switching frequency of LM can be adjusted to any value between kHz and .. mode. All the analysis in this datasheet assumes operation in continuous . Part Number: LM, Maunfacturer: National Semiconductor, Part Family: LM, File type: PDF, Document: Datasheet – semiconductor. Datasheets, LM Design Resources, LM Design with WEBENCH® Power Designer. Featured Product, Create your power design now with TI’s.
|Published (Last):||20 January 2015|
|PDF File Size:||7.53 Mb|
|ePub File Size:||6.87 Mb|
|Price:||Free* [*Free Regsitration Required]|
I think I will have to look at lm3487 chips such as the LT Thus, instead of a maximum sense resistance of 0. We see that there are two zeros, one pole, and one complex pole: Maximum inductor current Compute the maximum current flowing through the inductor. Min and max output voltage are VDC, output current is 0.
LM overview, product comparison and replacement search
I’ll keep using kHz in the calculations as it doesn’t matter much. We got this from the Adafruit calculator, 0. You can see the resonance at half the switching frequency. So this is really a good thing. Can this thing switch fast enough?
A boost converter design | Details |
Here we see the gain margin is 3. This means that in gain it acts like a zero, but in phase it acts like a pole. We can see that unity gain occurs at 2. However, we now do not need a slope compensation resistor, and everyone is happy. Current sense resistors One of these is the resistor that goes between the switch and ground.
So with a maximum input voltage of 12V, and an output current of 0.
There is a second resistor which goes between the current sense pin of the converter and the current sense resistor. Maybe start with this list of videos? The first zero, z1, is datasheet by the output capacitor with its ESR. We first calculate the maximum sense resistor for current mode loop stability loop stability is always a good thing: Note that the Adafruit calculator correctly, in my opinion uses the lowest of two possible duty cycle based on the minimum input and output voltage, because this will result in the highest minimum inductance.
The problem is, without knowing control theory, it will be difficult to select the compensation components.
We need to find Q, which is the damping factor. Design a boost converter that gives VDC at 0. Let’s locate the zeros: Output capacitor selection You want something big with low ESR. With that resistor, the current limit would be 5. This is fine, since the application note states we want a phase margin between 30 and degrees. Note that the converter will adjust the duty cycle based on the output voltage and switch current, so this is only a value for calculation.
LM3478 Boost Controller overview
Shut up already, converter! Minimum inductance Compute the minimum inductance required. Anyway, this is a good worked example, and very relevant! If you don’t know anything about control theory, you probably want to skip this section.
I chose kHz because I wanted it to be above the minimum, but not so fast that all my components had to be super-fast. Then I started reading about the compensation circuit and realized that I don’t have the means to calculate it.
This means raising the frequency or the inductance by at least a factor of 3. So, in fact, this converter with the components so far needs no compensation datwsheet, and we can leave the COMP pin unconnected.
I don’t know, but suspect that the output voltage of the adapter will drop under load, so I’m just going to go ahead and specify a minimum input voltage of 8VDC.