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WEBENCH TPS40303

eli
Guru 13485 points
Other Parts Discussed in Thread: TPS40303, CSD16325Q5, SWITCHERPRO

When creating design for TPS40303 for Vin=3.3V, Vout=1.00V/20A

1)I am not able to choose other  M2 (lower FET), but only M1.Why?

2)Why when choosing ME FET from TI, I can not get any M2 FET from TO too?

3)I choose  M1 as CSD16325Q5 and got Efficiency of 94% ,but when I run this simulation with the SwitcherPro, and would like also to choose CSD16325 for appear FET, I got below  massage:

This MOSFET caused the basic design calculations to fail!

High-side MOSFET Rdson calculation failed.

This device doesn't have a good rdson specifications.

 

  • 0
    TI__Genius 14455 points

    Hi Eli,

        M1 and M2 FETs are arranged as pairs and should have the combination of FETs that you are looking for. If a particular FET gets selected as M1 and not as M2 (in the entire list), the possibility is that the FET could not be used as M2. This is because depending on the duty cycle (especially lower duty cycles), the RMS current through the low side FET M2 was larger causing heating up of the FETs and cannot be used in the application.  We no longer support SwitcherPro and we currently recommend using WEBENCH for your design needs. Regarding your concern of not being able to select CSD16325Q5 as M2, we are looking into that and we will get back to you once we have a solution to it.

    Regards,

    Gerold

     

     

  • 0
    TI__Expert 6365 points
    Hey Gerold,
     
     
    Reparse the Schematic to see if it fixes the problem.  
     
    Regards,
    Howard
     
     
    From: Gerold Dhanabalan - WEBENCH Design Center [mailto:bounce-1132529@e2e.ti.com]
    Sent: Monday, July 15, 2013 12:40 PM
    To: switcherpro@e2e.ti.com
    Subject: RE: [Power and Lighting Tools Forum] WEBANCH TPS40303
     

    Hi Eli,

        M1 and M2 FETs are arranged as pairs and should have the combination of FETs that you are looking for. If a particular FET gets selected as M1 and not as M2 (in the entire list), the possibility is that the FET could not be used as M2. This is because depending on the duty cycle (especially lower duty cycles), the RMS current through the low side FET M2 was larger causing heating up of the FETs and cannot be used in the application.  We no longer support SwitcherPro and we currently recommend using WEBENCH for your design needs. Regarding your concern of not being able to select CSD16325Q5 as M2, we are looking into that and we will get back to you once we have a solution to it.

    Regards,

    Gerold

     

     

  • 0
    Guru 13485 points
    Hi Gerold,
    Why non of the M2 options are TI device?
    Its looks strange for me that non of TI FETs can be used as M2,which is not correct if you looks at the EVM!
    B.regards
    Eli.
     
    -----------------------------------------------------
    Eli Shtuden
    TELSYS LTD
    Tel: 972 3 7657635
    Mobile:972 50 5262996 
     
    From: Gerold Dhanabalan - WEBENCH Design Center [mailto:bounce-1132529@e2e.ti.com]
    Sent: Monday, July 15, 2013 10:40 PM
    To: switcherpro@e2e.ti.com
    Subject: RE: [Power and Lighting Tools Forum] WEBANCH TPS40303
     

    Hi Eli,

        M1 and M2 FETs are arranged as pairs and should have the combination of FETs that you are looking for. If a particular FET gets selected as M1 and not as M2 (in the entire list), the possibility is that the FET could not be used as M2. This is because depending on the duty cycle (especially lower duty cycles), the RMS current through the low side FET M2 was larger causing heating up of the FETs and cannot be used in the application.  We no longer support SwitcherPro and we currently recommend using WEBENCH for your design needs. Regarding your concern of not being able to select CSD16325Q5 as M2, we are looking into that and we will get back to you once we have a solution to it.

    Regards,

    Gerold

     

     

  • 0 in reply to eli
    TI__Genius 14455 points

    Hi Eli,

         We agree that TI FETs should get selected for M2 as well. We are currently looking into why TI FETs are not getting selected for M2 and will let you know once we have found a solution.

    Regards,

    Gerold

  • 0 in reply to Gerold Dhanabalan - Online Design Tools
    TI__Genius 14455 points

    Hi Eli,

         Please give it a try now. You should be able to select TI FETs now. However, you might not see all possible combinations listed because the tool narrows done a huge list of possible permutations to a finite list. Please let us know if you have further questions.

    Regards,

    Gerold