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While choosing some buck regulators I came upon some models that have a pin which selects the switching frequency between 2 values; take TPS629210 or TPS62913 for example. I'm just a hobbyist and not a pro on analogs but generally I thought higher switching frequency is always better (correct me) and low-frequency regulators are just old models:

  • Tiny inductors
  • Better regulation/current limit (cycle-by-cycle operation means quicker response to changes)
  • Easier to filter; many components don't even need filtering high frequency noises if they appear. For example, MCP1501 buffered voltage reference: MCP1501 datasheet about noise

So basically when I was going to choose a model, I would go with a hobbyist-friendly* regulator with the highest frequency available. What is the benefit of a low-frequency regulator when high-frequency models exist?

Hobbyist-friendly: a regulator which doesn't need much calculation to work properly.

High-frequency: anything over 0.8 MHz

Low-frequency: well anything under that

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  • \$\begingroup\$ What is the unit of measurement that you are using to determine that higher frequency is, "better"? \$\endgroup\$ Commented Jul 11 at 18:04
  • \$\begingroup\$ @StephanSamuel The 3 dotted sentences in the post. of course that's my basic understanding from it. \$\endgroup\$ Commented Jul 11 at 18:20

2 Answers 2

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These chips hard switch. This means that switching losses increase in proportion to frequency. The switching losses can be more than the conduction losses. There is a clear trade off between efficiency and frequency, high frequency will not give you the lowest chip losses. Low frequency keeps the chip cool but needs larger filter components. If the chip is running well below its rating then high frequency could give small filter parts and reasonable chip junction temps for good reliability. So the optimum frequency all things considered is application dependent which the chip makers know so they provide some select options whilst keeping pin count down.

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It depends on what property is important.

The data sheets for those regulators give an example to minimize switching losses they drop frequency to be more efficient at low output voltages.

If you value high frequency for making the inductor as small as possible or best filtering the ripple, it may apply only when you consume a lot of current and the chip works in CCM mode or forced PWM mode.

With light loads it only pulses when needed by skipping pulses and you get larger ripple.

These regulators will drop their switching frequency if needed based on the source and load anyway.

Larger uH inductor has less ripple, but you are right in that it will also react slower to load steps.

So higher frequency does come with a cost, and the chips have to be more complex and switch between different modes of operation for whatever property you might value over other property (size, ripple, emitted spectrum, efficiency, load step response etc).

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