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TINA/Spice/TPS40428: tps40428 design

Bruce Llin
Prodigy 140 points
Part Number: TPS40428
Other Parts Discussed in Thread: TINA-TI, , CSD95378BQ5M

Tool/software: TINA-TI or Spice Models

FW a new high current DC- DC power convertor - TPS40428.msg

Hi TI Expert

we are looking for a new power DC- DC power convertor, for the application of tps40428, I have some question need you help:

1. For TPS40428, what the maximum current each phase can support, 25A or 30A?  on page 1 main description, TPS40428  can support 4 phase to 120A, which mean 1 phase can support 30A, However, on page 78/79, test waveform and data only show 25A, which one is correct?

 

 2.  On page 7, the output overcurrent fault as below picture showing, which is for 1 phase output, right?

 

3.  As you know, TI WEBENCH@Designer tools recommend TPS40428+ 2pcs CSD95378BQ5M (Mosfet),

    CSD95378BQ5M’s VDD and Enable voltage range is 4.5 ~ 5.5V, However, no 5V output voltage on my board,

     so can we divider 12V Vcc to 5V to it, do you think it’s ok?

 

4.  Below picture show the main power dissipation,  seems 2pcs mosfet’s  power dissipation is up to 4.6W, need we add another heat-sink?

junction-to case thermal resistance is about 15C/W and junction-to board thermal resistance is about 1.5C/W,  

which one is main for this type Mosfet?

 

 5. Is TPS40428 in MP?  Is there any critical issue when other customer use this part

6. How about the draft cost and lead time,  it’s better for me is you can recommend us other good solution.

 

Best Regards,

Bruce Lin

  • 0
    TI__Expert 5965 points
    Hi Bruce,

    For #1, TPS40428 can support 30A for each phase. However, it also depend on the system thermal design. If low temperature is needed then the supported current per phase will be reduced.

    For #2, Yes, the table is showing per-phase current limit.

    For #3, in this case, we recommend to use TPS40428 BP5 as enable voltage for CSD95378B. This way it will guarantee TPS40428 is powered when CSD95378B is enabled.

    For #4, I can not see the picture, but thermal design will depend on system requirement. I'm not sure what's your ambient temperature but usually 2.3W per power is ok without heatsink.

    For #5, Yes, TPS40428 is in MP for 4 years, no critical issue.

    For #6, Please contact TI sales office for pricing and lead time.

    Regards,
    Weidong
  • 0 in reply to Weidong Zhu
    Prodigy 140 points
    Hi Weidong,

    thanks for your quick reply, which help me a lot, I still have some question need you help:

    For #2, base on page 7 of datasheet and your reply, per-phase current limit is 40A (factory default settings), and the value can also change to 50A by i2c bus, so two phase can support up current limit 80A (factory default settings), which maximum current is up to 100A, right?

    our now desing is :
    VIN = 12V
    Vout = 0.85V (nominal)
    Current = 70A Max

    Can we use 2 phase TPS40428 when working with the Smart FET CSD95378BQ5MT, do you think have any risk for my design?
    especilly long time run.

    offcourse, we will add some heatsink on Smart FET CSD95378BQ5MT when actually application.

    I also use TI demon board to do some testing, seems Smart FET CSD95378BQ5MT's thermal rise is about 40C when 2 phase TPS40428 working with the Smart FET CSD95378BQ5MT on 70A.


    best regards,
    bruce
  • 0 in reply to Bruce Llin
    TI__Mastermind 24075 points

    Hi Bruce,

    The OC fault limit is 40A (inductor peak current) per phase in factory default, and it can be changed to 50A per phase by PMBus.

    For 2phase 70A design, the concern is power stage (CSD95378B) thermal. If the ambient temperrature is high, the power stage will be hot.

    The power stage uses its power pad for heat dissipation, adding headsink on its top case does not help much.

    I sugest you to use EVM to do some test. If the test result show power stage temperature looks fine, it should be ok to go with 2phase for 70A design.

    Also, TPS40428 BP5 can not be used for power stage VDD (5V), because BP5 sourcing capability is not large enough. A small LDO is suggest to converter 12V to 5V for power stage VDD.

    Thanks

    Qian

     

  • 0 in reply to Qian Chen
    Prodigy 140 points
    Hi Qian,

    thanks for your information, which make us more clear.

    one more question:
    as you know, power stage (CSD95378B)'s TAO pin is connect to tps40428 TSNS, I try to use Fusion Digital Power Designer to
    monitor some parameter, such output voltage, current, for the temperature, is power stage (CSD95378B)'s junction temperature, right?
    if yes, seems ok to go with 2phase for 70A design base on my test result.

    Best regards,
    Bruce
  • 0 in reply to Bruce Llin
    TI__Mastermind 24075 points

    Hi Bruce,

    TPS40428 obtains the temperature signal from power stage TAO pin.

    The temperature readout in PMBus is power stage junction temperature.

    Thanks

    Qian