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AMC1350: Schematic design check

Eric Lai
Expert 4940 points
Part Number: AMC1350
Other Parts Discussed in Thread: ISO224,

Hi Expert,

The engineer would like to design ISO224 plus AMC1350 together.

The user case is 600KW UPS,there will have long distance for signal delivering inside.

The performance look great at AMC1350 output, but we need you to confirm whether this schematic is ok or not?

Thanks

EricISO224 plus AMC1350.docx

  • 0
    TI__Guru 56522 points

    Hi Eric,

    I see that both grounds of the ISO224 and the high side ground of the AMC1350 are tied to the same net. The ISO224 will not provide any isolation, is this intentional for transferring the signal over long distance? Why was ISO224 was selected instead of another device like a non isolated OPA? 

    I recommend 0.22uF for the ISO224 VCAP as shown in the datasheet. What is the purpose of BAS316? Is this another issue with the long distance? The high side supply can withstand the 12V VDD1 voltage directly. 

    Why is RM43, 10k resistor in between VINN and GND1 of the AMC1350? Direct connection is recommended to ensure the input voltage range remains within the common-mode input range. 

    I don't see the OPA schematic as shown in channel 1 on the second picture. Can you please ask for the schematic? 

  • 0 in reply to Alexander Smith
    TI__Expert 4940 points

    Hi Alex,

    The ISO224 solution is selected by engineer. We can propose if better idea had.

    Pls see update:

    APF current sensor test_20230718 update.docx

    The result is great.

     

    The engineer try to short the RM43,but see the distortion.

    Please help to confirm the application problem of AMC1350, if receiving IS0224 differential signal, is it necessary to short-circuit INN to GND1?

    Our concern is that it will cause distortion of the differential signal.

    Thanks

    Eric

  • 0 in reply to Eric Lai
    TI__Guru 56522 points

    Hi Eric,

    Without information from the engineer as to the intended purpose of the current design, I cannot propose a better idea. 

    If the engineer is happy with the results, then I do not see a need to ask them to change. 

    I have a better understanding of why RM43 is present in the design now. The common-mode input range of the AMC1350 is +/-4V, so RM43 is necessary as the ISO224 will output on a common-mode of VDD2/2. Without RM43, the negative output of the ISO224 is directly shorted to GND (SS) which would indeed cause distortion and potentially damage to the ISO224 as the outputs are driven. RM43 = 10k is OK as it will limit the output current and protect the device from damage.