Are there any issues I need to consider if I choose to connect the VAdj to a DAC to control the Isolated supply?
The Vadj pin will control the duty cycle of the PWM control of the Viso output voltage. For a given load, increasing the duty cycle will increase the output voltage. Typically Vadj is used with an upper and lower resistor as shown in figure 14 and 25 of the datasheet. If you use a DAC to control Vadj the voltage on the Vadj pin will control the duty cycle. Internally, there is a voltage divider from VDD to Vadj to GND1, therefore the Vadj voltage applied will need to be less than the 5V of VDD. Increasing the Vadj voltage will reduce the duty cycle to a minimum, reducing Vadj will increase the duty cycle to a maximum.