9 Nov
2011
9 Nov
'11
10:34 a.m.
On 11/9/2011 11:35 AM, David Riley wrote:
IIRC it uses an
open-collector arrangement of sorts, so it's not super-fast (though
that depends on what your metric for fast is), but it's great for I2C
level conversion. Not bad for other stuff, either.
Dave,
Once they are enabled (which can take max 7ns), the normal propogation
delay appears to be 250ps max. Doesn't sound too slow for most of my
applications.
The voltage drop is mosfet switch drop(5v-4v) + internal diode(4v to
3.3v) to do 5v to 3.3v. (I barely know what I'm talking about here)
@Scott: Right, the 3.3v passes through untranslated. Based on my limited
understanding, this should be ok. With Vih of 5v TTL being 2v, you're
good there. Over the Vt of 5v CMOS, but just under Vih.
This app note explains it well.
http://www.ti.com/lit/an/scda003b/scda003b.pdf
Thanks,
Keith