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TCA9534: Question about 5V IO tolerance

Part Number: TCA9534

Hello,

I read some of the posts about TCA9534 in this forum but I still have a question about if I understand the

5V tolerance of IO pins correctly.

I plan to use some TCA9534 in a 1.8V environment. All pins should be used just as outputs to setup different

devices more or less statically. 6 pins drive 1.8 V logic, but 2 pins must be connected to  3.3V and 5V devices.

I'm now not sure if I can mange that with the device. In the datasheet it stated, IO pins are 5V tolerant.

But I have doubts if it is real the case also for outputs. (regarding functional block diagram).

Would it work if the 3.3V and 5V pins are configured as outputs which output value log. LOW and

in case of log. HIGH, if the pins are configured as inputs, provided there is a pull-up to 3.3V and 5V ?

If yes, would it be a save solution ?

Thank you.

  • Hey Robert,

    "But I have doubts if it is real the case also for outputs. (regarding functional block diagram)."

    -I just want to clarify here, the 5V tolerance means the I/O ports can take up to 5V safely without damaging the part (assuming the current into these pins meet datasheet specs.)

    "Would it work if the 3.3V and 5V pins are configured as outputs which output value log. LOW and in case of log. HIGH, if the pins are configured as inputs, provided there is a pull-up to 3.3V and 5V ?"

    -Let's consider the case with 5V as it is larger. When the output is set to low, the FET (tied to GND) will be on and there will be a low impedance path to GND. You will need to have a pull up resistor on the 5V rail to ensure the current into the port does not exceed the recommended (25mA).

    In the case where the output is high, the FET tied to Vcc should be off as the Vgs should be larger than gate voltage (assuming the FET is an NFET) resulting in the FET acting as high impedance.

    If the ports are configured as inputs, there will not be any issues as the input into the device is high impedance.

    "If yes, would it be a save solution ?"
    You should be fine as long as you keep in mind the maximum allowed current when the output is set low and as long as you don't go over 5.5V.

    Thanks,
    -Bobby
  • In reply to Bobby Nguyen:

    Thank you very much for the answer.
    Now I'm pretty calm.
    Best regards
    Robert