Contents
What does it mean to leave a pin floating?
Leaving a pin configured as an input floating is dangerous simply because you cannot be sure of the state of the pin. Like you mentioned, because of your circuit, your pin was sometimes LOW or sometimes in no-man’s land or could sometimes go to HIGH.
Can the design have floating output pins?
Yes. You should always connect un-connected input pins. Un-connected output pins are not a problem and can be left as such.
What do I do with unused IC pins?
General “rule of thumb” for unused IC pins
- Provide a solder pad/hole so the chip is secured but leave pin floating.
- Connect the pin to ground (possible through a resistor/capacitor/etc.)
- Connect the pin to a supply source.
- Something I can’t possibly think of.
What are floating inputs?
If an input is floating, it will be “high impedance”. Therefore it will be flipping up and down at random, perhaps picking up stray RF etc. So tie the pin to ground or rail and it can’t do that. Leaving an input floating is a recipe for much unhappiness. 9/19/2009.
What does a pull-up resistor do?
In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal. A pull-up resistor effectively establishes an additional loop over the critical components, ensuring that the voltage is well-defined even when the switch is open.
What does it mean when an input floats high?
What does it mean when an input floats high? It means that you can not come to a conclusion on the input.
How does a floating pin affect a circuit?
One of the most basic of the faults is the infamous “floating pin” or “floating input” that can affect the I/O pins of digital integrated circuits. To best explain a floating input and how it can negatively affect your project consider the circuit in Figure 1:
Do you think floating pins are a good thing?
Now, usually you might think, hey, if something’s floating, that’s like a good thing. Your ship crashes, you’re floating in the ocean and hey, you’re floating that’s better than sinking, right? Well, with electronics that’s not the case. Think about hairdryer in the tub, that doesn’t necessarily mix. So, the bottom line is floating pins are bad.
Is it bad to leave unused pins in a circuit?
In general, unused inputs should not be left open circuit: Digital circuitry often has inputs that are used to configure its operation and are permanently connected to Logic 0 or Logic 1.
When to connect unused pins to logic input?
If an unused logic input has internal pull-up or pull-down resistors/currents, it is not necessary to connect to the pin, but if the pin is likely to be exposed to electrostatic or RF fields, it may be sensible to do so by making an external connection to V DD or V SS, respectively 7.