Questions about LT6011

Hello Kazu ,

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 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

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