼표로 구분
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힌트: 여러 단어는 쉼표로 구분
Date
예: 08/09/2022
Date
예: 08/09/2022
Global
China (简体中文)
Japan (日本語)
Korea (한국어)
Taiwan (繁體中文)
TI Training home
Error sources
Output swing
Error sources
이메일
Output swing
[MUSIC PLAYING] Hello, and welcome to the TI Precision Lab series on current sense amplifiers. My name is Kyle Stone, and I am a product marketing engineer in the current and position sensing product line. In this video, we will take a closer look at output swing limitations. Output swing is a common electrical specification found in the data sheet of a typical current sense amplifier, or CSA, for short. There are usually two parameters listed to describe a device's swing to rail characteristics. The first is swing to power supply or swing to the Vs, and the second is swing to ground. These specifications are found in the electrical characteristics table. Often, output swing verse output current is provided in the form of a set of curves in the typical characteristics section of the datasheet. More information can be derived from this graph, such as current capability of the output stage, and its behavior over temperature. In addition to common output swing parameters shown in the previous slide, the INA 190 data sheet also provides a parameter called zero current output voltage and its spec Table The parameter is identical to swing to ground, except that the input differential overdrive is set to zero millivolts. In other words, there is no input over drive. The INA 190 datasheet also provides two plots of the output swing versus output current. These are for two different supply voltages, respectively. Sometimes, all of these curves can be combined into a single plot if it is practical to do so. These are some of the different formats in presenting a device's output swing specifications. Output swing defines how close the current sense amplifier output can be driven to either power supply or ground under specified operating conditions. This relationship is easily demonstrated with an input output curve. Such relationship is shown for a unidirectional CSA and a bidirectional CSA. Ideally, the CSA output should only be limited by ground and the power supply. In between these extremes, the output should vary linearly with input. In other words, the entire range of ground to Vs should be usable and linear. The black line shows this desired behavior. An actual CSA output typically has an output that is slightly below Vs and slightly above ground. In between is a linear section with curved edges as the red line shows. It is exaggerated in order to show the swing limits. In order for a CSA output to be able to support a certain input range, the following set of equations must be true. One, Vn minimum minus Vos times gain is greater than swing to ground. And two, the Vn max plus Vos multiplied by gain is less than swing to Vs. The Vos term in these equations can be omitted if they are much smaller compared to the input voltage terms. The datasheet may not explicitly say it, but we always make sure the output is within the range of swing. Otherwise, the calculation and design may not be valid. More on this later with an example. It should also be noted that the swing to Vs and swing to ground are normally obtained with some input overdrive. Therefore, the range of swing includes both linear output region and nonlinear region. It is a good idea to refer to other parameters for linear output range. For example, in this data sheet, the gain error spec tells us the output is guaranteed to be linear in the range of 100 millivolts above ground, and 100 millivolts below Vs. Let's look at an example how to quickly select the right current sense amplifier by applying the swing to rails as a criterion. In this example, we have Vs equals 5 volts, gain equals 50. The min and max input voltages are 0.5 million volts and 95 millivolts, respectively. We want to see if the INA 282 can work from the perspective of output swing. From the data sheet, we calculate the swing range to be 40 million volts to 4.6 volts. Using the min and max output equations from the previous slide, we get the required lowest output voltage level is below the swing to ground spec, and the required highest output voltage level is above the swing to Vs spec. Therefore, in this example, both swing specs will be violated. We can draw the conclusion that the INA 282 will not satisfy this swing requirement of this application. How do we make it work? There are two possible ways to this approach. First, you can adjust the requirement and measurement range. Second, you can select a different device with a better swing to rail spec. Let's take a look at the same example we looked at previously but substitute with a device that has an improved swing to rail specification, the INA 190. Everything being equal, the only difference is the swing to rail specification. As you can see, in this case, both swing test equations are true with sufficient headroom. The takeaway from this example is that, in general, a device with a wider output swing can accommodate a wider input voltage range. We next look at an overcurrent protection design with the INA 303. In this example, we wish to set the limit resistor for a given current threshold. In the INA 303 datasheet, the equation is provided and the calculation is straightforward. Substituting the numbers into the equation, we can see that the resulting limit resistor value is 75 kiloohms. However, if this design is implemented, it will not work, because the output at the desired trip level is beyond the power supply. The point to note is that we must check to make sure output is within the swing specification at all times, and remember, this is a necessary condition in order for the circuit to function correctly. Let's take a minute to summarize what we learned in this video. One, swing to rail defines how close the current sense amplifier output can be driven to either the power supply or ground under specified operating conditions. Two device output must fall within swing to rail specifications at all times. It is a necessary condition in order for the circuit to function correctly. Three, even though the swing range does not equal to the linear output range, the wider swing range generally means wider linear range. That concludes this video. Thank you for watching. Please try the quiz to check your understanding of the content. For more information and videos on current sense amplifiers, please visit ti.com/currentsense.
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다음
설명
2020년 3월 13일
Learn more about output swing limitations and how to minimize their effects in a current sensing application.
Download webinar slides
current-sense-amplifiers-output-swing-presentation-quiz.pdf
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09:58
1
Introduction to different error sources
08:12
2
Offset error
12:21
3
Gain error
10:35
4
Common-mode rejection ratio
11:47
5
Temperature error
05:16
6
Power supply rejection error
05:39
7
Shunt resistor tolerance error
09:48
8
Output swing
17:10
9
Input filter error
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