In the pulled-down configuration, the inputs are triggered by a high voltage level (Active High).
Pull-up resistors:
- Function: A pull-up resistor connects a signal line to a positive voltage source (such as Vcc). When a switch or input device is open or not connected, the pull-up resistor ensures that the signal line is at a known high logic level.
- Example: In a microcontroller input pin, a pull-up resistor can be used to ensure that the input is at a defined logic level when no external device is connected. For instance, if a button is connected to a microcontroller input pin, when the button is not pressed, the pull-up resistor keeps the input pin at a high logic level.
Pull-down resistors:
- Function: A pull-down resistor connects a signal line to ground. When a switch or input device is open or not connected, the pull-down resistor ensures that the signal line is at a known low logic level.
- Example: In a digital circuit, a pull-down resistor can be used to ensure that an input signal is at a low logic level by default. If an input signal is left floating without a pull-down resistor, it can pick up random electrical noise and cause unpredictable behavior in the circuit.
Pull-up and pull-down resistors help to stabilize signals, prevent floating inputs, and ensure that circuits operate correctly and predictably. The value of the resistor is chosen based on factors such as the required current, voltage levels, and the characteristics of the connected devices.
