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ISOS141-SEP: Enable Low voltage

Part Number: ISOS141-SEP

I’ll have two pieces of HW that will use 4 of the isolator chips each. The two pieces of HW are in separate housings for redundancy. I’ll need to connect each of the 3 equal direction outputs from one housing with the 3 equal direction outputs from the other housing. This connection is external to the housings. The operational mode is that only one piece of HW is powered while the other one is off. This means I need to have a cheat power connection via diodes from one housing to the other (looks feasible at this point), so I can keep all drivers on without powering the rest of the switched off HW. Then the OFF-HW isolators will need to be held in TRI-State (EN pulled low).


I would like to know if there is data that shows the maximum Enable  Low voltage. If it can be held low sufficiently with w simple PNP bipolar transistor whose base is connected to GND via base resistor of e.g. 1K – is that sufficient with the internal 2M pull up and 1.9K series resistor to keep the outputs in Tri-state?

  • Hi Steve,

    Thanks for reaching out.

    The recommended maximum low input voltage (VIL(max)) is 30% of its supply voltage, VCC, i.e., 0.3*VCC. If VCC = 5V, then VIL(max) = 1.5V. Any applied voltage to the enable pin less than 1.5V for 5V supply is guaranteed to be considered LOW, as stated in the datasheet. Hence, connecting a PNP with 1kΩ base resistor to GND should do the job. I do not see any issues with this approach.

    Let me know if you have any questions, thanks.

    Koteshwar Rao