Designing a buck converter

[RenoX]

I’m working on a project where I need to step down 24V to a stable 5V with a load current of up to 1A. I’ve decided to use a buck converter based on the LM2675 IC. Here is my schematic made in DipTrace:


Input: 24V (DC)
Output: 5V / 1A
Controller: LM2675
Switching Frequency: 260 kHz
I’m planning to use two capacitors:
Input Capacitor (C1): To smooth the input voltage and suppress noise.
Output Capacitor (C2): To smooth the output voltage and minimize ripple.
I have the following questions and concerns:
Type and value of the input capacitor: I’m considering using a 100 µF electrolytic capacitor with low ESR, but I’ve heard that ceramic or polymer capacitors might be better for high-frequency applications. Which type would be optimal for input noise suppression?
Type and value of the output capacitor: Given the need to minimize output ripple, should I use multiple low ESR ceramic capacitors or a single large electrolytic capacitor? Or perhaps a combination of both?
Impact of switching frequency on capacitor selection: How does the 260 kHz switching frequency affect capacitor choice? Should this be a factor when determining capacitance?
Temperature stability: The system will operate at elevated temperatures (up to 70°C). Which type of capacitor is best suited for these conditions?
I’d appreciate any advice or suggestions! I’m especially interested in hearing from anyone who has experience with similar circuits.
By the way, how do you like DipTrace 5? Has anyone tried working on it yet?

 

[Delta Prime]

Very good for makers and hobbyists.  Inexpensive,negligible learning curve.
With that said,DipTrace 5.0 (Beta) people start learning from the top down, which leads to frustration; they get lost in spice simulation circuit analysis because they are missing a prerequisite.
Basic electronic component theory:
resistors, capacitors, and inductors.
They don't bother to look up DC/DC
Step down converters power supply filters.

 

[Delta Prime]

LM2675 input capacitance - Power management forum - Power management - TI E2E support forums

Other Parts Discussed in Thread: LM2675 I'm designing a simple switcher circuit using a LM2675 to generate 3.3V at 1.0A from 24V. The LM2675 datasheet shows a graph

e2e.ti.com

 

[Harald Kapp]

RTFM.
The datasheet has a section (9.2.1.2.2) on output capacitor selection.
There is more information on all the other external components in chapter 9, too.

up to 70°C

Is that the ambient temperature of the capacitor? Or is it the ambient temperature of your device? If the latter, you need to account for an increased temperature within the housing. How much depends in your design, power dissipation, method of cooling etc. You may need to measure this. If you can't measure, make an educated guess, e.g. 20 K above the device's ambient temperature. That would put the components within the device at 90 °C. ALL components need to be specified for operation at this temperature (or higher).
For the electrolytic capacitor this results in a 105 °C type at the minimum.

 

[Andrewerry]

You should read the LM2675 datasheet carefully about choice of inductor, capacitors and layout - because such things are picky.