Hi,
--> read the datasheet, it gives very detailed iformation about capacitor selection.
It begins with chapter 9.2.2.2
If you have additional capacitors, then you may seperate them by using a series R or series L.
Klaus
Thanks, in the datasheet it's written how to select true L and C for Buck converter but i didn't find a formula for the series R or L after the output. just saw
"Super-capacitors can be used in parallel to the ceramic capacitors when it is made sure that the super-capacitors series resistance is large enough to
provide a valid feedback signal to the error amplifier which is in phase with the inductor current."
How much is high enough ?!
I have 2 buck converters and one booster in my whole circuit, one buck is for MCU which is always on, another buck for GSM module which is Enabled/Disabled by MCU, and one booster to provide higher voltage for an output device which it's input is connected to output of GSM buck.
As datasheet says, input capacitors can be higher.
For MCU buck, i can use R series after the TPS output because the whole current consumption is low, maximum around 1-2mA in working mode and small uA in sleep times. (i don't know how much R is enough Exactly ?!)
But for GSM module which has up to 1.8A surge current consumption, i can't use resistor (because of high drop voltage), as you said, i can use series L too, i need to use some high value capacitors near GSM module to provide the source for surge currents.
Now how should i calculate that series L value ?! (in datasheet only L value formula for Buck or Boost converter circuit is written).
Won't that series L in output make instability like more C ? (in datasheet just said about more R for output C)
Thanks again