Logic family compatibility



I spent a few days doing homework on what logic family and voltage was compatible with what. This was a lot of work because each vendor has their own spin on the specifications (which makes me wonder why standards even exist, but that is another story).

Below is my take on things, and I would appreciate your comments if I have it wrong, or something is incomplete.

I refer to CMOS, NMOS, etc. as xMOS.

From         To
----         -----------------------------------------------
TTL:         TTL; LVTTL*; 3.3V xMOS*, LCX*, LVC*; LVT*, LVX*

LVTTL:       TTL**; LVTTL; 3.3V xMOS, LCX, LVC; LVT, LVX

xMOS, 5V:    xMOS 5V; 3.3V xMOS*, LCX*, LVC*; LVT*, LVX*

xMOS, 3.3V:  TTL; LVTTL; 3.3V xMOS, LCX, LVC; LVT, LVX

'L's, 3.3V:  TTL**; LVTTL**; 3.3V xMOS, LCX, LVC; LVT, LVX

*5 volt tolerance required, which they all seem to have today.

**Make sure that the Ioh is high enough to drive the loads.

Driving 5 volt xMOS is difficult because the Vih is .7Vcc, or about 3.5 volts. Thus, a 3.3 volt part can't do this without a device like a 74LVC4245 or 74LVX4245.

.



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