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WEBENCH® Tools/LM3673: USE LOAD SWITCH NOT AVAILABLE IN TI WEBENCH DESIGNER TOOL

pragash sangaran78
Genius 3510 points
Part Number: LM3673
Other Parts Discussed in Thread: TPS65581

Tool/software: WEBENCH® Design Tools

Dear friends,

I'm trying to design power management for my embedded system. There are two supply voltages in my design which is 3.3V and 1.8V. 3.3V is used by one peripheral whereas 1.8V is shared by 3 peripherals. To lower the design cost, i want to be able to use one regulator (for 1.8V) and switch the other unused peripherals off to save power. Meaning, im trying to supply three 1.8V peripherals using one voltage regulator so i want to be able to switch off and on different peripheral voltages independent of each other. 

i think "use load switch" option in the TI power Architect designer helps us to do that. However, when I entered my source and load voltages and currents in TI power Architect designer, "use load switch" option is not available to select! Please refer to the attachment.

Please help!

  • 0
    TI__Genius 14455 points
    Hi Pragash
    To enable the "Use load switch" option, you can click on the sequencing requirement buttom on the top right. Just put a dummy sequencing requirement. This will cause the "Use Load switch" to be enabled. In the future, we will enable this for all conditions. But for now, you can use this.

    Regards,
    Gerold
  • 0
    TI__Intellectual 1490 points

    Dear Pragash,

    "Use Load Switch" option is only enabled when we have sequencing requirement for the loads in Power Architect.

    Please enable sequencing option (Click on sequencing button at the top right of the loads list and select "Up Sequence" check box. You may also clock on "Sequence : UP = Any order, Down = Any order" to get to the same view). Once you enable sequencing you will be able to select "Use Load Switch" check box. This option will add load switch to your required rails. If sequencing is not important for your design - you may chose to ignore the LDO and Sequencer IC in the power tree.

    Regards,

    Srikanth Pam | Online Design Tools

  • 0 in reply to Gerold Dhanabalan - Online Design Tools
    Genius 3510 points
    Dear Gerold,
    i just realized that the issue is not resolved. what i was looking to do is to design power management with one DC to DC converter for three 1.8V voltages as above. So the DC to DC converter should have one input (Vin) and and three output (Vout). how to do that using TI webench power designer
  • 0 in reply to pragash sangaran78
    TI__Intellectual 1490 points

    Pragash,

    If I understand your question right - you would like to use a PMIC (one input and 2 output DC-DC) to supply three 1.8V loads and each of the 1.8V rail should have a separate load-switch. We do not have the feature in Power architect - where you can specify the list of loads to be supplied from a single PMIC. You may see PMIC solutions by clicking on "Get PMIC/PMU Solutions" in the tree solutions listing page - this provides you with options of power trees with PMICs for some rails - but does not guarantee that specific loads are all supplied by single PMIC.

    You can force a load to be a separate supply, by clicking "Separate supply" check-box in the load list. You may also consider using single output regulator for the three 1.8V loads (If this meets your requirement) using three load-switches as below.

    Tree with single supply for 1.8V loads:

    If using a single output DC-DC  does not meet the requirements - you may search for the right PMIC IC on ti.com and use evaluation board and spice model as your starting point for your design. 

    Regards,

    Srikanth Pam| Online Design Tools

  • 0 in reply to Gerold Dhanabalan - Online Design Tools
    Genius 3510 points
    Hi Gerold,
    here is some examples of kind of regulator im looking at.

    cds.linear.com/.../35451fb.pdf

    www.st.com/.../en.CD00159862.pdf

    www.nxp.com/.../MC34VR500.pdf

    i couldnt find a regulator which i can switch off a supply independent of each other. im still looking for it. if you have something equivalent at TI, please let me know. is there anyway to get this kind of regulators using TI webench designer? if yes, please let me know how! thanks.
  • 0 in reply to pragash sangaran78
    TI__Intellectual 1490 points
    Pragash,

    This triple BUCK PMIC - TPS65581 may fit your needs. This part has separate enable pins for each output. But this part is not supported in TI Webench designer. You may use the evaluation board design and PSpice model available in the "Tools and Software" section in the product page as a starting point for your design.

    Regards,
    Srikanth Pam | Online Design Tools
  • 0 in reply to Srikanth Pam
    Genius 3510 points
    Dear Srikanth,
    I have couple of questions:
    1) So multi output boost or buck is not supported in TI webench designer?
    2) what is the advantages and disadvantages of using multi output regulator vs separate single output regulators? which one does TI recommends? Eventhough using multi output sounds good, I worried about delay in timing to enable and disable individual outputs. For instant ON/OFF of a particular regulator, probably it’s the best to use multiple single output regulators. Please drop your input on using multi output regulator vs separate single output regulators. Thanks.
  • 0 in reply to Srikanth Pam
    Genius 3510 points
    TPS65581 has very high input voltage of 4.5V to 20V. My input voltage is 3V to 4.35V, due to this i dont think this IC will suit my application. thanks for suggesting it.
  • 0 in reply to pragash sangaran78
    TI__Intellectual 1490 points
    Pragash,

    For your input voltage requirement - I believe www.ti.com/.../lm26484 may fit your requirements. This is very close to the example parts you mentioned above.

    As for your other questions -
    1) Yes, you are right, we do not have a wide support for PMICs in WEBENCH (There are some PMICs supported, but it seems they wont be suitable for your requirements. For example: www.ti.com/.../lm10502 )
    2) Using Integrated PMIC solution would save your board space and cost compared to using discrete converters for each load. I do not think there will be any major differences in-terms of ON/OFF delays - the startup and shutdown times should be comparable. Also I recommend you to start a new thread for part recommendations if you are not happy with the above solution.

    Regards,
    Srikanth Pam | Online Design Tools
  • 0 in reply to Srikanth Pam
    Genius 3510 points
    Dear Srikanth,
    thanks fo your reply and suggestions. i was looking at separate regulators for each voltage but since you have confirmed there will be no much difference in the performance, i will be looking for single PMIC which can supply three 1.8V and one 3.3V as you can see in my requirement.

    LM2684 is good but only has three output and im not sure if it can switch on and off individual supplies independent of each other.

    thanks for the suggestions.