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LT3094 does not start correctly

Hi,

I am having issues with the start-up of the LT3094 negative LDO. 

The LDO is used to generates -1.8V voltage from a -3.3V voltage, as shown in the schematic below: 

Most of the time, the LDO will start correcly. But from time to time, the LDO output will be stuck at +0.9V and will not go to the desired voltage, -1.8V. After a few power cycles, the LDO will eventually start up correctly. 

After doing some measurement, I noticed that this +0.9V voltage was always present at the LDO output prior to its startup, even when the startup was correct. It looks like this +0.9V comes from another circuit on the board.

Indeed, the LDO is used to give the negative supply to a dual supply opamp. The opamp positive supply is ON before the LT3094 starts up, which makes me think that some current could go from the opamp to the LT3094 output, creating this weird +0.9V voltage. This current was measured at about 30mA (current sinked into the LT3094). 

Can this  +0.9V voltage prevent the LT3094 from start up correctly? What happens on the outputs of the LDO when it is not supplied?

Thank you,

Maxime Puech