Hi,

Some links.

Best regards,

Luciano

Interfacing 3V and 5V applications:
http://www.semiconductors.philips.co...otes/AN240.pdf

Voltage Level Conversion:
http://focus.ti.com/lit/an/swra071/swra071.pdf

* * *
5V to 3.3V and back from 3.3V to 5V
(Works down to 1.5V)

74LVC4245A Octal dual supply translating transceiver; 3-state
http://www.semiconductors.philips.co...LVC4245A_5.pdf

MAX3370/MAX3371 logic level translators
http://pdfserv.maxim-ic.com/en/ds/MAX3370-MAX3371.pdf

More level translators from Maxim:
http://para.maxim-ic.com/cache/en/results/5043.html

* * *

5V to 3.3V
Inputs can be driven from either 3.3 or 5 V devices.
(The 74LVC125A and 74LVC244A will not replace the 74LVC4245A or the MAX3370/MAX337).

74LVC125A:
http://www.semiconductors.philips.co...4LVC125A_4.pdf

74LVC244A:
http://www.semiconductors.philips.co...LVCH244A_4.pdf