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If the frequency of the load exceeds the SMPS switching frequency, what are the results?

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    \$\begingroup\$ It won't be correctly regulated. But you should add some precisions for understanding your problem. I think that Buck converters in your PC/phone are probably working at 1 MHz. \$\endgroup\$ – Jess Mar 7 at 10:06
  • \$\begingroup\$ Your replies have convinced me of one thing: Using an SMPS for powering an RF circuit is definitely not advised. Thank all, you \$\endgroup\$ – Nexus Mar 11 at 3:55
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If the frequency of the load exceeds the SMPS switching frequency, what are the results?

If what you mean is the frequency of current drawn by the load...

Like any regulator, your SMPS controls its output impedance via feedback up to a certain frequency that is lower than the switching frequency. How much lower depends on the design. Above that, its output impedance is determined by the output capacitors.

So the regulator/SMPS handles the load current up to the frequency where output caps take over.

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For a HF load greater than HF SMPS source, the voltage regulator depends on the capacitance ratio of load to source. Otherwise a resistive load will draw all it's current from the low ESR output caps as the SMPS keeps charging it up. In some cases, you might use an RC filter to reduce load regulation ripple.

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  • \$\begingroup\$ All of this has convinced me of one thing: don't use SMPS for a system that operated up to 17 MHz! \$\endgroup\$ – Nexus Mar 11 at 3:58
  • \$\begingroup\$ It depends on rise time and voltage margin for ripple . If it switches faster than the slew rate of ripple, how bad is DC SNR? It’s a tradeoff that requires skill. \$\endgroup\$ – Tony Stewart EE75 Mar 11 at 11:00

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