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TPS53319 ripple injection circuit with electrolytic and ceramic output capacitor

K. Sasaki14
Guru 10200 points

Is ripple injection circuit needed if we use both electrolytic and ceramic capacitor for output capacitor?
I think total ESR of output capacitor becomes very low when several ceramic capacitor are used.
In this case, how can we judge that ripple injection circuit is needed or not?

Best Regards,
Kohei Sasaki

  • 0
    TI__Guru**** 191445 points
    For mixes output capacitors, the transfer function no longer contains a simple ESR zero. Now there is a zero / pole / zero combination. The resulting output ripple voltage will likely be too small and not the characteristic triangle wave shape obtained when the inductor ripple current flows the through the relatively high ESR of an electrolytic capacitor. You will almost certainly need to use external ripple injection.