On the L6562A with VCC=12V, there is a enable threshold voltage of typically 0.45V on the INV pin. On a flyback design, there is a resistor between the COMP pin and the INV pin.
If the INV pin is lower than the reference of 2.5V, the COMP output should be at a upper clamp voltage level of typically 5.7V. The upper clamp voltage level of 5.7V could contribute to increase the voltage on the INV pin and enable the IC without any additional bias.
In order to proper calculate the enable condition, I would need to know what is the COMP output voltage when the IC is disable. The datasheet does not mention what is exactly shut down. On the block diagram, we see the the DIS signal disables the "Driver & Clamp" but this is not clear if the COMP ouput is High-Z or not in this condition.
