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?

Answer: Regarding the question, does it mean that you want to connect the DGND to a separate potential?
For example:
VCC: 80V~, 120V~
VEE: -80V~, -5V~
Intermediate potential:
0V~ (Calculation: 80V + (-80V)/2)
57.5V~ (Calculation: 120V + (-5V)/2)

The DGND will be connected to intermediate potential(0V or 57.5V according to example) (voltage values is changing due to VCC and VEE fluctuates constantly).
Is this what you want to confirm?

If you would connect it to the intermediate potential, the input values for RADJ, TMP and SD will also change according to the voltage of the intermediate potential.
Our recommendation is to connect it to 0V digital ground or analog ground. The DGND pin is reference for all low voltage pins of the amplifier (RADJ, TMP, and SD) and serves as a signal ground for communication to a microprocessor or other low voltage logic circuit.

Q2: To what potential should EXPAD be connected?

Answer: As per datasheet, the function of EXPAD is to improve the heat dissipation of the IC and it should be connected to 0V ground plane, regardless of VCC or VEE voltages. (P. 19 / 21)

As I have written many times, I would like to use the ADHV4702 in the AN1593 circuit.

However, in this circuit, VEE fluctuates according to the output voltage, and VEE may exceed 0V.

If it is connected to a GND plane with DGND=0V, VEE>DGND.

Please access the person who wrote the article of AN1593 properly and check the connection (schematic) of DGND and EXPAD in this experiment.

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

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