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What pull-up resistor do I need?
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.
How many pull up resistors for I2C?
I2C Current Specifications and Bitrates 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 the difference between pull-up and pull-down resistor?
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.
Why external pull up resistance is used in l2c?
I2C and other protocols like it use “open drain” (or “open collector”) outputs. 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.
Is there a correct resistance value for I2C pull-up?
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).
What’s the smallest resistor for an I2C bus?
An 18K resistor represents the largest resistor we could use for pullup resistors on the I2C and SPI Education Shield (because 18K would work for both buses, no need to use two different values). Conversely, a 1K5 resistor is the smallest value we could use without burning up the I2C pins of our devices.
When do pull up resistors pull the line high?
The pullup resistors pull the line high when it is not driven low by the open-drain interface. The value of the pullup resistor is an important design consideration for I2C systems as an incorrect value can lead to signal loss.
How are pull up resistors used in VCC?
From Vcc through your pull up resistors! Your circuit and your pull up resistor form a big RC network (resistor / capacitor not remote control) that governs the charge and discharge rate of your capacitor. Now, mind you, this is a teeny, teeny capacitor.