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Original question:

LM5175: Use LM5175 with variable output voltage / output current

LM5175: LM5175

Cora Ferrer
Prodigy 80 points
Part Number: LM5175
Other Parts Discussed in Thread: INA213, , LMV431, LM431

Hi,

I'm facing a very similar design as in https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/561652/lm5175-use-lm5175-with-variable-output-voltage-output-current thread.

The concept schematic answer was really helpful "Visio-LM5175 Variable VOUT and IOUT_General.pdf", but still I would need some support understanding this design and how the resistors values should be calculated, so I can adapt it to my needs.

In this case we just want to use it as a variable output current, for example.

Thank you! 

  • 0
    TI__Mastermind 42661 points

    Hi Cora,

    thank you for using the E2E forum.

    in the power stage designer user guide (https://www.ti.com/lit/pdf/SLVUBB4A) Chapter 8 and 9 there are some more details and calculation examples for that.

    You can also download the tool itself: POWERSTAGE-DESIGNER Design tool | TI.com

    to use this features from there.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    Prodigy 80 points

    Hi Stefan,

    Thanks for your quick answer and the useful links!

    Could you help me understanding the circuit on the .pdf? How does the INA213 and the whole feedback loop works together with the LM5175 ISNS+/-? Would be very helpful and clarifying.Nerd

    Thank you!

  • +1 in reply to Cora Ferrer
    TI__Mastermind 42661 points

    Hi Cora,

    i assume you know how the control on the FB side does work so base my description on that.

    This is covered the the Power Stage designer users guide very well.

    If you need more details on that just let me know.

    So for the current sense (ISNSN and INA 213)

    - the INA213 does amplify the voltage across the current sense resistor with the in the pdf given amplification.

    - with the voltage divider this is then set down to the control voltage level of the LMV431 

    - the resistor from the left side with V_CTRL does allow some modification (same as for the FB signal)

    - the LM431 is a voltage controlled current source, so with the the voltage generated by the INA213 and the divider the current through the resistor on R_Sense is controlled.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    TI__Mastermind 42661 points

    Hi Cora,

    I have not seen an update on this thread for the last 7 days.
    So I assume the issue is solved.
    In this case it would be great to press the is solved button.

    If there is still something open, just let me know with the new details.

    Best regards,
     Stefan