What to do with unused pins on a microcontroller?

What to do with unused pins on a microcontroller?

In a typical microcontroller design, it’s normal to end up with some unused pins. These may be general purpose inputs and outputs or pins that are merely labeled as “NC” in the datasheet. The quick and easy solution is to leave these pins unconnected as this means less routing for the hardware as well as less space occupied on the PCB.

What should I do with my unused MCU pins?

Leave the pin unconnected, set as an output, and driven high or low. This is nice because the pin is still available for future use, but accidental shorts could easily kill the thing. This is the worst case scenario for EMI, because each pin forms a tiny stub of an antenna. Set the pin as a input, connect the pin to GND or VCC.

What do NC pins mean on a microcontroller?

As for pins that are labeled ‘NC,’ the lack of standardization from the manufacturers means that you should always read the datasheet thoroughly before deciding if they are best left unconnected, or a resistor tied to ground or Vcc is required.

Is it safe to leave output pins unconnected?

Output pins are generally safe when unconnected, but it’s a good practice to connect them to pull-up instead of pull-down resistors to minimize idle currents. Having external resistors also means that heat dissipation is evenly distributed instead of concentrated on the microcontroller itself. Some pins are best left unconnected.

Which is the best software to terminate unused pins?

With comprehensive PCB design software like Altium Designer ®, terminating the unused pins with resistors is convenient. Altium’s offers all the necessary components and includes additional resources to help optimize your PCB design. If you have more concerns about unused pins, talk to an Altium expert for more tips.

What happens if you terminate an op amp?

Improperly terminating unused op amp pins has the potential to lead to degraded the op amp or system performance. Leaving either the input or output pins floating will create unexpected voltage shifts, which leads to unpredictable behavior.

When is a microcontroller pin configured as an output?

This section describes the basic characteristics of a microcontroller I/O pin when it is configured as a digital input. Most of a microcontroller’s I/O pins can be configured as an output or an input. Part 2 described the basics when a pin is configured as an output.

What happens when a microcontroller outputs a 0?

When the microcontroller (connected to “IN”), outputs a 1 then the transistor Q1 turns on. This turns on relay RL1 and the result is the lamp (R2), turning on. If the microcontroller outputs a 0 then the transistor Q1 turns off which disables the relay and therefore the lamp turns off.

How is a microcontroller connected to a transistor?

This simple circuit is handy for controlling high powered LEDs by microcontrollers where the microcontroller output is connected to “IN”. When the microcontroller outputs a 0 then the transistor Q1 turns off and so does the LED D1. When the microcontroller outputs a 1 then the transistor turns on and therefore D1 also turns on.