How to source a circuit with 3,3v from USB?

[aldevan]

hi, I need to source a circuit with 3,3V x 120mA, I need to get the source from USB PC (5V) Does anyone can tell what LDO I can use?

regards

 

[pisoiu]

3,3v from USB

You can use LF33CDT from ST for example, but be carefull at those 5V from USB port. The voltage is not nice an clean...in many computers I found it very noisy, depending on the PC power supply, type and number of peripherals...etc. If you have bad luck, you may encounter cases when the voltage will drop below the minimum input voltage of a 3,3V LDO. Check the voltage with a scope.

/pisoiu

 

[alexz]

Re: 3,3v from USB

You might also need to indicate the self-powered type device in the one of the USB descriptors

 

[aNdreiBuuu]

Re: 3,3v from USB

the NCP3335 (with noise reduction) from onsemi (0.34USD @ 4K) it's a good choice:

https://www.onsemi.com/pub/Collateral/NCP3335 DATA SHEET.PDF
//a