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Original question:

ISO 124

INA271: Highside sensing for HV power supply

Daniel Kissenkoetter
Prodigy 30 points
Part Number: INA271
Other Parts Discussed in Thread: ISO124

Tool/software:

simulation does work.

what do you think about that?

  • 0
    TI__Mastermind 32395 points

    Hey Daniel,

    Thank you for your post.

    The INA271 can theoretically be floated, but your schematic is unclear about one thing: How is GND2 (or GREF1 in the simulation) connected to the load ground? 

    You can never violate the following ratings:

    1. Voltage from input pins (IN+ and IN-) to device GND (Vcm) must remain >= -16V and <=80V

    2. Voltage from supply pin (V+) to device GND (Vs) must remain >= 2.7V and <=16V

    In your simulation, V_IN+  is 30kV with respect to load, thus GREF1 must always be <=30.016 kV or >= 29.02 kV.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    Prodigy 30 points

    Hey Peter,

    Does GND2 need to be connected to HV-GND?

  • 0 in reply to Daniel Kissenkoetter
    TI__Mastermind 32395 points

    Hey Daniel,

    GND2 I believe should be your high voltage ground according to schematic. Although this means your Vcm is now 30kV which will not work for INA271. If this is case then you would need to put INA271 on the low side (below R4).

    Although to better answer your question I will add the expert in isolation to assist.

    Overall you still must maintain the following inout pin voltage ratings I described in last post.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    Prodigy 30 points

    Hey Peter,

    I have another schematic. GND2 comes only from the DC-DC converter and is not connected to the ground of my high-voltage power supply

  • 0 in reply to Daniel Kissenkoetter
    TI__Mastermind 32395 points

    Hey Daniel,

    Do you know if there is any definitive voltage difference or connection between GND-HV Power Supply (or the 25kV rail) and GND2? This is the crux of issue for INA271. I will defer to the ISO124 expert on the ISO124 schematic and ground connections, but overall, the Vcm of INA271 cannot be violated as I have mentioned. So you need to define what is the voltage difference between IN+ (25kV rail) and GND pin (GND2 net).

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    TI__Guru 55322 points

    Hi Daniel,

    The ISO124 will not be able to withstand 30kV for long, only rated for a min of 1.5kVAC. It also required bipolar power supplies on both high and low side which I cannot confirm from your schematic if they are present. 

    Can you please comment on what is driving the desire for high side current sensing on a 30kV application?