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TIDA-010074: TIDA-010074 LM2904B QUERY

Star Xu
Genius 9645 points
Part Number: TIDA-010074
Other Parts Discussed in Thread: LM2904B, , LM2904

HI

The LM2904B in the reference design TIDA-010074, as the 16 or 17 section, the maximum power supply of LM2904B is only 26V, 17 strings voltage is close to 60V. Does the power supply will damage.
Thanks
Star

TIDA-010074

  • Former Member
    0 Former Member

    Hello,

    Could you please specify where the 60V voltage is located?  Are you referring to the "Bat+" node in figure 1?

    It's not immediately clear from just looking at the circuit in figure 2.

    Thanks,

    Daniel Miller

  • Former Member
    0 Former Member in reply to Former Member

    Hi Star,

    Though I do not believe your question has been answered, I have not heard back from you in a while.

    If you need further assistance, please let me know.  Else, I will consider the matter to be resolved.

    Regards,

    Daniel

  • 0 in reply to Former Member
    TI__Genius 9645 points

    Hi Daniel

    Thanks for your reply.

    The VSS of the LM2904 is connected to the MOS. If it's turned on, the supply voltage of LM2904 is 17 series cell voltage applied to the op amp.
    Waiting for your reply.
    Thanks
    Star
  • Former Member
    0 Former Member in reply to Star Xu

    Hi Star,

    I've taken a further look at the problem and think I now understand your question.

    If you go to the page for the TID and scroll down a bit, you will get to a place where you can download the schematic.  Here is the relevant portion of the design.

    So the V- supply of the op amp is not directly connected to ground.  However, I do not know exactly what the operating voltage of the node will be.  It will depend on the operating conditions which will determine the voltage across the drain-source.  I'm not sure what is going on across Q20 either.  It almost looks like they tried to diode connect the transistor. 

    Unfortunately, there are no TINA sim files already built.  If you look in the bottom right of the schematic, you can see the name of the engineer that designed, or at least put into Altium, this project.  I recommend you email him directly to confirm.  I do think that you are right, however, that the supply voltage will be too high if the supplies are Vbat and GND.

    Please let me know if you need any further help.

    Regards,

    Daniel