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PCA9306: Questions about internal switch

Part Number: PCA9306
Other Parts Discussed in Thread: TCA9406, LSF0102, TXS0102

Dear Team,

I have two questions about PCA9306 as below.

1. I want to know is SW a pure Mosfet in PCA9306? Is there any other control logic in PCA9306 (like one-shot circuit in TCA9406) ?

2. Patrick showed below figure and illustrated the concept of the high bit pass from the host to the slave in another E2E thread. 

    But I have a question that will it has reverse current from 3.3V to 1.8V? Is our switch Hi-Z also when high bit pass?

Thank you.

  • When the I/Os are high, the switch is off, so the voltage is not passed through. (The pull-up resistors are needed to generate the high voltages.)

    As far as I know, the PCA3906 is a relabeled LSF0102; see there for interesting application notes (it's indeed a simple MOSFET). (And the TCA9406 is a TXS0102.)
  • Hey Jim,

    "1. I want to know is SW a pure Mosfet in PCA9306? Is there any other control logic in PCA9306 (like one-shot circuit in TCA9406) ?"

    PCA9306 does use a pass FET architecture to provide level translation. There is other circuitry inside the device (such as ESD structures) but it does not have a one-shot circuit like the TCA9406. 

    "But I have a question that will it has reverse current from 3.3V to 1.8V? Is our switch Hi-Z also when high bit pass?"

    Like Clemens pointed out, the SW in the block diagram will be high impedance. Think of the SW changing from 3.5 ohms to 100 Mega ohms so there will be little current being passed from side 2 to side 1.

    Thanks,

    -Bobby

  • Understood! Thank you team.