In the schematic attached there is the power section of my board. On the left there is +12VDC, IC1 provides the +3.3V for MCU. IC2 provides about 5.5V and IC3 generates the negative rail (-5.5V).
It works fine, but there is an issue... if the input voltage rises too slow it seems the ADM660 doesn't start to oscillate (the output is 0V) and sinks a lot of current (over 300 mA).
I mean, if I enable the output from a bench power supply, it's very likely it doesn't work. Instead if I plug-in the connector with the bench power supply already enabled it always works.
The Vee is connected only to a low-power op-amp (few mA) but I tried to change this with several models and nothing changes, so I assume the problem is just related to the ADM660.
Do you see something wrong in my schematic?
I could put a zener diode in series with the input, in order to increase the lowest voltage to feed the regulators... but I would like to understand where is my fault!
I also tried to connect LV to GND - with no chance.