5V to 3.3V micropower voltage regulator

[amitkoolkarni1]

hello,
For a microcontroller programmer using USB port ineeded to convert 5v to 3.3V,initially one of the micropower voltage regulator,LP2950CZ-3.3,wasn't available which was the supposed regulator,so i used LM1086 CT 3.3V,its o/p current is 1.5A as compared to LP2950 which had 100mA.Initially it gave me an output of 3.3V,but later it started giving me 4.0V which was undesirable for the USB controller IC whose max limit is 3.6V.A 100nF capacitor is connected at the input side,and 10microfard at the output.Another IC which i have used is MAX734,which also taakes its input of 5.0V from USB,has a capacitor at i/p side which is of 47microF,its o/p was expected to be 13V but it is decreased to 12.12V.
Please solve my problem.

[Al_Dodge_Bundy]

Here's some example how to use the LM1086 with a regulated (in your case 3.3 V) output voltage:

http://www.jlink.com.tw/Datasheet/HTC/LM1086T,R-X.X.pdf

The example on page 1 has an output voltage of 3.3 volt, so you can use the resistors as noted in the document.

Good luck,

Mark

[Guest]

DEAR ALL,
THE POWER ON THE USB PORT IS LIMETED (500MA AT 5V) OS ONE NEEDS TO USE A HIGH EFFICIENCY CONVERTER !!! I.E SYNCHRONOUS BACK TOPPOLOGY . I USED lINEAR TECHNOLOGY PART :
LTC3411EFE THIS GAVE ME 95% EFFICIENCY AND I WAS ABLE TO WPRK EASILY . THIS GUYS ALSO HAVE SPECIAL CHARGERS THAT WORKS OFF THE USB PORT. (THE CURRENT IS LIMITED AND ONE CANNOT LOAD THE PORT !! SEE ALSO lLT1618
br
kg

[Marcin Bobowicz]

this is one of the most popular voltage regulators. I don't know why you didn't try this. 7803 is for 3V and 7805 is for 5V. There is more of them-ask a dealer for the most suitable for you or just check description (google helps a lot )