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TCA9548A: Slave Bus Voltage 1.8V and Master with 5V

Marks Greulich
Intellectual 530 points
Part Number: TCA9548A
Other Parts Discussed in Thread: TCA9546A

Hi guys,

I want to split up a 5V I2C coming from an Atmega controller into 3 independent I2C-Busses with 1.8V logic. 

I have pretty high ambient temperature - max. of 125°C so ofcourse it is at the upper edge. 

So I have to take a lower Vcc (thermal reasons) and also less then 2.5V cause of Vpass <=1.8V. 

My question: Is it ok using Vcc=1.8V to meet my requirements of Vbus (Slaves) 1.8V logic?

2nd question: A0-A2 & Reset: is it fine that I`ll use 5V high and not the recommended "max. Vcc+0.5V" (=2.3V)? If I look to max. abs spec it is allowed up to 7V without damages. 

Thanks & regards,
Markus

  • 0
    TI__Mastermind 22615 points

    Markus,

    Thanks for reaching out!

    Marks Greulich said:

    My question: Is it ok using Vcc=1.8V to meet my requirements of Vbus (Slaves) 1.8V logic?

    I think 1.8 V should work, but you must make sure that your VOL from the 5V side is below 0.54 V, as this is the low-level input voltage requirement at VCC = 1.8 V.

    Marks Greulich said:

    2nd question: A0-A2 & Reset: is it fine that I`ll use 5V high and not the recommended "max. Vcc+0.5V" (=2.3V)? If I look to max. abs spec it is allowed up to 7V without damages.

    When you exceed the recommended operating conditions, you might not get perfect functionality. This condition is different from the others because it uses different circuitry (see section 8.2 of the datasheet).

    Marks Greulich said:

    I want to split up a 5V I2C coming from an Atmega controller into 3 independent I2C-Busses with 1.8V logic.

    You are looking to only use 3 channels? The TCA9548A is an 8-channel device. Have you looked at the TCA9546A? You can also find our portfolio of different I2C switches and multiplexers here.

    Best,

    Danny