Questions about LT6011

Question

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

PaulCA · Accepted Answer

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

ZoltanDTI · Answer

Hi Kazu , 
 In addition to what PaulCA 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

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