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P82B96: P82B96 with TCA9416

Phillip Karls
Prodigy 80 points

Part Number: P82B96
Other Parts Discussed in Thread: TCA9416, , TCA9803, TCA9517, TCA9509

Will I run into any issues using the P82B96 with the TCA9416 in a setup like this:

image.png

 

The TCA9416 is a "switch type" voltage translator, so I believe it will be fine, but I would appreciate a second look.

 

  • 0
    TI__Guru 61278 points

    Hi Phillip,

    P82B96 is VIT input threshold is independent of the supply voltage. 

    A 3.3V supply from the TCA9416 should allow the P82B96 to work properly even though a 3.3V input is being applied instead of 5V. 

    The problem with this setup is actually when driving a logic low from the remote control enclosure side. The output voltage of Sx,Sy terminals is max of 1V. This means the MCU will see approx vol = 1 V which the MCU is based off 1.8V. I think you would need some type of buffer in place of the TCA9416. 

    Can you opt for using TCA9803 with B-side facing the MCU, and A-side facing the P82B96? 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 80 points

    Hi Tyler,

    Thanks for the answer. Good catch on the Vol from the P82B96.

    The MCU is a SOM that has integrated I2C pull ups, so I can't use it with the B side facing the MCU.

    Regardless, wouldn't this solution have the same issue with Vol of the P82B96 being potentially greater than the Vil of the TCA9803:

     

  • 0 in reply to Phillip Karls
    TI__Guru 61278 points

    Hi Phillip,

    The VOL of P82B96: 

    Technically a max of 1 V, if you adjust the pull-up resistors to sink 3 mA. VILA for TCA9803 = 0.3 x VCCA = 0.99V max. There is technically 0.01 V outside spec if looking at the max. 

    If you adjust the pull-up resistors on Sx/Sy side to 0.2 mA, your max drops to 0.79V, which fits within the spec of the TCA9803. 

    Your B-side output voltage of the TCA9803 that faces the MCU is:

    This is much lower than the P82B96. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 80 points

    Hi Tyler, 

    Could I just add a TCA9517 inbetween the P82B96 and the 3.3V I2C bus to solve this issue?

    (A side of TCA9517 on 3.3V side, B side on 5V side)

    Thanks,

    Phillip

  • 0 in reply to Phillip Karls
    TI__Guru 61278 points

    Hi Phillip,

    The B-side input of TCA9517 is 400mV, so the large offset from P82B96 would be incompatible. 

    What about using TCA9509 in place of TCA9416? 

    The low-side input is now on 1.8V side. TCA9509 integrates a 1mA pull-up current source. Pull-up resistance is not needed on the MCU side. 

    B-side of TCA9509 would be compatible to P82B96 as long as the sink current is low enough. VILB = 0.3 x 3.3V = 0.99V for TCA9509. 

    A-side TCA9509 VILC = VILA = ~150mV. 

    Regards,

    Tyler