Question about LTC2946-1 (datasheet 37 page)

datasheet 37 page "6V to 300V High Side Power, Charge and Energy Monitor"

What is the difference between FGND and GND symbol connect to Q3(2N3904)'s EMITTER?

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  • +1
    •  Analog Employees 
    on Mar 18, 2020 4:44 PM

    Greetings swjung,

       FGND is the floating GND node and is ~5V below Vin.  This value is set by the Zener diode (Z1).  This allows the LTC2946 to be powered by 5V while dropping the remaining voltage through the transistors below.  Something else to look into, as a replacement for the transistors and the optocouplers is the ADM3260.

      www.analog.com/.../ADM3260.pdf
     

    Thank you and best regards,

    Brad Lovell

Reply
  • +1
    •  Analog Employees 
    on Mar 18, 2020 4:44 PM

    Greetings swjung,

       FGND is the floating GND node and is ~5V below Vin.  This value is set by the Zener diode (Z1).  This allows the LTC2946 to be powered by 5V while dropping the remaining voltage through the transistors below.  Something else to look into, as a replacement for the transistors and the optocouplers is the ADM3260.

      www.analog.com/.../ADM3260.pdf
     

    Thank you and best regards,

    Brad Lovell

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