What is the benefit and role of pull up and pull-down resistors in CMOS andin the input and output pins?

What is the benefit and role of pull up and pull-down resistors in CMOS andin the input and output pins?

A pull-up resistor allow controlled current flow from supply voltage source to the digital input pins, where the pull-down resistors could effectively control current flow from digital pins to the ground. At the same time both resistors, pull-down and pull-up resistors hold the digital state either Low or High.

What is the problem with using a pulldown resistor with a very low resistance?

Pull-up resistor value If the resistance value is too low, a high current will flow through the pull-up resistor, heating the device and using up an unnecessary amount of power when the switch is closed. This condition is called a strong pull-up and is avoided when low power consumption is a requirement.

Why use pull-up resistor instead of pull-down?

A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH. Pull-down resistors are a little more critical because of the low input voltage level, VIL(max) and the higher IIL current.

Why do we need pull-down resistors?

The pull-down resistor holds the logic signal near to zero volts (0V) when no other active device is connected. It pulls the input voltage down to the ground to prevent an undefined state at the input. Unlike the pull-up resistor, the pull-down resistor pulls the pin to a low value instead of high value.

Which port has no built in pull-up resistor?

P0 port
Input/Output (I/O) pin − All the circuits within the microcontroller must be connected to one of its pins except P0 port because it does not have pull-up resistors built-in.

What happens if the pull-up resistor for an I2C signal is too large?

If your pull-up resistor is too large, then it won’t be able to overcome the leakage current. If it just barely overcomes the leakage current, then any noise in the circuit could be enough to change the input.

What does VCC stand for?

Voltage Common Collector
VCC (Voltage Common Collector) is the power supply of a device .

How many pull-up resistor are used in port 0?

Full Member level 5. Pull-ups are used so that components with a different driving voltage can be connected to the microcontroller.

Which port is required to be connected to 10k ohm pull up resistors?

[SOLVED] Why in port 0 each pin must be connected to 10k ohm pull-up resistors in 8051?

Does SPI need pullup resistors?

For the SPI operation no pull-ups are needed. Unlike the I2C where pull-ups are needed because the drivers have open collector outputs, no pullups are needed on the SPI signal lines since the drivers have push-pull outputs.

Why do you need pull up resistor?

In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal. It is typically used in combination with components such as switches and transistors , which physically interrupt the connection of subsequent components to ground or to VCC.

What is a weak pull up resistor?

A low resistor value is called a strong pull-up (more current flows), a high resistor value is called a weak pull-up (less current flows). The value of the pull-up resistor needs to be chosen to satisfy two conditions: When the button is pressed, the input pin is pulled low.

Does an output require a pull down resistor?

Another application is the I2C protocol bus, where pull-up resistors are used to enable a single pin to act as an input or an output. When not connected to a bus, the pin floats in a high-impedance state. Pull-down resistors are also used on outputs to provide a known output impedance. Power resistor.