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LM5106 symmetrical power supply

BB_Axign
Prodigy 40 points
Other Parts Discussed in Thread: LM5106

We would like to use the LM5106 in a Class-D power abplifier, but I was wondering if it is possible to use it with a symmetrical power supply.

Or in other words, with a negative voltage reference on the half bridge.

According to the datasheet Vss is the reference of this device, but it's not completely clear if that could be any type of voltage (including negative voltages)

  • 0
    TI__Intellectual 2910 points

    BB_Axign,

    Thank you for your interest in LM5106. This devices has a single ground, VSS. The control input pins are referenced to this ground.

    Although you could make VSS negative with respect to your system ground and VIN to the half-bridge being positive (as long as the specs with respect to VSS are met), your design would have to ensure that IN, EN, RDT, and VDD meet spec with respect to VSS. For example, if VSS = -20V, then the absolute max voltage on the VDD pin would be -2V.

    I can consult with my colleagues to find a recommendation for your design with a dedicated input ground that allows split supply. Can you share more details -- supply voltages, gate drive strength, etc.?

    - Daniel

  • 0 in reply to Daniel Ruiz
    Prodigy 40 points

    Daniel,

    Thanks for your response.

    To answer your question, I am going to give a very practical answer.

    The LM5106 is going to be used in a Class-D amplifier, with symmetrical voltage rails of ±40-80V. Power: 300-1000W

    (in other words, we consider multiple design possibilities)

    The PWM outputs have a maximum of 3.3V with a ground reference. I assume a level shifter is needed to 'convert' the ground (0 volt) reference to the negative voltage rail as reference?
    Gate drive strength is a little less important, because gate drive buffers can be used.

    Hopefully this give you enough information.

  • 0 in reply to BB_Axign
    TI__Intellectual 2910 points

    Thanks for the additional information. 

    Regarding the inputs: yes, a level shifter or digital isolator would be needed to translate the signals from 0-3.3V with respect to system ground to signals that are referenced to VSS. Note that the VDD supply also needs to be referenced to VSS.

    Please give me about a day or so to look into alternatives for this type of application with the parameters you provided.

  • 0 in reply to Daniel Ruiz
    Prodigy 40 points
    Thanks a lot.

    I was wondering what your alternatives are by now.
  • 0 in reply to BB_Axign
    TI__Intellectual 2910 points

    Going through our catalog and discussing with my colleagues, at this point we do not offer a gate driver in this voltage space that provides what you are looking for in a single IC. 

    The option we discussed above of using the LM5106 and level-shifting the inputs and generating a VDD bias supply that is referenced to VSS is one approach. Note that the HS pin recommended max is 100V with respect to VSS. Thus, a symmetrical supply could not exceed +/-50V.

    - Daniel