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driving i2c address pins

Category: Datasheet/Specs
Product Number: LTC4260

The LTC4260 defines the VADR(H) and VADR(L) but it doesn't define VADR(NC) at all. Could all three states (H, L, NC) be reached using a tri-state gate?

I am using four '4260s to connect an isolated power supply to four different loads. I will have three of these four-channel cards in my system. I would like to use a 'geographical' address bit on the backplane to set the MSB of the address per slot, which would allow me to keep the cards identical. That is, the LSBs would be hard-wired to identical addresses, while a unique, per-slot strap on the backplane would set the MSB to either H, L, or NC.

The problem is that the switch controls must be referenced to the isolated power supply's ground domain. I can cross the ground domain using digital isolators, but I'm not sure how to translate an "NC". If I can detect the NC and use that to control the output enable of a tri-state buffer on the switch domain side, would that work? Would a Hi-Z state be interpreted as an NC?

Thread Notes

  • Hi  ,

    This thread will be transferred to Power Module discussion forums as this is a Datasheet/Specification concern.

    Best Regards,

    Earl

  • Hi PJE,

    In order to couple three states (0, 1, Hi-Z), you'll need two "bits". One way to achieve this is to use e.g. HCPL-2200, opto-coupler that has tri-state enable pin and drive the enable pin with another HCPL-2200 (or other opto-coupler). Alternatively, as the signals are static, you can use cheap transistor output opto-couplers so that the output transistors are stacked (and having a protective series resistor in case that both transistors are conducting).

    Cheers, heke