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LM5050-2: difference with TPS2412 at 12V system

Peter Liu
Prodigy 10 points
Part Number: LM5050-2
Other Parts Discussed in Thread: TPS2412, LM5050-1

Dear TI Engineers,

I want to design an ORing circuit with 12VDC output. LM5050-2 has the wide input voltage range from 6V to 75V. Is LM5050-2 suitable to be used in 12V system? What is the diference between LM5050-2 and TPS2412.

And on page 13 of LM5050-2 DATASHEET, it recommends Logic level MOSFETs to build the circuit, coult you pls tell what exactly Logic level MOSFETs is?

THANKS!

  • +1
    TI__Guru 57737 points

    Hi Peter,

    Welcome to e2e !

    Both TPS2412 and LM5050-2 can block reverse current and hence can be used in ORing Configuration.

    • As you mentioned,  LM5050-2 has wider input voltage range when compared to that of TPS2412. 
    • TPS2412  has adjustable reverse voltage threshold (Adjustable turnoff threshold).

    If you can give more information on your end application and specifications, I can help you choose the right part between the two.

    Here, Logic level Mosfets corresponds to the Gate-Source voltage required to turn ON the Mosfet, i.e. a 3.3V or 5V at the gate-Source of the FET can turn ON the FET. 

  • 0 in reply to Praveen GD
    Prodigy 10 points

    Hi, Praveen,

    Got it !! And I would like to learn more about that.

    1, So, the FET with Vgs=3.3V or 5V  is Logic level MOSFET. What about Vgs is anyother voltage values between 3.3~5.0V? Do FETs with Vgs=4.0V or 4.5V belong to logic levle FET? What is sub-Logic level MOSFET?

    2, We are designing a power supply circuit with the output of 50V/30A, and want to use LM5050-2 to build ORing circuit. So what kind of FET is suitable? With Vgs≤5V, Rds(on)=2mΩ? Is it necessary to use Linear FETs? We prefer standard FET to Linear FET because of the price.

    3, We have another circuit with the output of 12V/13A, and also have to build ORing circuit. We prefer LM5050-2 to TPS2412, but we concerned about performance of LM5050-2 at 12V system. TPS2412 focus on low voltage level, dose it perform better than LM5050-2 at 12V system.

    Thank you!

  • +1 in reply to Peter Liu
    TI__Guru 57737 points

    Hi Peter,

    Please see my response below,

    1. Sub-Logic level MOSFETs have gate thresholds around 2V or 1.2V. LM5050-2 is capable of driving MOSFETs with both logic and sub-logic level gate thresholds. Basically any FET with gate threshold < 5V which covers most of the FET available in the market. 

    2. In ORing applications, FET SOA is not critical. So, you can consider using a standard/ switching FET as well. You can follow the recommendations in datasheet, section 'MOSFET SELECTION' for understanding different about important parameters in Mosfet selection.

    3. LM5050-2 performance will not be degraded when operated at a lower voltage of 12V. You can expect consistent performance of LM5050-2 across operating input voltage range. For detailed analysis, you can refer to the characterization plots in 'Typical Performance Characteristics' section of the datasheet. 

  • 0 in reply to Praveen GD
    Prodigy 10 points

    Hi, Praveen,

    Thank you so much. It really helps me a lot.

    And about LM5050-1, do LM5050-1 and LM5050-2 have the same performance in the ORing circuit?

    LM5050-2 has FET Test Mode. I am curious about how to use it, because if we active the FET Test Mode wtih heavy load, the FET will be turned off, and all current will flow through the body diode, which result in a large power loss. In my opinion, it is dangerous that we active FET Test Mode when the output current is huge. But if we can't figure out whether the FET is shorted or not without output current. So how do we use FET Test Mode in a safe way. And if we don't use FET Test Mode,  we just let nFGD pin float, is that right?

  • 0 in reply to Peter Liu
    TI__Guru 57737 points

    Hi Peter,

    Let me get back to you by early next week.

  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi Peter,

    Yes, LM5050-1 and LM5050-2 have the same performance in the ORing configuration. 

    Generally, FET body diodes are capable of handling the same current as that of the channel for shorter durations of time. You can use the FET Test Mode for time long enough for your Micro Controller to detect the nFGD output (to analyze the FET status) but also short enough time not to cause overheating of the FET. If not used, the nFGD can be left floating. 

  • 0 in reply to Praveen GD
    Prodigy 10 points

    Hi, Praveen,

    Thank you so much! There are two editions of LM5050-2, LM5050MK-2 and LM5050MKX-2. What are the differences between two editions?

  • 0 in reply to Peter Liu
    TI__Guru 57737 points

    Peter,

    The only difference between the LM5050MK-2 and LM5050MKX-2 is the Package Quantity.