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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About Us Contact Hackaday. If not, there are chips specifically designed to drive MOSFET gates at higher currents to force them on and off quickly.

LM3478 Datasheet PDF

So with a maximum input voltage of 12V, and an output current of 0. Clearly such a switch has to shut off well before 78ns. There’s a COMP pin on the converter where you put a resistor and capacitor in series. We can see that unity gain occurs at 2.


A boost converter design | Details |

Sign datashet Already a member? Adafruit has a nice boost converter calculatorassuming you’re using the simple single-inductor version. Compute the maximum current flowing through the inductor. This means raising the frequency or the inductance by at least a factor of 3.

This means that in gain it acts like a zero, but in phase it acts like a pole. That is all before you get to the need to plot charts to solve the equations.


The LM datasheet provides a nice datashewt of design procedures for various converter topologies. Again, this is from the Adafruit calculator, but here is the formula:.

Again, Adafruit correctly is using the D based on the maximum input voltage, but I’m using a higher value for extra safety margin. If Q were infinite, the thing would vibrate itself to pieces and catch fire at half the switching frequency.

The gain margin is minus the gain at which the phase is degrees. Now that we have our pole and zero frequencies, we need to datashwet what the DC gain is.

LM Datasheet(PDF) – National Semiconductor (TI)

Let’s locate the zeros: The new current limit, of course, didn’t change from before because we chose the same sense resistor. And so I get a current of 4. To power my boost converter, I’d like to use a 12VDC wall adapter. Maximum inductor current Compute the maximum current flowing through the inductor. Doing that also has a knock-on effect of lowering the inductor current. One of these is the resistor that goes between the switch and ground.

The second zero, z2, is caused by the inductor and the load on the power supply. The pole is caused by the output capacitor with the load, and the complex pole is caused by the switching action. You can see the resonance at half the switching frequency. It must also be able to withstand a reverse bias of the output voltage minus the input voltage.


So based on the inductance and current, I can choose an inductor that can handle this current. So, let’s take a look at the application note to see what the transfer function looks like without this compensation. Can this thing switch fast enough? Next, compute the duty cycle, D. Yes, delete it Cancel.

I think I will have to look ln3478 other chips such as the LT These margins are important because the poles and zeros shift with varying load and input voltage, and without these margins your circuit could go unstable. This gives me a required inductance of at least I chose a standard resistor of 0. Switching frequency First, choose a switching frequency between kHz and 1MHz. So this is really a good thing. And, lm478 course, this pole is located at half the switching frequency:. Anyway, this is a good worked example, and very relevant!

Datashheet, the margins cannot be too great otherwise the system doesn’t react quickly to changes.