Filtering for USB5V

[Rajinder]

Dear all,
I am doing a project that powers off a USB port I.e. 5V. This will be used to get a clean 5V line, generate a 3.3V from LDO and also a -5V supply using a charge pump IC. I know that USB5V is noisy.
Could someone give me ideas on filtering this. I have seen pi filter arrangements but do not understand them fully.
Best regards,
Rajinder

 

[dorke]

What is "clean"?
First thing is defining the noise level you need to achieve.

 

[Rajinder]

What is "clean"?
First thing is defining the noise level you need to achieve.

Hi thanks for your message. I am using the USB5V to obtain a 3V3 supply, 5V and -5V supply. Also to supply voltage to power up a external reference for a DAC. The 3V3 will power the DAC and microcontroller. I have not yet monitored the USB5V supply line for noise but will do. But I have some sensitive circuitry which I can't have affected by noise etc.
My question was if anyone could tell me or show me how to filter out noise using a pi filter eg a tutorial or similar. Then I could use this to help me with my project.
Best regards,
Rajinder

 

[davenn]

I have not yet monitored the USB5V supply line for noise but will do.

well, as dorke said you need to know 1) what the noise level is and 2) what is the equip ratings

without info on those 2 things, any further discussion is pointless

the numbers are needed


Dave