I'm supplying 12 V to my 9476 (and have verified this by measuring at the pins). When I toggle any one of my DO channels I see the 12 V when I'm at logic high, but when I set it to low I'm seeing about 7.75 V. I wouldn't be surprised, I suppose, to see some amount of voltage when low, but that's nearly 2/3 or the supplied voltage. I have some level shifters that some of these channels are connected to and that 8V is preventing the shifted voltage from being anything but logic high.
So my questions:
- When I output a zero on one of my 9476's lines is it actually supposed to output a low level or is it instead floating the line (and therefore requires a pulldown resistor at the output)?
- If it is supposed to output an actual voltage, why on earth is it so high relative to the Vsup?
Thanks!