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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This is fine, since the application note states we want a phase margin between 30 and degrees.
Clearly such a switch has to shut off well before 78ns. Design procedure The Datashet datasheet provides a nice series of design procedures for various converter topologies.
A boost converter design | Details |
Sign up Already a member? Shut up already, datasehet The cause of this is the insanely low maximum sense resistance from above. I’ll keep using kHz in the calculations as it doesn’t matter much. Maybe start with this list of videos?
The converter is a feedback loop, and such feedback loops need to lm34478 stable, otherwise your power supply might fail at certain frequencies. Datasbeet Q were infinite, the thing would vibrate itself to pieces and catch fire at half the switching frequency. The diode has to be able to carry the maximum inductor current. Here’s the one for the boost converter: The LM datasheet provides a nice series of design procedures for various converter topologies.
With that resistor, the current limit would be 5. Again, Adafruit gives this as 4. 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.
It can handle currents up to 9A, and has an on-resistance of 0. The first zero, z1, is caused by the output capacitor with its ESR.
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There are two ways to raise that maximum sense resistance: To power my boost converter, I’d like to use a 12VDC wall adapter. Again, this is from the Adafruit calculator, but here is the formula:. I think I will have to look at other chips such as the LT Compute the minimum inductance required.
About Us Contact Hackaday. Well actually there is no conclusion until I actually get the parts in to build this thing. If not, there are chips specifically designed to drive MOSFET gates at higher currents to force them on and off quickly.
We’ll find out in the next project log. Here’s the one for the boost converter:. However, we now do not need a slope compensation resistor, and everyone is happy. If you don’t know anything about control theory, you probably want to skip this section. Design a boost converter that gives VDC at 0.
LM3478 Datasheet PDF
The datasheet doesn’t state this, but ideally the gain margin should be somewhere between 6 and 12 dB. The problem is, without knowing control theory, it will be difficult to select the compensation components. Nobody datasheett know unless we try it.
Doing that also has a knock-on effect of lowering the inductor current. That is all before you get to the need to plot charts to solve the equations. 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.