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LM25118: New design request

Jimmy WANG
Genius 3135 points
Part Number: LM25118
Other Parts Discussed in Thread: LM5176

Hi team,

My customer wants to design a programming power.

Vin=7V

Vo=5~9V adjustable output voltage

Io=1~1.5A

I choose LM25118 for a suggestion. Do you have any suggestions for designing an adjusted output voltage? Thanks 

  • 0
    TI__Genius 16245 points

    Hello Jimmy,
    Thanks for reaching out to us via e2e.

    If you want to change the output voltage, you can feed an extra current into the LOWER resistor of the feedback divider.

    It is possible to manipulate the LOWER resistor of the feedback divider.
    Do not dynamically change the upper resistor, as this would have a negative impact on the compensation.

    Please be aware that the FB input is very sensitive to noise, so it is not recommended to simply run some wires through a device (e.g. from the PCB to a potentiometer).
    Possible options for a long-distance control are: a DAC, a digital potentiometer (I2C controllable), different resistors in parallel which are enabled by a FET or some other circuitry which will de-couple the sensitive FB signal.

    Any of these extra components shall be placed as close to the FB pin as possible.

    The Powerstage Designer tool can help to assist with some of these concepts:
    www.ti.com/.../POWERSTAGE-DESIGNER
    Please check out the Dynamic Output Voltage Scaling section.

    Best regards,
    Harry

  • 0 in reply to Harry Hofner
    Genius 3135 points

    Hi team,

    Got it. thanks for your suggestion which device is suitable? 

  • 0 in reply to Jimmy WANG
    TI__Genius 16245 points

    Hello Jimmy,

    The LM25118 that you have mentioned would work. The LM5176 could also be used.

    Best regards 
    Harry