TCA9548A: Question on the rise time of I2C and pull up resistor

Matthew Chen

Part Number: TCA9548A

Hi team,

For the TCA9548

1. Is there any impact if the rise time of I2C is higher than the datasheet? (pull up voltage 3.3V, frequency 400kHz, I2C rise time 390ns)

2. Is there any impact if the pull up resistor of SDA and SCL is smaller than the datasheet? (pull up voltage 3.3V, frequency 400kHz, pull up resistor 600 ohm)

Thanks a lot.

Matthew Chen

over 3 years ago

+1 Clemens Ladisch over 3 years ago

Guru 317550 points

The I²C specification limits the rise time in order to guarantee that the desired frequencies can be reached. Higher rise times are possible if all devices work with them.

Smaller pull-up resistors also increase the current, and thus the V_OL.

See I2C Bus Pullup Resistor Calculation.

0 Matthew Chen over 3 years ago in reply to Clemens Ladisch

TI__Intellectual 1420 points

Hi Clemens,

Thank you.

Matthew Chen

Interface

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TCA9548A: Question on the rise time of I2C and pull up resistor