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TCA9617A: pull A port in 1V when DC off stage

user4979899
Expert 3080 points

Part Number: TCA9617A
Other Parts Discussed in Thread: TCA9517A, TCA9617B

Hi Sir,

Below is the schematic of TCA9617A which using to replace competitor PCA9617.
We found TCA9617 will pull low port A to 1V when DC off stage. (DC off stage means P3V3_STBY have power and P3V3 no power)
After DC on, we see port A pull to 3.3V, it is correct.
And then we DC off, we see port A keep at 3.3V.
We can’t read I2C address and it only occur at AC power on, TCA9617A will pull port A down to 1V.

Below is the waveform we captured.

Thanks

  • 0
    TI__Guru 62920 points

    Hi Anne,

    In the TCA9517A datasheet it says that VCCB must be powered up prior to VCCA and that if SDA/SCL are pulled up before VCCB is powered then there could be significant leakage currents into those pins.  It seems like that is what is happening here, and the additional leakage current is resulting in the bus lines to remain at this lower voltage.  Assuming that is the case, moving to the TCA9617B device seems like a simple solution.  It is p2p with TCA9517A but features high-impedance IOs when not fully powered.

    Regards,
    Max