9 Nov
2011
9 Nov
'11
11:03 a.m.
On 11/09/2011 07:25 AM, Keith Monahan wrote:
I'm anxious to build a PCB that is based around a
pair of these
http://www.ti.com/product/sn74cbtd3384
10-Bit FET Bus Switches With Level Shifting
for a level conversion app.
I sampled some, although there was only the .635 pitch 24 SSOP/QSOP
version
available.
Note that these aren't active translators. The "level shifting" in the
5V to 3.3V direction is just the pass FET being turned off, which means
that the 3.3V you get out can be slightly squirrelly. It's generally
fine for CMOS digital inputs, There is no level shifting at all in the
3.3V to 5V direction, they just pass the 3.3V signal through. There's
nothing wrong with that as long as you're aware of it.
What these parts do is not any different than other commonly available
"QuickSwitch" parts, such as those from IDT and Pericom, and you can get
those in many packages, including SO. Most of those do not have the
diode internally, so this TI part does save one component, but that
wouldn't excite me enough to switch from SO to SSOP if I didn't already
want SSOP for some other reason.
Eric