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LM5056: Using for -48V system

K. Sasaki14
Guru 10200 points

Part Number: LM5056
Other Parts Discussed in Thread: INA226, TIDA-00313

Can we use LM5056 for -48V power line monitoring?
I think it is possible if -48V line is connected as GND and GND line is connected Vin.
Is this idea correct?

If this is possible and you have reference schematic for -48V system, please share with me.

Best Regards,
Kohei Sasaki

  • 0
    TI__Genius 15770 points
    Hi Kohei,

    We have not analyze the LM5056 for -48V applications. Why are you considering this device? You need PMBUS communication or it's I2C communication acceptable? I am asking because I designed a TI design for -48V applications using the INA226 device (Digital Output Current Shunt Monitor with I2C).

    You can find the TI design in the following link:
    TIDA-00313 - -48V Telecom Current/Voltage/Power Sense with Isolation
    www.ti.com/.../TIDA-00313

    Regards
  • 0 in reply to Mayrim Verdejo
    Guru 10200 points

    Mayrim-san,

    Tnak you for your information.
    PMBus is not needed, however digital interface is needed. So I2C is OK.
    I reached LM5056 because I couldn't find the device that allows 48V input.

    I checked TIDA-00313, I think this is good. Thus I will suggest to our customer this solution.

    Best Regards,
    Kohei Sasaki

  • 0 in reply to K. Sasaki14
    TI__Intellectual 1906 points

    Hi Mayrim,

    my customer is using the LM5056 with -48 Volt and facing the issue that sensing the RTN is very noisy and therefore a solution would be to run a low side sensing with the device.  Question therefore will be if the VIN_K is not somehow linked to VIN.  This would means Sense would go to GND and and VIN_K would measure GND+drop. Would the sense amplifier work in that area? 

    I tried to get the customer to the INA226 but this would require a SW change which he can not run (too late in the Design process).

    best regards, Bertram

  • 0 in reply to Bertram Brummer
    TI__Genius 14825 points
    Bertram,

    Without a schematic it's a little unclear to me the configuration of the device, but I'm guessing that when you say it's low-side sensing, you're connecting VIN or VIN_K to some value very close to the negative rail the part is also connected to. Does this mean that VIN, VIN_K, or SENSE will be below 10V? That violates the recommended operating conditions of the data sheet. It doesn't violate the abs max, but it should be noted as performance may vary. Also, VIN to VIN_K has an abs max of -0.3 to 0.3V apart from each other. Would this design violate that criteria?