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alan smith wrote:
> The other week, the discussion under the topic of the iPod serial port, talked about the 5V to 3V interface, and of course the use of the voltage divider resistors, R1 in series, R2 to ground and where R1=2/3R2.
>
> However, just how robust is this?  I know, someplace I've seen and used dual voltage translators where you can have two independant Vcc and thus go
> from 5V to 3V (not 3.3) and feel pretty good that things are not going to go awry.  Not that I don't believe the resistor method works, it does but I have a sensitive circuit on the 3V side so I want to look at both options but...I can't find the chip(s) that do this.  There are several that do a 3.3V to lower voltages but I can't seem to lay my hands on the 5V to 3V devices.  Looked at Fairchild and NXP,..others?

Philips created a wonderfully useful level shifting circuit that's
cheaper than the ICs and nearly as simple as the resistor networks. It
takes a single N channel MOSFET and two resistors, performing both 3v ->
5v conversion and 5v -> 3v conversion. I've used it with many circuits
and have permanently modded my ICD2 to incorporate it.

To find the original app note, search for "AN97055".

(Sorry if this posts twice, I sent the message with the app note attached
the first time and I think it made it to /dev/null).

- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan {a} brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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