# How do you select a pull-up resistor for I2C?

## How do you select a pull-up resistor for I2C?

The I2C bus must have pull-up resistors, one on the SDA line and one on the SCL line. They’re typically 4.7K or 10K ohm, but should be in the range of 2K to 10K. Many of the breakout boards you can buy at Adafruit or SparkFun already have the pull-up resistors on them, typically 10K but sometimes 4.7K.

## How many pull-up resistors for I2C?

two
The I2C specification allows a maximum of 3 mA pull-up current on each I2C line. The Aardvark adapter has two internal pull-up resistors on each line: 2.2k ohm and 100k ohm resistors in parallel. The 2.2k ohm resistor can be turned on and off.

What is pull-up resistor in I2C?

A pull up resistor is used to provide a default state for a signal line or general purpose input/ouput (GPIO) pin. Typically they are of high resistance thousands or tens of thousands of ohms of resistance.

How would you go about picking pullup resistors for an I2C bus?

Notice the two pull-up resistors on the two communication lines. Resistor selection varies with devices on the bus, but a good rule of thumb is to start with 4.7kΩ resistor and adjust down if necessary. I2C is a fairly robust protocol, and can be used with short runs of wire (2-3m).

### How do you find the pull-up resistor value?

Calculate actual values of pull up and pull-down resistor In order to calculate pull-up and pull-down resistance, we need to first apply the formula in Ohm’s Law: Resistance = Voltage/Current, or R= V/I.

### How do you determine the value of a pull-up resistor?

A rule of thumb is to use a resistor that is at least 10 times smaller than the value of the input pin impedance. In bipolar logic families which operate at operating at 5 V, the typical pull-up resistor value is 1-5 kΩ. For switch and resistive sensor applications, the typical pull-up resistor value is 1-10 kΩ.

How do you calculate pull-up resistors?

In order to calculate pull-up and pull-down resistance, we need to first apply the formula in Ohm’s Law: Resistance = Voltage/Current, or R= V/I.

What pull-up resistor do I need?

Pull-up resistors are resistors used in logic circuits to ensure a well-defined logical level at a pin under all conditions. Without the pull-up resistor, the MCU’s input would be floating when the switch is open and pulled down to a logical low only when the switch is closed.

#### What is a pull-up pull-down resistor?

Pull-up Resistor Summary A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH. A pull-down resistor connects unused input pins (OR and NOR gates) to ground, (0V) to keep the given input LOW.

#### What is pull-up resistor?

Pull-up resistors are fixed value resistors used between the connection of a voltage supply and a particular pin in a digital logic circuit. More commonly paired with switches, its purpose is to ensure the voltage between Ground and Vcc is actively controlled when the switch is open.

What is pull-up and pull-down device?

Answer: Pull-up and pull-down are methods of processing digital signal lines by connecting them to the power supply side and ground side, respectively. Signals may be connected directly or via a resistor.

Why use 10k pull-up resistor?

Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels, if external devices are disconnected or high-impedance is introduced.

## What is the I2C pull up resistor value?

According to the I2C bus specification The I2C pull up resistor value mainly depends on the I2C mode (Standard / Fast / Fast Plus / HS), VDD and the bus capacitive load. I have built an online tool for sizing the pull up resistor at different bus modes.

## Why do I need an external pull-up resistor?

Instead of having outputs that can pull up and down, and open drain outputs can only pull down. That is why the external pull-up resistor is required. There are now additional restrictions on the range of pull-up resistors; the pull-up value will form an RC circuit with the bus capacitance.

Does the I2C bus consume a lot of power?

If there will be a lot of communication on the I2C bus, that power consumption may end up being a significant portion of overall power drain especially if the bus may sit low for extended periods of time.

Which pull-up resistor for SDA bus?

The SDA bus requires a pull-up resistor to VCC (typical 10 kΩ for 100 kHz, 2 kΩ for 400 kHz and 1 MHz). I thought that any resistor with a kΩ value would do the job (and it seems that my EEPROM works fine at different frequencies with a 10 kΩ resistor).

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