For the “interpretation method of power IC technical specifications”, we have explained “technical specification cover”, “block diagram”, “absolute maximum rated and recommended working conditions”, “key points of electrical characteristics”, “drawing method of characteristic chart and waveform” and “application circuit example”. Next, an example is given to illustrate how to look at the information about “component selection” necessary for design, especially the important “output LC filter” and “phase compensation” in switching regulators.
· component selection
The item “interpretation method of power IC technical specifications: application circuit example” has explained that in addition to circuit examples, some manufacturers or IC sometimes include the list information of component constants such as output voltage according to the set value. This is bound to be very convenient, but if you want to make micro adjustments or use them under conditions other than prompts, it is troublesome to have no suitable components or to calculate constants. Therefore, the technical specifications contain the carrying function or its setting method, the selection method of necessary external components, and the calculation formula for constant determination.
The following is an excerpt from the relevant description of “output LC filter constant” in the “component selection” item of the technical specifications. As far as content is concerned, the content describes what formula should be used to determine what value should be determined when determining the constant of the output LC filter. In fact, there is a further explanation that constants that satisfy the conditions to be set can be calculated.
Here is another example. Although also excerpted from technical specifications, there are methods for calculating the components and constants necessary for the phase compensation circuit of the switching regulator.
It may be a little far fetched, but it should be understood that it is very important for the design to start from the work description and show the calculation formula in detail. If you want to optimize your work or features, you can’t design or adjust them without understanding them in advance.
For example, the resistance value and formula for setting the output voltage are not recorded in such detail. They are basically determined by the calculation formula. It can be thought that the reason is that it is not too difficult to know “why it is like that”. On the contrary, the illustrated output filter or phase compensation can be thought of as not being able to handle if “what’s that” and “why would that be so”. Further, it can be interpreted that those key points bear the brunt of design or adjustment.
Although the content is not easy to understand, but if you do not understand, the power supply can not be completed. Fortunately, the output filter or phase compensation illustrated in this paper is based on the same idea, even if the circuit structure or constant and calculation formula are slightly different depending on the manufacturer or IC type. Although these two points deviate from the theme of this project, it is very helpful to understand the principle in advance for power supply design.
The details of “component selection” depend on the manufacturer or IC, some of which are not technical specifications, and the appellation varies from manufacturer to manufacturer. Sometimes it is attached to application memorandum or design and operation manual. If design is the premise, these should be basically available. In addition, sometimes even if there are some of the above-mentioned instructions and attached books, they can not cover all of them, so we must ask the manufacturer.
The evaluation board is as above, and it is noted here for reference. The model of the evaluation board is recorded in the technical specifications. Sometimes, although there is a URL for reference, there is a link to provide relevant information when visiting the product page of the manufacturer’s home page in recent years. For example, this is the home page of bd9a300muv, with the “download evaluation board data” button. Please take a look at the content after downloading. In addition to the specification of the board, the user manual of the evaluation board also prompts the correction method, substrate layout, etc. In addition, there are also photo files to prompt the layout of the substrate.
The method of selection of components and constant calculation required by prompt design.
The detailed information is sometimes provided with information beyond the technical specifications such as application memorandum.
The relevant records of output LC filter and phase compensation of switching regulator are very important.