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Category: Hardware
Product Number: ADUM1250ARZ

Hello experts,

We want to use the ADUM1250 I2C isolator in our design. The system is having the two ground references GND1 and GND2 and single power supply of 3.3v VDD. Can i connect the VDD1 and VDD2 of the ADUM1250 to a common power supply of 3.3V. However the GND1 of the ADUM1250 is connected to the GND1 of the system and the GND2 of it is connected to the GND2 of the system. 

  • Hello Hussaini,

      This configuration may be possible, but typically this would not be a suggested topology.  Without knowing more details regarding the schematic and physical system layout, etc. this is a hard question to definitively answer.

     For this topology to potentially work, two conditions would need to be met. 

      First, the supplies for both sides need to have an external closed current path between the side's VDDx and GNDx  This means that assuming a use case with a single common 3.3V VDD net and two separate GNDs, one for each side, there will ultimately need to be an electrical connection between GND1 and GND2 someplace within the system (and both GND's need connect to the 3.3V supply's reference).

       Next, any variations between the 3.3V net and GND1 or GND2 will need to remain within the recommended operating range for the ADuM1250 (3-5.5V) and definitely not exceed the ABSMAX of 7V.

      If the above conditions aren't met, then adding an isolated supply to generate a 3.3V supply referenced to GND2 (assuming the existing 3.3V supply is referenced to GND1) would be needed.

      Generally, its best to have the supply and I2C bus for one side share the same local supply and return/reference as the other parts on that side's I2C bus.  Depending on the system and its physical construction (layout), this may appear in the schematic that both sides share the same electrical net, but due to the parasitic components of the physical layout they really are different nets/nodes.