ADUM347* Vreg Voltage

We are developing a +-15 volt supply around the ADUM3473, but have a questions regarding the Vreg voltage.  If we configure the voltage divider resistors to a Viso voltage of 16 to provide sufficient headroom for downstream 15 volt LDOs, would this be too far outside the Vreg range of operation for long term use?  If so, would the ADUM3473 function properly by supplying either the VDD2 pin or Vreg pin with regulated 15 volts from the downstream 15 volt LDO supplied by the 16 volt Viso output?  Which would be preferable, supplying the VDD2 directly or just the Vreg pin? Can the Vreg pin be left floating if unused?

Thanks for your help.

  • 0
    •  Analog Employees 
    on May 9, 2018 10:43 PM


    The best way would be to connect the 15V regulator output to the VREG pin to ensure this pin does not go too high.  The VDD2 pin max output is 5.7V so it should not be connected to 15V.  The VREG could only be left floating if the VDD2 pin is connected to an external 5V or 3.3V supply needed to power the internal circuits of side 2 of the ADuM347x.

    Regards, Brian

  • Thanks so much for clarifying.  One last question, what current consumption might we expect from Vreg and VDD2 in the 25 mbps configuration?  We are trying to size a regulator to supply the Vreg pin.

    Thanks again for your help.