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TCA9548A-Q1: interfacing the I2C to 3x LP8866S-Q1

Dan Tooth
Mastermind 21745 points
Part Number: TCA9548A-Q1
Other Parts Discussed in Thread: LP8866S-Q1, , TCA9517-Q1, TCA9517, TCA39306-Q1

Tool/software:

Hi

Valeo has got one I2C bus and they want to connect 3x LP8866S-Q to it.

Unfortunately, LP8866S-Q1 can only be configured for two possible I2C addresses; 0x2A and 0x2B.

Looking for an automotive grade solution to solve this at lowest cost.

I see the TCA9548A-Q1, but this is over-spec'd with up to 8x I2C outputs.

I was also wondering if we can make use of the Enable pin on TCA9517-Q1 and use 2x of them.

We would connect the first LP8866S directly to the I2C bus and use address 0x2A

The second and third LP8866S would connect to the I2C bus each via its own TCA9517 and would each use address 0x2B. Which one of these two we communicate with is determined by if its TCA9517 is enabled or not.

This method does involve extra two pins on the host to control the two enable pins of the two TCA9157.

Does the above method work?

Is there another / better way?

Regards Dan

  • 0
    TI__Mastermind 48988 points

    Hi Dan,

    I think MUX teams portfolio only has the 8-channel in automotive grade (TCA9548A-Q1) i2c controlled switch. 

    I don't think 2 x TCA9517-Q1 would work. LP8866S-Q1 VIL logic input to SDA/SCL is 0.4 V max. TCA9517-Q1 B-side output voltage is ~0.53V. The VOLB of the buffer cannot be recognized by the LP8866S-Q1. We can't flip the output sides of the TCA9517-Q1 either because then B-side would be connected in parallel to another B-side of the TCA9517 which also is not allowed. 

    An alternative and cheaper method for Valeo would be to use same parallel technique but use TCA39306-Q1 in the switch mode. 

    Dan Tooth said:

    We would connect the first LP8866S directly to the I2C bus and use address 0x2A

    The second and third LP8866S would connect to the I2C bus each via its own TCA9517 and would each use address 0x2B. Which one of these two we communicate with is determined by if its TCA9517 is enabled or not.

    This method does involve extra two pins on the host to control the two enable pins of the two TCA9157.

    This method would work, but replace TCA9517 with TCA39306-Q1. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    TI__Mastermind 21745 points

    thanks Tyler

    Regards Dan

  • 0 in reply to Dan Tooth
    TI__Mastermind 48988 points

    Hi Dan,

    You're welcome! I will close this thread. 

    Regards,

    Tyler