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SN74CB3Q3257: Is SN74CB3Q3257 suitable in i2c interface?

Part Number: SN74CB3Q3257

Dear E2E,

Is SN74CB3Q3257 suitable in i2c interface?

Anything we sould pay attention when we design SN74CB3Q3257 in system?



  • Jason,

    The SN74CB3Q3257 should suit your needs for I2C support. Make sure you follow the appropriate specifications for the I2C data rate in which you are running at:

    Given that the switch has a low and flat on-resistance as well as low on-capacitance: 4Ω and 10.5pF respectively. This should help with the rise time and capacitive loading for each bus line: SDA and SCL.

    Keep in mind that each slave device added to a bus will increase the capacitive loading of that bus due to parasitics to GND. You can estimate about 10pF per slave device added. This will increase your RC constant and in turn increase the rise time.

    Also keep in mind the calculation for your pull-up resistors. Making a resistor too large will make the rise time large, and the signals on the SDA/SCL lines may not have enough time to reach their HIGH state. Make the resistor too small, and SDA/SCL line will have a hard time being driven to an output low-level voltage. If you need more info on calculating pull-ups, check out this application note!

    Hope this helps!