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THS7530: Driving the Gain Setting Input In Double Ended supply

Youssef Boulaknadal
Prodigy 30 points
Part Number: THS7530


I would like to use this part the Vcom at 0V. I'm using a +/-2V power supply. 

What will be the VG- Referenced to? Will the voltage range still be 0 to 0.9V in this case?

Thank you,

  • 0
    TI__Genius 15565 points

    Hello Youssef,

    Using a +/- 2V power supply, you will be under the minimum supply voltage needed to power the device (This is 4.5V). Under "gain control" on page 6, the VG- pin is shown to reference the negative supply, and has a range of -0.6 to 0.8V. This will not change the voltage range of 0 to 0.9V between VG+ and VG-. Hope this helps!

    Best,
    Hasan Babiker

  • 0 in reply to Hasan Babiker31
    Prodigy 30 points

    Hello Hasan,

    Thank you for your quick answer. 

    I'm actually using +/-2.5V power, sorry for the confusion. 

    I was using the simulation to test for this configuration and noticed that there is dip in the output profile with a minimum at -0.454. Do you know what may causing this? Does the range of control voltage supposed to be > >-0.300V


    Thank you,

     

  • 0 in reply to Youssef Boulaknadal
    TI__Genius 15565 points
    Hello Youssef,

    The gain control of this model is a simplified version of the control on the part itself. Notice that the model does not include both VG- and VG+. Think of the model pin as VG+, with VG- set internally to Vs-. That dip is a result of the device exceeding the differential voltage range of 0V-1V, or in other words the gain control pin should not be set outside the range of -2.5V-1.5V when Vs- = -2.5V.

    Best,
    Hasan Babiker
  • 0 in reply to Hasan Babiker31
    Prodigy 30 points

    Can I drive this device with a DAC that has a single positive supply, by making the positive output to VG- and GND to VG+. I other words, is the input fully differential or I need an isolated supply to drive the gain control?

    Thank you,

    Youssef

  • 0 in reply to Youssef Boulaknadal
    TI__Genius 15565 points
    Hello Youssef,

    To use a single supply for your gain control, you would want to tie VG- to Vs- and control VG+ using your DAC.

    Best,
    Hasan Babiker