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Unused Gates

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Wp100

Well-Known Member
Hi All,

I'm using an 8 bit bidirectional voltage translator chip, TX0108E, between a 5v Pic and a 3v3 device.

All is running well, but normally when you have unused gates on chips you tie them H or L - but wondered what is the best thing to do with the 2 pairs of unused gates I have on this chip ?

Nothing to give any suggestion in the datasheet, just wondered if leaving then open would cause any problems ?
 

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dknguyen

Well-Known Member
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THe datasheet says each I/O has a pull-up resistor inside the IC that are enabled whenever the IC is enabled so it seems you could just leave the pins disconnected. You can't just connect straight to +V or straight to ground since it would make a short-circuit whenever the pin was the opposite value. If you are not certain you could always just connect your own pull-up (or pull-down resistors) of a sufficiently high resistance to keep the pin from floating and dissipating too much energy. Or you could tie the inputs to a known value and leave the outputs unconnected- that should keep the I/O pins in a known state.

Personally, I'd be tempted to do the last thing if there were no internal pull-ups, since it takes no extra components.
 
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