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For the input filter, it's important to have the capacitor close to the supply terminal, with a small loop area to GND. This cap supplies the high-side transient.

This would imply C-L-C-L-C input sequence as shown in the MPQ appnote to be preferred.

Layout matters too: minimize the loop areas for both the main input cap and especially the output cap. These have a profound influence on radiated emissions.

Here's a sim to play with (simulate it here):

You can see that the current ripple at the 5V input is pretty well knocked down by the double-pi filter.

But take note of transient current going to the FET drain. This has that square/sawtooth shape as the FET switches on and begins to ramp up the inductor current. That's a pretty bit dI/dt jump that's dealt with by the 10uF cap that's closest to the FET. That cap would be far less effective if there were an inductor in its path.

You may be curious how to model a ferrite. The simple model uses 4 components, arranged as below:

From https://www.analog.com/en/resources/analog-dialogue/articles/ferrite-beads-demystified.html

In this article they analyze a selected bead and create a model for it, and show work to optimize its performance with damping.

For the input filter, it's important to have the capacitor close to the supply terminal, with a small loop area to GND. This cap supplies the high-side transient.

This would imply C-L-C-L-C input sequence as shown in the MPQ appnote to be preferred.

Layout matters too: minimize the loop areas for both the main input cap and especially the output cap. The fast currents in these paths have a profound influence on radiated emissions.

Here's a sim to play with (simulate it here):

You can see that the current ripple at the 5V input is pretty well knocked down by the double-pi filter.

But also take note of transient current going to the FET drain. This has that square/sawtooth shape as the FET switches on. At first it jumps up immediately, then ramps up with the inductor current build-up. That initial step is a pretty big dI/dt jump, that's handled by the 10uF cap that's closest to the FET. That cap's performance would be far less effective if it were placed with the inductor in its path.

You may be curious how to model a ferrite. The simple model uses 4 components, arranged as below:

From https://www.analog.com/en/resources/analog-dialogue/articles/ferrite-beads-demystified.html

In this article they analyze a selected bead and create a model for it, and show work to optimize its performance with damping.

For the input filter, it's important to have the capacitor close to the supply terminal, with a small loop area to GND. This cap supplies the high-side transient.

This would imply C-L-C-L-C input sequence as shown in the MPQ appnote to be preferred.

Layout matters too: minimize the loop areas for both the main input cap and especially the output cap. These have a profound influence on radiated emissions.

Here's a sim to play with (simulate it here):

You can see that the current ripple at the 5V input is pretty well knocked down by the double-pi filter.

But take note of transient current going to the FET drain. This has that square/sawtooth shape as the FET switches on and begins to ramp up the inductor current. That's a pretty bit dI/dt jump that's dealt with by the 10uF cap that's closest to the FET. That cap would be far less effective if there were an inductor in its path.

For the input filter, it's important to have the capacitor close to the supply terminal, with a small loop area to GND. This cap supplies the high-side transient.

This would imply C-L-C-L-C input sequence as shown in the MPQ appnote to be preferred.

Layout matters too: minimize the loop areas for both the main input cap and especially the output cap. These have a profound influence on radiated emissions.

Here's a sim to play with (simulate it here):

You can see that the current ripple at the 5V input is pretty well knocked down by the double-pi filter.

But take note of transient current going to the FET drain. This has that square/sawtooth shape as the FET switches on and begins to ramp up the inductor current. That's a pretty bit dI/dt jump that's dealt with by the 10uF cap that's closest to the FET. That cap would be far less effective if there were an inductor in its path.

You may be curious how to model a ferrite. The simple model uses 4 components, arranged as below:

From https://www.analog.com/en/resources/analog-dialogue/articles/ferrite-beads-demystified.html

In this article they analyze a selected bead and create a model for it, and show work to optimize its performance with damping.

For the input filter, it's important to have the capacitor close to the supply terminal, with a small loop area to GND. This cap supplies the high-side transient.

This would imply C-L-C-L-C input sequence as shown in the MPQ appnote to be preferred.

Layout matters too: minimize the loop areas for both the main input cap and especially the output cap. These have a profound influence on radiated emissions.

Here's a sim to play with (simulate it here):

You can see that the current ripple at the 5V input is pretty well knocked down by the double-pi filter. Also, look at the current going to the upper FET, which has that square/sawtooth shape as it switches on and begins to ramp up the inductor current. That's a pretty bit transient jump, that's dealt with by the cap that's closest to it.

For the input filter, it's important to have the capacitor close to the supply terminal, with a small loop area to GND. This cap supplies the high-side transient.

This would imply C-L-C-L-C input sequence as shown in the MPQ appnote to be preferred.

Layout matters too: minimize the loop areas for both the main input cap and especially the output cap. These have a profound influence on radiated emissions.

Here's a sim to play with (simulate it here):

You can see that the current ripple at the 5V input is pretty well knocked down by the double-pi filter.

But take note of transient current going to the FET drain. This has that square/sawtooth shape as the FET switches on and begins to ramp up the inductor current. That's a pretty bit dI/dt jump that's dealt with by the 10uF cap that's closest to the FET. That cap would be far less effective if there were an inductor in its path.