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Questions about LT6011

Category: Datasheet/Specs
Product Number: LT6011IS8

Hi,

I am operating LT6011 with supply voltage V+=1.8V, V-=-1.8V. Due to a situation on the power supply side, V+=1.8V is cut off (V+=OPEN) during standby.

Also, there is no input at standby. At standby: V+=OPEN, V-=-1.8V, Input: +IN=-IN=0V

Is there any problem with this kind of usage (V+=OPEN)?

Regards,

Kazu

Top Replies

  • Hello  ,

    Just a few clarifications, what do you mean by V+=OPEN? Does it mean the V+ supply pin is not connected to anything? or the V+ supply is connected to a voltage supply with no voltage configured (Ex. 0V/GND)?

    In addition, during standby, are the op amp's inputs floating (don't have connections)? 

    Regards,
    Paul

  • Hi Paul,

    The standby state is as follows.

    The V+ pin is not connected to anywhere. The V+=1.8V line is turned off by a MOSFET switch.

    The op amp's inputs are 0V, not floating.

    Regards,

    Kazu

  • Hi,

    This may not damage the opamp as long as correct power sequencing is followed:

    • During the Power On sequence, turn on the supply first, then apply a signal at the input 
    • During the Power Off, turn off the input signal first, then turn off the power supply 

    One problem that I can see from this is that the opamp will not work as it intended to be during standby. The negative voltage from V- pin can pass through the V+ and Output pin. See simulation below: 

    V(n001) = V+ Supply Voltage

    V(n002) = Output Voltage

    If the V+ pin and Output pin are connected to terminals of other chips that haven't been fully powered, those chips may suffer damage.

    For more information regarding this topic, please see: Improper Power Sequencing in Op Amps: Analyzing the Risks | Analog Devices

    I hope this helps. Thanks.

    Regards,

    Paul

  • Hi  ,

    In addition to what   said, I think it is not a good idea to use the opamp out of what is specified even is the maximum ratings seem to be met. Do not let the supply pin V+ float. Although I don't know why do you want to switch off the positive supply, find another solution that fits to your needs.

    And yes, be careful with power supply sequencing.

    Zoltan