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TPSI3050-Q1: Is it possible to power an AMC1311 high side with the Iaux power output?

Nathaniel Woods
Prodigy 20 points
Part Number: TPSI3050-Q1
Other Parts Discussed in Thread: AMC1311, TPSI3050,

Hello,

We are working on a board with a 400V power input. We have an isolated 5V section to power our MCU and a few other LV Circuits. We need to monitor the voltage of our supply, which we are planning to do with the AMC1311DWVR. The original plan was to use the SN6501DBVR transformer driver to create the isolated 5V supply. However looking at the datasheet for the TPSI3050 isolated gate driver it looks like it might be possible to use the VDDM to power the high side supply.  There are two main complications that I can see. First, The second issue is I am not sure the auxiliary supply is going to be an adequate power source for a sensitive voltage monitor. Second, the TPSI3050 is floating VDDM (and VDDH) above the 400V supply to drive high side N-channel MOSFETs meaning that if we followed the recommended voltage divider configuration in the AMC1311 datasheet we would have a potential difference of ~400V. I was thinking this could be solved by switching the 20.5k sense resistor and the 3.9MOhms of series resistance such that there is only a small voltage difference between the the sense resistor and the AMC1311.  Can you please weigh in on this?

Best,

Nathaniel

  • 0
    TI__Expert 5576 points

    Hello Nathaniel,

    Thanks for reaching out to our team! 

    1. Nathaniel Woods said:
      The second issue is I am not sure the auxiliary supply is going to be an adequate power source for a sensitive voltage monitor.

    Looking at the AMC1331 datasheet, it looks like the maximum input current spec is 9.7-mA.The maximum current we can supply from VDDM is 10-mA so this is fine. Next, let's check the maximum switching frequency we can support given a 9.7-mA auxiliary current. I'm unsure which MOSFET(s) has been selected so I'll take the UF3C065030K3S as an example here and input the settings into our Calculation Tool (SLVRBI9) to check.

    Qg = 30 nC


    Inputting into the calculation tool:

  • Think I understand what you described, drawing out a quick schematic to confirm.

    • Best regards,
    Tilden Chen

    Solid State Relays | Applications Engineer

  • 0
    TI__Expert 5576 points

    Hang on, was still typing a response and then the text editor crashed on me so I clicked reply. Still need to edit it for full response

  • 0
    Prodigy 20 points

    My circuit looks more like this. With the capacitors in the spots you had them.

  • 0
    TI__Expert 5576 points

    Hello Nathaniel,

    Thanks for the quick reply. I was mistaken in thinking the TPSI3050-Q1 was switching for the HV measurement. It looks like the load is separate. In this case, if you already have a MOSFET selected, you can follow the same steps I outlined in my first reply to check if the resulting maximum switching frequency is sufficient for your application.

    Perhaps also double check with the amplifiers team to see if AMC device can be placed on the high-side, but the TPSI305x-Q1 will have no problem on the high-side: VDRV = VSSS + 10-V. 

    If I'm understanding your schematic right, your initial concern was with placing the 3.9M before the 20.5k like this:

    That looks like it should work too. VDDM = VSSS + 5-V. The MOSFET gates will see VSSS + 10-V when driven.

    Best regards,
    Tilden Chen

    Solid State Relays | Applications Engineer