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  • TI Thinks Resolved

DC/DC converter with adjustable output Voltage

Hello,

i am looking for an DC/DC Converter.

Inputvoltagerange from 24V to 36V

Outputvoltagerange from 4V to 23V

Outputcurrent from zero to 5 A

I need three of these Outputs in my circuit.

It would be great when we could monitor voltage an current from the output.

Many thanks for the support

Philipp

  • Hello Philipp,

    I see this is your first post so welcome to E2E!  For the design parameters you have given, a question about the output voltage: do you want this to be continuously variable?  Or will you select a fixed voltage within that range? 

    I invite you to engage WEBENCH Power Design: www.ti.com/design-tools/overview.html .  With the parameters you stated (and I selected a 23VOUT), I see about a dozens designs that could be used; I encourage you to go through the WEBENCH process yourself, determine in these designs what is most important (pcb size, efficiency, etc) and proceed from there. 

    Let us know what you determine.

    Regards,

    ~Leonard  

  • In reply to LeonardEllis:

    Hello Leonard,

    we need the power out continuously variable. In the application we need different Voltages from batch to batch. It would be nice to set the voltage digitaly.

    Regards

    Philipp
  • In reply to user507251644:

    I would probably start by looking at a wide duty cycle voltage mode controller such as LM25145. Maybe use a digital potentiometer for the lower FB resistor.

    Best  Regards,

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

  • In reply to user507251644:

    Hello Philipp,

    Here is a TI Design that uses a DPOT, (TPL0401A-10), to set the output voltage.
    It would be applicable to any controller or converter that uses classic resistive divider feedback.

    TIDU533 TI Designs Power Supply with Programmable Output Voltage and Protection for Position Encoder Interfaces


    Best Regards,

    Ed Walker
    Texas Instruments 
    Online Support - Systems & Tools

     

  • In reply to EdWalker:

    Hello,

    yes that sounds good with the potentiometer an the LM25145. But at the Linear Side i saw the LTC3884/-1 that comes with all that features exept the voltage range. So is there maybe a chip von TI with the right range and with wide duty cycle range?

    Iam not so familiar with the design of DC/DC converter. So witch points do I have to keep in mind so that the controller is stable over the whole area.

    Regards

    Philipp

  • In reply to user507251644:

    LM25145 uses voltage mode control. For voltage mode control, the lower FB resistor is not considered in the ac analysis, so you can vary the low side resistor to change the output voltage without affecting the stability.

    Best  Regards,

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

  • In reply to user507251644:

    Hello User,
    The LTC3884 is a PMBus dual phase controller.
    PMBus is an I2C derivative for a digital management of power supplies.
    TI has many PMBus controllers as well.
    This link will show buck controllers and converters with PMBus or I2C
    www.ti.com/.../products.html

    These applications are targeted for lower voltage system board designs.
    You are looking for a Vout max of 23V, which will be very hard to find today.
    With the link I provided you can sort by VOUT MAX, highest to lowest, and see what TI has for PMBus/I2C by Vout.
    None will meet your 23Vout requirement.

    Your best solution is to use the LM25145, as John Tucker recommended.
    Control the Vout using a Digital Potentiometer.

    www.ti.com/.../products.html

    TI's Digital Pots are available in:
    single or dual per package
    linear or logarithmic taper
    SPI or I2C control
    10Kohms or 100Kohms 'end to end resistance'
    64, 128 or 256 steps
    Some also have Non Volatile memory, meaning once you set them the setting will be retained when power is cycled.


    Best Regards,

    Ed Walker
    Texas Instruments 
    Online Support - Systems & Tools

     

  • In reply to EdWalker:

    Hello Ed,

    thanks for the information. I had the hope that there is an Ic with the spec that i didnt find.

    So when i search for buck converters i also get the LM73605. I think this IC would be mutch easier for the Layout then the LM25145.
    Is that a good Idea or did i miss something?

    Regards

    Philipp
  • In reply to user507251644:

    Hi Philipp,

    The LM73605 36V, 5A converter with integrated FETs is suitable for your application. Its Toff-min of 70ns allows you to meet the 24Vin to 23Vout conversion at 350kHz.

    Regards,
    Tim
  • In reply to Timothy Hegarty:

    I concur with Tim. Integrated FET converters are easier to layout due to fewer components.
    EMI performance is also enhanced with small current loops made possible by integrating the Mosfets.


    Best Regards,

    Ed Walker
    Texas Instruments 
    Online Support - Systems & Tools

     

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