Why pull-up resistor is used in I2C?
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Why pull-up resistor is used in I2C?
Why is a pull-up resistor used in I2C? Because there are only 2 logic level outputs from I2C, Low and open circuit. The default condition is all chips on the line are in open circuit mode, and the pull-up resistor makes the line high. The master chip can send an address signal to one of the chips on the line.
Are pull up registers required in I2C?
SDA and SCL lines of I2C pins needs pull up resistors for sure. Open drain and Open collector terminals needs pull up resistors to maintain the logic levels stable.
Why pull-up resistor is used in 8051?
To ensure the values of an I/P is always in a known state, pull up and pull-down resistors are used. The main function of pull-up and pull-down resistors is that the pull up resistor pulls the signal to high state unless it is driven low; and, a pull-down resistor pulls the signal to low state unless it is driven high.
How do you determine the pull-up resistor for I2C?
These pull-ups would draw 3.3V / 1.77 k = 1.86 mA each when SCL / SDA is low. So, theoretically, if this bus has the absolute maximum amount of capacitance on it, this bus should use at least 1.77 k Ohm pull-up resistors, down to 171 Ohm resistors if their maximum low drive strength is 13.5 mA each during SCL/SDA low.
How does a pull-up and pull-down resistor work?
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 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 is pull-up and pull down transistor?
Pull-up and pull-down transistors are at the output of CMOS logic gates. Pull-up transistor will act as a source when the output is logical high. The pull down transistor will act as a sink when the output is logical low.
What happens if a pull-up resistor is too large?
If the pull-up resistance value is too high, combined with a large leakage current of the input pin, the input voltage can become insufficient when the switch is open. This condition is called having a weak pull-up.
What is pull up and pull down network?
PullUp and PullDown. Pullup – a network that provides a low resistance path to Vdd when output is logic ‘1’ and provides a high resistance to Vdd otherwise. Pulldown – a network that provides a low resistance path to Gnd when output is logic ‘0’ and provides a high resistance to Gnd otherwise.