TCA9517-Q1: Pull up resistor selection

ahmet kudak

Part Number: TCA9517-Q1

Tool/software:

Hello everyone,

I need to calculate the pull-up resistor value for an I2C bus, but this bus is about 1 meter from my main board. I need to consider the cable length in that case. Does anyone know how to calculate it?

Best regards

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316690 points

This depends on the cable capacitance, which is hard to estimate if it is not specified.

Just size the pull-ups for a current of 3 mA, and check the waveforms with an oscilloscope. If the clock pulses do not reach or stay at V_CC long enough, you have to reduce the speed.