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.
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Our modified values with this frequency are: This means that in gain it acts like a zero, but in phase it acts like a dztasheet. So, in fact, this converter with the components so far needs no compensation network, and we can leave the COMP pin unconnected.
I chose a standard resistor of 0. We’ll find out in the next project log. Can this thing dataeheet fast enough? Here’s the one for the boost converter:.
The converter is a feedback loop, and such feedback loops need to be stable, otherwise your power supply might fail at certain frequencies. Adafruit has a nice boost converter calculatorassuming you’re using the simple single-inductor version. And now for the complex pole. It can handle currents up to 9A, and has an on-resistance of 0. The datasheet doesn’t state this, but ideally the gain margin should be somewhere between 6 and 12 dB.
We must now change both the sense resistor and the slope compensation resistor so that the current limit is sane and the slope compensation resistor is datasheeet the minimum. Datawheet problem is, without knowing control theory, it will be difficult to select the compensation components.
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Again, this is from the Adafruit calculator, but here is the formula: Well actually there is no conclusion until I actually get the parts in to build this thing. Now that we have our pole and zero frequencies, we datashewt to know what the DC gain is. And so I get a sense resistor of 0. Here we see the gain margin is 3.
But, of course, this will not be the case. This gives me a required inductance of at least You want something big with low ESR. I’ll keep using kHz in the calculations as it doesn’t matter much. If Q were infinite, the thing would vibrate itself to pieces and catch fire at half the switching frequency. Maybe start with this list of videos?
Next, we locate the simple pole as follows: 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.
Compute the maximum current flowing through the inductor. The LM datasheet provides a nice series of design procedures for various converter topologies. I hate low-frequency converters with their whining. Here’s the one for the boost converter: Current sense resistors One of these is the resistor that goes between the switch and ground. Sign up Already a member?
Also a duty cycle switch on-time to total time of 0. Maximum inductor current Compute the maximum current flowing through the inductor. One of these is the resistor that goes between the switch and ground. This means raising the frequency or the inductance by at least a factor of 3. They are there to add stability to the converter. The pole is caused by the output capacitor with the load, and the complex pole is caused by the switching action.
And indeed it is. Again, Adafruit gives this as 4. So, let’s take a look at the application note to see what the transfer function looks like without this compensation. Then I started reading about the compensation circuit and realized that I don’t have the means to calculate it. Design procedure The LM datasheet provides a nice series of design procedures for various converter topologies. So with a maximum input voltage of 12V, and an output current of 0.