Why should unused gate inputs be properly terminated?
Necessity for terminating gates There are a number of reasons for this: Gates may switch randomly: The voltage on an input that is not connected, i.e. floating is indeterminate. Open inputs to used chips and gates may cause random states: Even though many logic inputs tend to float high, this should not be assumed.
What should be done to unused inputs in TTL gates?
What should be done to unused inputs on TTL gates? They should be left disconnected so as not to produce a load on any of the other circuits and to minimize power loading on the voltage source. All unused gates should be connected together and tied to V through a 1 k resistor.
What is unused input?
Real unused logic inputs are ones whose logic state does not affect the particular application required—these should be connected to fixed Logic 0 or Logic 1 potentials and not left floating6.
How will you handle unused inputs in a logic gate logic Ic?
74HC/HCT: What to do with unused inputs and why?
- connect them directly to Vcc.
- connect them directly to GND.
- connect them to Vcc through a pull-up resistor.
- connect them to GND through a pull-down resistor.
Is it safe to leave unused inputs 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.
What to do with unused pins on a microcontroller?
Connect unused input pins to pull-up or pull-down resistors. Some would claim that connecting the unused pins to ground or Vcc would be the best way to eliminate the risk of EMI interference.
What should be done with an unused TTL input that is required to be at logical 1?
What should be done with an unused TTL input that is required to be at logical 1? It should be left disconnected. It should be tied to the positive supply rail through an appropriate resistor.
Why is it not recommended to leave unused logic inputs floating what should we do to such inputs in the case of TTL and CMOS logic gates?
Do not leave them floating as then they will be in an undefined state and susceptible to external influences and can cause high current consumption or oscillation. It shouldn’t make any appreciable difference whether you tie them high or low for a standard logic gate, so long as they are tied somewhere.
What should be done with the unused input of a CMOS integrated circuit when it is connected to a circuit?
Generally, all unused inputs should be tied to either VCC or GND. However, any pins of bidirectional bus buffers (e.g., Function 245) that can be configured as an output (e.g., bus pins) should be tied to VCC via a pull-up resistor or to GND via a pull-down resistor.
Why is it bad to practice leaving logic gate inputs?
Why should we avoid floating inputs?
The short circuit could generate enough heat to damage your circuit. Or at the very least cause power supply voltage to drop to ground potential resulting in a non-functioning device. In short, bad things will happen.
Which of the following logic families has the shortest propagation delay?
5. Which of the following logic families has the shortest propagation delay? Explanation: AS-TTL (Advanced Schottky) has a maximum clock frequency that is 105 MHz. So, the propagation delay will be given by 1/105 sec which is the lowest one.
