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What is the pull-up resistor value for I2C bus? Issue Date：2015-04-23
For the standard-mode I2C-bus system, the resistor value Rp in the figure above is determined by the following parameters:
- I2C speed;
- Supply voltage;
- Bus capacitance;
- The number of connected devices (input current + leakage current).
The supply voltage (VDD) and the maximum output LOW level determine the minimum value of pull-up resistor Rp.
For example, a supply voltage of 4.5V, VOL= 0.4 V and Rp is 4.7 kΩ.
( 4.5 - 0.45 ) / 4700 = 8.617 mA < Sink current.
The maximum bus capacitance of the value Rp limits is approximately 400 pf (capacitive load), calculated by cut-off frequency (1/2 * pi * Rp * Cb), to meet the requirement that the maximum tr (SCL/SDA rising time) is 300 ns.
| Products: | Microcontrollers ,Arm Cortex-M0 MCUs ,M051 Base Series ,M0518 Series ,Mini51 Base Series ,Nano100/102 Base Series ,Nano110/112 LCD Series ,Nano120 USB Series ,Nano130 Advanced Series ,NUC029 Series ,NUC100/200 Advanced Series ,NUC120/122/123/220 USB Series ,NUC130/230 CAN Series ,NUC131/NUC1311 CAN Series ,NUC140/240 Connectivity Series ,Arm Cortex-M4 MCUs ,M451 Base Series ,M451M Series ,M452 USB Series ,M453 CAN Series ,NUC442/472 Series ,NUC505 Series |
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| Applications: | |
| Function: | Peripherals,Connectivity,I2C,Software and Tools,Hardware,Layout |