Does anyone know what the effect is of a 3.3V input to inputs D, DE, RE^ if there is no power to Vcc1 of the chip? I want to power this chip from an external power supply and the signal from an internal one, and the external will sometimes be absent.
The data sheet recommended max input voltage is Vcc which implies - don't do it. However, the absolute max ratings are in terms of absolute voltage (+7V) not vcc so by this there should be a lot of headroom.
The equivalent circuit would imply a small leakage via a 1M resistor, but I have no idea if this circuit is valid for this analysis.
I am trying to avoid having a gating circuit for when the Vcc drops.
Any idea of whether its ok to allow an input when there is no Vcc?
Thanks
