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PCA9306: PCA9306DCTR

pankaj kumawat
Prodigy 10 points
Part Number: PCA9306

I have some doubts in the PCA9306DCTR IC, could you please help me to make it clear

  1. Is there any limit in the resistors value to be used in both side of PCA9306 ?
  2. PCA9306 have pure open-drain outputs ?
  3. Why we need 200K in series to the VREF2 power supply ?

 

  • 0
    TI__Guru 62910 points
    Hi Pankaj,

    There are not restrictions on the pull-up resistor values with respect to the PCA9306. In sizing the resistors, though, you should keep in mind that the PCA9306 introduces only a small series resistance when conducting (i.e., during low bits), and so the I2C device trying to pull the bus low will sink current from the pull-ups on both sides of the translator. If the resistances are too small, then, the device pulling the bus low may not be able to achieve a proper VOL (output low voltage) level.

    The device does not have open-drain outputs. It is designed to work with open-drain outputs by conducting during "low" bits and going high impedance during "high" bits. When the device is conducting, though, it is not pulling the signals to ground. The signals will be pulled to ground by another device through the PCA9306.

    The VREF2 terminal is not a power supply input; rather, it is a reference voltage used in creating an internal bias voltage for the switching FETs. The series resistance is needed to limit current flowing into this circuit.

    Please let us know if you have any further questions.

    Regards,
    Max