Voltage Regulator Question

[brutus]

The March, 2005 datasheet of the LE00 low-dropout regulator is pretty new and says the ICs should have a bypass capacitor with an ESR from 0.1 to 10 ohms. Every schematic shown has a polarized output bypass capacitor.
Ceramic caps have an ESR much lower, and are not polarized.
Try a ceramic output bypass capacitor and tell us if the regulator oscillates.

Yes. You are right.

The guy from the chip company said:
"ceramic capacitors are needed for high frequency supression"
He said this regarding the chip I need to 'voltage regulate'

Will adding a 1 Ohm resistor in series to the ceramic cap solve this problem, and would it affect the ceramic caps' ability for  "high frequency supression"???

 

[audioguru2]

I think the "engineers" at the regulator manufacturer are thinking about ordinary regulators, not low-dropout ones. An ordinary regulator uses a ceramic cap for high frequency suppresion.

If you completely suppress high frequencies at the output of an older low dropout regulator then it will oscillate. Newer ones are supposed to have a resistor or something to stop oscillation when a ceramic output bypass cap is used.
The datasheet says the recommended range for the capacitor's ESR is from 0.1 ohm to 10 ohms and the ESR of ceramic cap is much too low. So sure, add a 1 ohm resistor in series to be safe.

 

[brutus]

Thanks!

I will do that.

I was a bit unclear... I meant the chip maker of the Qt301 that needs a ceramic cap for high frequency supression, not the regulator.

Anyways... this has been most educational.

I appreciate your help.

 

[audioguru2]

I was a bit unclear... I meant the chip maker of the Qt301 that needs a ceramic cap for high frequency supression, not the regulator.

Your choice of a low-dropout regulator that won't tolerate a ceramic output capacitor and your QT301 ICs that need a ceramic supply cap cause a conflict because they are not compatable.