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The LTspice model simulation output of ltm8049 is not as expected

Category: Hardware
Product Number: LTM8049
Software Version: LTspice XVII(17.0.35.0)

Hi, when I simulate the output of ltm8049 with LTspice tool, I find that the output was incorrect. Using the demo schematic provided by your company, I just chang the input from 12v to 3.3v. Then observe that Vout_ 1 is only+8.5V and Vout_ 2 output is only -8.0V, both of which are  less than ±12V.  Similarly, pg signal is always at gnd level.

I really don't understand why. How can I avoid this problem?  Thank you very much!

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  • FormerMember
    +1 FormerMember
on Nov 17, 2022 9:02 PM

Hello,

See snip below. There is only a maximum load that the part can provide with respect to the input voltage

  • Hello, When I try to increase the load value to reduce the load current. It is true that the two output voltages reach the design value. Why is the load current related to the input voltage? Is there any related article? I want to learn this knowledge. Thank you very much.

  • FormerMember
    0 FormerMember on Nov 20, 2022 7:08 PM in reply to LeiShen1996

    This is because of the switch current stress. Since this is a monolithic IC, the inductor and power switches are integrated to the device and can only handle a defined amount of current stress.

    You can review the formulas for the topologies of DC-DC converter and see how it affects the component stresses.

    Regards,

    Jhun

  • Reply
    • FormerMember
      0 FormerMember
    on Nov 20, 2022 7:08 PM in reply to LeiShen1996

    This is because of the switch current stress. Since this is a monolithic IC, the inductor and power switches are integrated to the device and can only handle a defined amount of current stress.

    You can review the formulas for the topologies of DC-DC converter and see how it affects the component stresses.

    Regards,

    Jhun

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