5V supply LC Filter question and help

Thread Starter

QMESAR

Joined Dec 9, 2017
15
Hi All
I am using a TLE4284D Linear Regulator in an automotive supply for the mcu and other components on the pcb,
from the Infineon Datasheet and / LDO application Note it is essential to have a reverse polarity protection diode at the VIN and a 100nF Ceramic capacitor with a 40V TVS diode,At the VOUT it is essential to have at a minimum a X5R or X7R dielectric ceramic capacitor of 10uF (min)
with this said would you recommend using the LC fitter after the minimum requirements of the LDO or should I place C1 after the LC filter as shown in my preliminary schematic

Any help or suggestion is highly appreciated


1.JPG

Regards
QMESAR
 
Last edited:

Thread Starter

QMESAR

Joined Dec 9, 2017
15
Hi,
Thank you for your reply ,
I am only designing on paper at the moment however I would like to make sure if and when the first HW is available that if we have surge and
load dump conditions ( its an automotive application and Automotive can have large inductive kick back signals on the supply line ,so not sure I need it but I would like to have it as a backup in case .
so let say I am looking into the possibilities to make sure I can provide the on board components with a stable 5V supply in most or all cases .
What I would also like to ask is what is a sensible cuttof frequency for a Power Supply LC Filter 2Khz or 20Khz for example

Again thank you for your interest appreciated
QMESAR
 
Last edited:

crutschow

Joined Mar 14, 2008
34,285
For load dump voltages you need protection on the regulator input.
The output is not significantly affected by this dump.
 

Thread Starter

QMESAR

Joined Dec 9, 2017
15
Thank you for your answer.

Well that is what I am trying to do with the 40V TVS at the input ,not sure if there are other more sufficient ways to do load dump ?
Well yes I have read in the Infineon Application note for the LDO that they are quite stable as long as the Input voltage is higher than the output voltage up to the max input voltage of the LDO, .which is 40V in this case,maybe the LC is not needed however that is what I am looking for is to get some direct answers from experience people like yourself,
 
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