Post Go back to editing

ADG734 and digital input levels with VSS < 0

Hello everyone, I have a question related to ADG734. In a certain application, there is a need to switch between different signal lines that are at a negative voltage around -0.7 to -0.2 V. For that reason, an ADG734 IC used with VDD=+3.3 V and VSS=-1.2 V (and not 0 V). The digital input lines that control the four SPDT switches inside the IC are connected to GPIO pins of another system and swing between +3.3 V and 0 V.

The datasheet of ADG734 states that, with VDD=3 V and VSS=0 V, the input low voltage (VINL) is 0.8 V maximum. Is it right to assume that, for VSS=-1.2 V, VINL=VSS+0.8 V = -0.4 V maximum? If yes, then having the digital input signal that controls the switches at 0 V should NOT be OK and some sort of level shifting, e.g. using a MOSFET switch with VSS=-1.2 V should be used. Is my assumption correct? Please advise.

Parents
  • Hi,

    No, your assumption is not correct.

    The digital logic circuitry is powered only by VDD.

    So, the value of VSS should have no impact on the VINL specification.

    Regards,

    David

  • Hi George,

    I would have to agree with David Forde in this case.

    If unsure about the VINL and VINH voltage levels of the ADG734 device, reference the dual supply voltage specification table (+/- 2.5V) as a reference for these voltage values for a dual supply voltage range. 

    Would you have a schematic or application specific circuit that you could share to help understand how the negative voltages (-0.7V - -0.2V) are switched between different signal lines in your certain application ?

    Regards,

    Kevin

Reply
  • Hi George,

    I would have to agree with David Forde in this case.

    If unsure about the VINL and VINH voltage levels of the ADG734 device, reference the dual supply voltage specification table (+/- 2.5V) as a reference for these voltage values for a dual supply voltage range. 

    Would you have a schematic or application specific circuit that you could share to help understand how the negative voltages (-0.7V - -0.2V) are switched between different signal lines in your certain application ?

    Regards,

    Kevin

Children
No Data