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How do you calculate bus capacitance?
The bus capacitance is determined by many factors, mainly the bus layout and the slaves. The general rule is that each slave on the bus will contribute about 15 pF of capacitance. Another general rule (albeit, very rough), is that 3 pF/cm of PCB trace.
What is the maximum bus length of I2C?
So the maximum bus length of an I2C link is about 1 meter at 100 Kbaud, or 10 meters at 10 Kbaud. Unshielded cable typically has much less capacitance, but should only be used within an otherwise shielded enclosure.
Is I2C a bus?
I2C stands for Inter-Integrated Circuit. It is a bus interface connection protocol incorporated into devices for serial communication. Recently, it is a widely used protocol for short-distance communication. …
What is meant by I2C bus?
I2C (Inter-Integrated Circuit, eye-squared-C), alternatively known as I2C or IIC, is a synchronous, multi-master, multi-slave, packet switched, single-ended, serial communication bus invented in 1982 by Philips Semiconductors.
How far can I run I2C?
What is the maximum distance of the I2C bus? This depends on the load of the bus and the speed you run at. In typical applications, the length is a few meters (9-12ft). The maximum capacitive load has been specified (see also the electrical Spec’s in the I2C FAQ).
Where is I2C bus used?
The I2C bus protocol is most commonly used in master and slave communication wherein the master is called “microcontroller”, and the slave is called other devices such as ADC, EEPROM, DAC and similar devices in the embedded system.
What’s the maximum capacitance of an I2C bus?
Then the maximum bus capacitance is: For Trise_max = 1000 ns = 1 µs and Rpullup_min = 1.1 kohm, Cbus_max is on the order of 750 pF so you have to fall back on the specification maximum of 400 pF. As a practical matter, one can put up to about 10 devices on an I2C bus without too much problem.
How is the pull up resistor of an I2C bus limited?
The maximum pullup resistance is limited by the bus capacitance (Cb) due to I2C standard rise time specifications. If the pullup resistor value is too high, the I2C line may not rise to a logical high before it is pulled low.
What is the maximum capacitance of a bus?
As the number of devices connected to the bus increases, the bus capacitance also increases (I think the maximum allowable capacitance is 400pf). To bring the bus to a logic 1, a pull up resistor is connected on SDA and SCL lines.
Why is copper trace capacitance important in I2C?
Copper Trace Capacitance When we say “copper trace capacitance” here, we’re referring to single trace over dielectric over ground. The capacitive coupling between the I 2 C signal lines and the ground plane can be significant if the ICs are far from each other, or multiple ICs are on the I 2 C bus.