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TIDM-1001: (Reference design) Input and output filter capacitor design and selection

Part Number: TIDM-1001

Hi, engineers,

Do you mind sharing the method or experience of selecting input capacitance and output capacitance in the reference design, or can you explain the reasons for your selection of input and output capacitance values and their capacitance combinations?

Or can you point out the problems I have in selecting input and output capacitors?

When I select the input capacitor, according to the input voltage ripple requirements, through the simulation design of a set of capacitance value and ESR combination, through the simulation will also get the effective value of the input capacitor current; then, the required capacitance is selected from the capacitance that meets the voltage index. At this time, the effective current value of the capacitance can be considered at the same time. If a single capacitance is difficult to deal with the effective current value of the capacitance current obtained by simulation, I will select several capacitors in parallel to obtain the input capacitance (of course, the volume of the input capacitance is also taken into account); in addition, the parallel connection of capacitors will reduce the parasitic resistance and parasitic inductance, which is part of the reason for the parallel combination of capacitors.

The problem in my method of selecting input capacitance is according to me, the input capacitance will be several same capacitors in parallel, but the input capacitance combination in TIDM-1001 is the capacitance combination with large difference in capacitance. Can you explain the reason?

When I select the output capacitance, the selection method is the same as the method of selecting the input capacitance. Is there anything that needs further consideration? I probably understand that the output filter capacitor and its parasitic parameters also affect the load transient performance.

Look forward to your time to reply, thank you!

Mr. Luo