??? 04/22/10 17:35 Read: times Msg Score: +1 +1 Informative |
#175282 - is a Zener that costly? Responding to: ???'s previous message |
in the Datasheet it mentions that maximum Vhigh on any I/O pin is Vcc+0.5V and Vlow is -0.5V)this 0.5V i assume is the forward Voltage drop of internal clamp diodes.
ABSOLUTELY NOT!!! Maximum ratings specify is that the chip will not burn if these vaules are not exceeded. Parasitic diodes MAY be present in some chips, but when not specified, there is no guarantee. Anyhow if you use my suggestion of an XOR, the 74H chips are specified to withstand some current (20mA?) when driven outside the limits. Erik |