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TCA9801: Used for I2C Isolation

Sushruta Shetty
Intellectual 655 points
Part Number: TCA9801


Hi Team, 

We are using TCA9801DGK in one of our new design for i2c isolation when the slave is not powered on. 

Please find the below image for more details.

1.Power Switch and TCA9801 IC will be disabled in default condition, and shall be enabled only by MCU
2.When enabled, VOUT_3V3 shall be supplied to the slave device after some delay configured by CT pin of the Power switch
3.I2C _A SCL and SDA lines are connected to 4.7K pull up. Pull up is not provided at I2C_b side owing to the current source configuration
4. Is there an issue if enable voltage comes before VCCB is supplied(note that VCCA is available always)
5. Whether delay circuit( RC delay)is required to enable I2C isolator .
Let us know if any concern or suggestions.

Regards,

Sushruta

  • 0
    TI__Guru 53575 points

    Hi Sushruta,

    If the the device is enabled at the EN pins while VCCB is below UVLO, all SDA/SCL pin on both sides will be high impedance. The B-side current source will be disabled and a weak pull-up will keep the B lines from floating. Once VCCB raises to acceptable levels, the device will be able to function normally. Similarly, if VCCB is brought high before EN, the device will remain high-z until EN is brought up. 

    No delay is necessary for the enable pin in these cases.

    Regards,

    Eric