application note AN1593 for the ADHV4702

Question

I have a question regarding application note AN1593 for the ADHV4702. 
 Q1: VCC and VEE fluctuate constantly. DGND connection Should I create and connect a VCC-VEE intermediate potential separately?

(With VEE, I am concerned that the maximum absolute rating is VEE to VCC-12V and the margin is 0.) 2: To what potential should EXPAD be connected? 
 Thank you.

jeobico · Accepted Answer

Hi UBOTI san, 
 The author of the article explains that the DGND is only needed as reference for the SD, TMP and RADJ pin same as what we've shown before. 
 Having the DGND connected to ground(0V) will violate the Absolute Maximum Ratings when VEE is greater than 0V as you've pointed out before. 
 With this, we would suggest same as your proposal that DGND be shorted to VEE or connect it to VEE with a resistor to set the DGND value greater than VEE. Since the DGND fluctuates same as VEE, the SD pin should also be connected to VEE and DGND with a switching circuit between pins that will choose to have an active High or active Low status. 
 As for the EXPAD, it is left as floating based on the author, however if there are issues on the heat dissipation, this can be connected to the exposed copper top layer for thermal management if the design is based on the evaluation board. 
 Hope that helps. 
 Regards, 
 JE)

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application note AN1593 for the ADHV4702